Prof Pierre-Henri Aubert

Dr Mery Stéphane

Dr Heinrich Benoît

Dr Teng Teng

Dr Han Shuaiyuan

Dr L I Yan

Dr Auffray Morgan

Summary

After the discovery of the conductivity property of polyacetylene by A. J. Heeger, A. G. MacDiarmid, and H. Shirakawa, 1 in 1977, organic π-conjugated systems and particularly polymers, have been intensively studied. Since then, many leading research groups have designed, synthesized, and investigated the charge transport properties of numerous different organic semiconductors (OSCs), to eventually incorporate them in specific electronic devices, and to replace the well-known inorganic semiconductors, such as silicon.

Indeed, these OSCs are attractive essentially because they can take advantage of organic material properties, such as lightweight, potentially low cost, and efficient thin-film and flexible device fabrication. Consequently, nowadays, OSC molecules and macromolecules are already introduced as active layers in electronic components such as organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), and organic field-effect transistors (OFETs).

To design these OSC materials for specific applications, it is important to understand how chemical modification alters electronic and photophysical properties and several strategies have emerged as highly effective means to accomplish this goal. Incorporating electron-withdrawing substituents onto the periphery of -systems can improve the oxidative stability of these organic structures while increasing electron affinity. The replacement of elements (particularly bridging elements within the system) also serves as an effective means to alter the electronic structure and influence packing in the material. Finally, ring fusion to afford polycyclic aromatic systems can alter frontier orbital energies and tune the bandgap. These strategies have all been used in conjunction with cross-coupling to create a wide range of conjugated polymers. This is why in this thesis, chapter 1 provides a general introduction describing the design principles and controlled synthesis method for tuning electronic properties of conjugated organic semiconducting polymers. Subsequently, we present in chapter 2 (respectively chapter 3) the design, synthesis, and characterization of new polymers tested as alternatives for OFETs (respectively OLEDs).

More precisely, chapter 2 deals with the design, synthesis, and characterization of new structured π-conjugated polymers for OFETs applications. Indeed, in this context, charge-carrier transport properties depend not only on the intrinsic electronic properties of the materials, but also on the way the molecules are packed together in bulk. Therefore, one of the key parameters to improve the performance of such organic based components is the development of structured and/or more ordered π-conjugated systems. Representative technological examples are the area of organic microelectronics where patterning of p-and n-channel semiconductors is one of the major hurdles for the implantation of OSC in an organic complementary logic circuit. The first part is dedicated to the bibliography in this specific field, with an emphasis on a class of organic π-conjugated systems able to give spontaneously self-assembling, i.e. organic liquid crystals. In the second part we describe the synthesis and the characterization of two novel side-chain liquid crystal (SCLC) semiconducting polymers where: (i) the backbone is a π-conjugated polymer and (ii) the side groups are π-conjugated calamitic or discotic mesogens. Then we discuss the supramolecular architecture resulting from the phase separation, at the nanoscale level, of these two covalently linked π-conjugated systems that we expect to be able to self-organize in bulk. The charge transport properties of these two innovating polymers are also discussed.

Similarly built to the precedent one, chapter 3 deals with the synthesis and the study of new TADF-based (Thermally Activated Delayed Fluorescence) π-conjugated polymers specifically designed for OLEDs applications. Indeed, TADF emitters are the third generation of organic building blocks that are currently investigated for organic lightening. As a consequence, several macromolecular architectures have been investigated to try to obtain efficient TADF properties during the second part of the Ph.D. project. First, two series of new TADF polymers based on a donor (D) backbone and twisted acceptor (A) side-groups have been targeted. Second, interesting new types of TADF polymers based on through space D-A interactions have been designed. Thus, after describing the synthesis of all these D-A polymers, their photophysical properties such as photoluminescence quantum yield (PLQY) and fluorescence lifetime in both solution and solid-state have been carried out, to determine if they are TADF or not. The electroluminescence properties of these materials in OLED configuration have been measured as well, and preliminary EQE results are reported. The fabrication of optimized devices is also currently in progress and will be discussed.

Chapter 1 General introduction to π-conjugated polymers

Organic semiconductors (OSCs), i.e. π-conjugated small molecules or polymers, have attracted researchers' attention due to their fascinating electronic and photophysical properties. These types of materials have been incorporated into a wide variety of electronic devices since they are lightweight, solution-processable, flexible, and they possess tunable properties.

To design conjugated materials for different applications, it is important to understand how chemical modifications alter electronic and photophysical properties, and several strategies have emerged as highly effective approaches to accomplish this goal. As an example, incorporating electronwithdrawing substituents onto the periphery of π-systems can improve the oxidative stability of these organic structures while increasing electron affinity. The replacement of elements (particularly bridging elements within the π-system) also serves as an effective means to alter the electronic structure and influence packing in the material. Finally, ring fusion to afford polycyclic aromatic systems can alter frontier orbital energies and tune the bandgap. These strategies have all been used in conjunction with new synthetic tools and methods, such as cross-coupling, to create a wide range of conjugated polymers. This is why in chapter 1, after a general introduction to the field, we will discuss some design principles for tuning electronic properties of π-conjugated organic semiconducting polymers, before to describe as well some specific controlled synthesis methods.

General background on organic electronics

The term "Organic Electronics" describes the general field of synthetically derived π-conjugated materials that exhibit the electronic attributes of conductors or semiconductors. These unique materials bring promise for a new generation of cost-effective, lightweight, flexible, and functional electronics.

While there are a variety of new application spaces for these materials that continue to emerge, the core applications include organic light-emitting diodes (OLEDs) [START_REF] Burroughes | Light-Emitting Diodes Based on Conjugated Polymers[END_REF] , organic field-effect transistors (OFETs) [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] , organic photovoltaics (OPVs) [START_REF] Wang | Organic Semiconductor Crystals[END_REF] , electrochromic devices (ECDs) 5 and photodetectors [START_REF] Chen | A Flexible UV-Vis-NIR Photodetector Based on a Perovskite/Conjugated-Polymer Composite[END_REF] .

As a remark, these organic electronic devices typically trail behind their inorganic counterparts in terms of performance, but instead offer numerous advantages including mechanical flexibility [START_REF] Yi | Ultra-Flexible Solution-Processed Organic Field-Effect Transistors[END_REF] , adaptability to low-cost processing techniques [START_REF] Søndergaard | Roll-to-Roll Fabrication of Large Area Functional Organic Materials[END_REF] , synthetic tunability [START_REF] Liang | Highly Efficient Solar Cell Polymers Developed via Fine-Tuning of Structural and Electronic Properties[END_REF] , and biocompatibility [START_REF] Rivnay | The Rise of Organic Bioelectronics[END_REF] , providing a competitive edge in both commodity and niche markets.

On the commodity side, the ability to formulate liquid inks out of organic electronic materials opens up manufacturing possibilities through low-cost printing techniques such as screen-printing, blade coating, inkjet printing, rotogravure printing, aerosol spray coating, and slot-die coating. Many of these techniques are amenable to roll-to-roll (R2R) processing, in which reels of the substrate are continuously moved through the coating, drying, laminating, and cutting processes similar to what is done in the graphic printing industry. The high throughput nature of R2R processing reduces the costs associated with manufacturing, allowing for simple electronic devices including sensors, logic circuits, photovoltaics, etc. to be produced more rapidly and at lower costs than electronic components composed of inorganic materials such as doped silicon.

On the niche side, the ability to print onto a variety of substrates opens up opportunities for the integration of electronics into plastic and paper-based products. Additionally, the ability to create flexible electronics can reduce the design limitations caused by rigid electronic components. Synthetic tunability of organic electronic materials allows for components to be made transparent or in a variety of colors. Finally, designing for biocompatibility can lead to new ways for electronics to interface with living systems.

For these reasons, research in organic electronics is not solely focused on increasing performance metrics to compete with traditional electronics, but is also focused on exploring the properties and processing methods that cannot be achieved through inorganic materials.

Fundamental concepts and mobility drawback

Organic electronic materials, whether molecular or polymeric, exhibit interesting optical and electronic properties, relying on the ability to move electrons through π-conjugated structures, which consist of alternating single bonds and double bonds that create a plane of sp 2 hybridized orbitals with 2pz orbitals left perpendicular to that plane. These 2pz orbitals overlap to form a network of π bonds that can move electrons across the plane of conjugation.

For instance, as represented in Figure 1. 1, cis-/trans-polyacetylene is a linear polyene with a πconjugated system, consisting of a long chain of carbon atoms with alternating single and double bonds between them, each with one hydrogen atom. And poly(para-phenylene) (PPP) and poly(paraphenylene vinylene) (PPV), containing a phenyl ring in their repeat units, are two kinds of typical light-emitting polymers. The impact of increasing the extent of conjugation on electronic properties can be well understood by the progression from ethylene to butadiene, octatetraene and further to varying lengths polyenes. As shown in Figure 1. 2, with an increasing number of overlapping 2pz orbitals, there is a decrease in the energetic bandgap (Eg) between the highest occupied molecular orbital (HOMO) and lowestunoccupied molecular orbital (LUMO) of the system, transitioning these materials from insulators to materials that have similar bandgap between HOMO and LUMO as bandgap between valence bands (VB) and conduction bands (CB) in inorganic semiconductors. If this trend were to continue, it could be assumed that eventually, an extent of conjugation would lead to a negligible bandgap between the HOMO and LUMO, as it is seen between the VB and CB in metal conductors. However, the instability of a quasi-one-dimensional structure of sp 2 hybridized C-C bonds leads to a distortion of the chain to provide stabilization through a lower energy arrangement. [START_REF] Salzner | Comparison of Geometries and Electronic Structures of Polyacetylene, Polyborole, Polycyclopentadiene, Polypyrrole, Polyfuran, Polysilole, Polyphosphole, Polythiophene, Polyselenophene and Polytellurophene[END_REF] Known as Peierl's distortion, the physical effect of this stabilization is seen through bond-length alternation (BLA) of shorter bonds and longer bonds. This stabilization lowers the HOMO and raises the LUMO, preventing conjugated materials from achieving the zero-energy bandgap seen in conducting metals.

Even though conductivity can be achieved in conjugated materials through doping mechanisms, as is the case in PEDOT:PSS, [START_REF] Lövenich | PEDOT-Properties and Applications[END_REF] most conjugated materials are used as semiconducting materials because of this limitation. As a consequence, one of the key drawbacks of organic materials is their relatively low charge carrier mobility compared to inorganics. Charge carrier mobility ( ), defined as the ratio between charge drift velocity ( ) and the amplitude of the applied electric field (E), is effectively a measure of the ability to transport charge across the materials and typically reported in cm 2 •V -1 •s -1 , and therefore plays an important role in semiconductors.

For crystalline inorganic materials, a highly ordered covalent network of atoms allows charges to delocalize into valence and conduction bands. Charges can be easily moved within these inorganic semiconductors, giving mobility values in the range of 10 2 -10 3 cm 2 •V -1 •s -1 . [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] Since organic materials are packed by weak intermolecular interactions (Van der Waals forces, dipoledipole), charges are localized onto single molecules and are transported through a slower "hopping" mechanism. In this mechanism, each molecule contributes discrete molecular orbitals, and charges can move between the frontier molecular orbitals of each individual molecule. In this sense, the array of HOMO and LUMO energy levels contributed from each molecule serve as an analogue to the valence and conduction bands observed in inorganic materials. Charge transport is therefore governed by a diffusion-related "hopping" between charged and neutral molecules, providing organic materials lower mobility values in the range of 10 -5 -10 cm 2 •V -1 •s -1 . This broad mobility range is attributed to the vast differences in molecular structure, intermolecular interactions, and morphology among organic materials. For example, highly pure rubrene single crystals have hole mobility values as high as 40 cm 2 •V -1 •s -1 due to their high degree of crystallinity and lack of grain boundaries, [START_REF] Takeya | Very High-Mobility Organic Single-Crystal Transistors with in-Crystal Conduction Channels[END_REF] while semicrystalline polymers such as P3HT show hole mobility values on the order of 10 -3 -10 -2 cm 2 •V -1 •s -1 .

Organic semiconductors can either transport holes (p-type), electrons (n-type), or both (ambipolar).

Their charge carrier mobility is highly associated with the device performance, it is an important issue to explore high-mobility organic semiconductors.

How to raise mobility in organic materials? Since geometric fluctuations upon charging are related to intramolecular degrees of freedom, rigid molecules are traditionally pursued for high charge mobility systems. [START_REF] Malagoli | Density Functional Theory Study of the Geometric Structure and Energetics of Triphenylamine-Based Hole-Transporting Molecules[END_REF] Fused aromatic systems like polyacenes have low degrees of rotational freedom, thus require small energies for reorganization. For example, by restricting torsional rotation, naphthalene demands less reorganization energy ( 100 meV) than biphenyl. In addition, efficient packing increases the charge transfer integral and allows for the formation of an ordered network analogous to the covalent lattice seen within inorganic systems. Hence rigid molecules with a highly planar structure benefit from both small reorganization energy and the capability to closely pack in the solid-state. Using this design approach, organic molecules with hole mobility values on the order of 10 cm 2 •V -1 •s -1 have been successfully developed. [START_REF] Takeya | Very High-Mobility Organic Single-Crystal Transistors with in-Crystal Conduction Channels[END_REF] However, rigid and flat organic materials that can efficiently pack in the solid-state tend to suffer from insolubility and processability. For this reason, a delicate balance is required between solubility and the ability to pack efficiently in the solid-state.

Molecular versus polymeric organic semiconductors

Both molecular and polymeric conjugated materials have been investigated within organic electronics research, and each has its advantages and disadvantages, as summarized in Table 1.1. 1. Discrete molecular materials are monodispersed and can be purified via traditional workups, such as column chromatography, distillation, and sublimation. Though batch-to-batch variations in yield may exist, discrete molecules can be purified to the extent that the final materials will always be identical, facilitating their scale-up and industrial use. Moreover, discrete molecules have a great tendency towards order in the solid-state: creating efficiently packed, crystalline morphologies to gain higher charge mobility. But this high degree of order may cause discrete molecules to easily aggregate in solution, limiting their solution-processability. Owing to this limitation, many high-performance molecular systems are processed through vacuum deposition, a high energy process that is not amenable to R2R manufacturing. Besides, increased crystallinity in the solid-state morphology makes these materials brittle, inhibiting their use in flexible electronics applications, and may create grain boundaries to serve as charge traps. On the contrary, polymeric materials by nature always have a degree of dispersity and their purification is limited to the fractionation of disperse materials through precipitation, Soxhlet extraction, size exclusion chromatography, and continuous spin fractionation. The resulting variations in molecular weight and dispersity are not trivial and can have impacts on both optoelectronic and mechanical properties. In addition, the dispersity, chain entanglements, chain-ends, and existence of both amorphous and crystalline solid-state domains in polymeric systems inherently lead to a certain degree of disorder in solid-state morphology, which can be viewed as both an advantage and a flaw.

For one thing, the disorder is beneficial for solubility, processability as well as mechanical malleability, facilitating their use in flexible electronics applications. For another, the disorder can disturb intermolecular interactions between conjugated backbones and create charge traps, leading to decreased charge mobility.

All that being said, many of these differences between molecular and polymeric materials are continuously becoming blurred. The solubility and mechanical flexibility of discrete molecules are improved by being made larger and incorporated with long aliphatic solubilizing chains, while conjugated polymeric systems with rigid backbones are achieving high charge mobility values that rival crystalline discrete molecules. Advancements in living polymerization of conjugated polymers through chain transfer coupling techniques are also leading to polymeric materials with low dispersity, decreasing the drawbacks from batch-to-batch variations.

While discrete molecular systems have obvious merit in the field of organic electronics, the objectives of this thesis project lend itself to focus on polymeric systems, which will be further discussed in this chapter.

A brief history of conjugated polymers

Discovery. The earliest research into conjugated polymers dates back to the 1960s, with Donald Weiss and coworkers observing electronic properties in doped polypyrrole, [START_REF] Mcneill | Electronic Conduction in Polymers. I. The Chemical Structure of Polypyrrole[END_REF] and the work of René Buvet and Marcel Jozefowicz on doped polyaniline. [START_REF] De Surville | Electrochemical Chains Using Protolytic Organic Semiconductors[END_REF] Perhaps the most notable impulsion in this field came from the combined work of Alan MacDiarmid, Hideki Shirakawa, and Alan Heeger on metallic-like conductivity in iodine-doped polyacetylene. 1 Synthesized through Ziegler-Natta polymerization of acetylene, Shirakawa and coworkers observed the formation of a silvery film from the resulting polyacetylene. Though the neutral polymer displayed low conductivities, vapor-doping the films with iodine resulted in an increase in conductivity to ~10 2 S/cm. This seminal work kicked off the field of conjugated polymers and earned these three scientists the Nobel Prize in chemistry in 2000.

In the following decades, research focused on extending the oxidative polymerization of other aromatic units to create conjugated heterocyclic polymers such as polythiophenes. Nevertheless, much of the early work concerning the synthesis of conjugated polyheterocycle was limited to oxidative polymerization along with electro-polymerization of monomers onto an electrode. The resulting conjugated polymers are typically insoluble in their neutral forms, even though their electronic properties could be well investigated, their molecular weights and dispersity were not clear.

In the meanwhile, other conjugated polymers like PPP and PPV synthesized through polycondensation reactions, for instance, Wittig and Knoevenagel reactions, were also insoluble.

Towards conjugated processable polymers. For these reasons, the field has largely moved towards soluble conjugated polymers. Much of this progression in the 1990-2000s focused on the incorporation of side chains (R), typically aliphatic groups, onto the conjugated backbone. This modification not only afforded a final polymer good solubility in organic solvents, but provided a synthetic handle over molecular weight and dispersity. Side chains expanded the toolbox for conjugated polymer chemists and led to new families of soluble polymers based on new aromatic monomers that were previously inaccessible, including fluorene, carbazole, thiophene and its fused derivatives, benzothiadiazole and its derivatives, rylene diimides, and diketopyrrolopyrrole (see structures in Figure 1. 3).

Figure 1. 3

Typical building blocks for conjugated processable polymers: fluorene, carbazole, thiophene and its derivatives, benzothiadiazole, diketopyrrolopyrrole, and rylene diimides.

Good solubility makes it possible for the soluble conjugated polymers to be synthesized through solution-based polymerization methods, notably, Grignard metathesis (GRIM) method and palladiumcatalyzed cross-coupling polymerizations, purified by removing catalyst and salts used/produced in the polymerization through traditional solution-based chemical techniques: it includes precipitation, filtration as well as chromatography, fractionation via Soxhlet extraction to reduce dispersity and obtain batches of varying molecular weight, and characterized in a solution using common techniques (NMR, SEC, UV-Vis, PL, etc.,) to provide structural information that could not be obtained through solid-state analytical techniques. Moreover, good solubility is enabling solution-based processing methods, bringing conjugated polymers into the realm of printed electronics. It is worth mentioning that GRIM method enabled the room temperature synthesis of poly(3-hexylthiophene) (P3HT) with controlled degrees of polymerization and regioregularity, providing researchers with a controlled conjugated polymer "fruitfly" that has served as the basis for understanding structure-property relationships across the field. [START_REF] Loewe | A Simple Method to Prepare Head-to-Tail Coupled, Regioregular Poly(3-Alkylthiophenes) Using Grignard Metathesis[END_REF] Recent evolutions. From the point view of monomer, GRIM method is limited primarily to electronrich aromatic monomers. Thus, progression in palladium-catalyzed cross-coupling reactions (Stille coupling, Suzuki coupling, etc.,) and their extension to polymerizations has largely expanded the scope of monomer breadth to include electron-deficient monomers and has also enabled a host of new conjugated homopolymers and random/block/alternating copolymers. These cross-coupling polymerizations have revolutionized the area of soluble conjugating polymers, providing the tools for organic chemists to design new monomers and polymers with nearly endless possibilities. Despite their efficiency and reliability, we have to keep in mind that these polymers, synthesized by such transition-metal catalyzed coupling reactions, suffer some environmental and performance issues such as the use of hazardous monomers, toxic solvents, or transition-metal catalysts (e.g. Pd, Ni, Fe, etc.,) that end up as residual impurities in the final devices, thus acting as failure agents. Thus, many improvements have been currently developed, such as the use of less hazardous monomers (direct heteroarylation polymerization, DHAP) and less or no transition-metal catalyzed. 19

Future. Today we have entered a new era where π-conjugated polymers could be made from biosourced monomers, the so-called biomass. [START_REF] Gomez | Upgrading the Chemistry of π-Conjugated Polymers toward More Sustainable Materials[END_REF] One typical example is the lignocellulose whose production cycle is rather short (1-50 years). Most importantly, the lignocellulose can be used for energy production without competing with food production. Furthermore, the lignocellulose is also a good candidate to provide a large palette of molecules. For example, cellulose, the most abundant biopolymer in nature, has a crystalline structure and consists of cellobiose repeating units. Cellulose can be applied in optoelectronic devices [START_REF] Karakawa | Organic Light-Emitting Diode Application of Fluorescent Cellulose as a Natural Polymer[END_REF] . In addition to the lignocellulose, multiple biomasses with their characteristics exist in nature, demonstrating that biomass is a promising alternative to petroleum resources.

Design principles

To design conjugated polymers for optoelectrical applications, several general principles should be kept in mind, including (1) side chains to enhance the solubility and processability, (2) high molecular weights, (3) bandgap and absorption behavior, (4) HOMO and LUMO energy levels, and ( 5) suitable morphology with low barriers. These factors are dependent on each other and must be comprehensively considered for specific target properties.

For instance, side chains play a significant role in improving the solubility and the obtainable molecular weight of conjugated polymers, but also influence their intermolecular interactions through changes in morphology and thereby the charge carrier mobility. Tuning the energy bandgap for obtaining the desired absorptions will usually change the HOMO and LUMO energy levels, and thus change the emitting color in an organic light-emitting diode (OLED) or influence the open-circuit voltage (Voc) in a polymeric solar cell. Therefore, it is necessary to fully account for these designing principles and balance the guiding concepts in pursuit of ideal polymers for specific applications.

Polymer backbone

Most optoelectronic properties of conjugated polymers stem from the attributes of the conjugated backbone, making the polymer backbone design one of the most important aspects to consider when creating new materials tailored to a specific organic electronic application. The primary handles a synthetic chemist can control, in conjugated polymer backbones, include conjugation length, inter-ring torsion or dihedral angles, the electron density of the monomers, and the interplay between electronrich and electron-poor comonomers in donor-acceptor architectures.

Conjugation length. We already introduced the concept that increasing the number of overlapping 2pz orbitals leads to a decrease in Eg until the effects of BLA limit any further reduction. However, for many conjugated polymeric systems, the bandgap and other electronic properties can be limited by the effective conjugation length of the backbone. The effective conjugation length can be thought of as the minimum number of monomer units necessary to saturate the optoelectronic properties of a conjugated polymer.

Bredas's team figured out a linear relationship for Eg and ionization potential (IP) to 1/n, with n corresponding to the number of aromatic rings in a chain. [START_REF] Bredas | Chain-Length Dependence of Electronic and Electrochemical Properties of Conjugated Systems: Polyacetylene, Polyphenylene, Polythiophene, and Polypyrrole[END_REF] This means that increasing chain length will decrease the bandgap and increase the λmax of the polymer absorption. The change would diminish as the chain size increases, effectively reaching a plateau.

As an example, Miller and coworkers experimentally observed this trend using well-defined oligomers of 9,9-di-n-hexylfluorenes (n = 3-10). The absorption profile, shown in Figure 1. 4, continuously redshifted with increasing chain length, but by 10 units the λmax already were close to the level of poly (9,9-din-hexylfluorene) with an average length of 54 fluorene units. Using the linear extrapolation of 1/n to 1/λmax, the authors determined the effective conjugation length of the polymer to be around 12 fluorene units or 24 aromatic rings. [START_REF] Klaerner | Polyfluorene Derivatives: Effective Conjugation Lengths from Well-Defined Oligomers[END_REF] Using the same method, the effective conjugation length of polyacetylene and polythiophene can be estimated to be around 30 double bonds [START_REF] Schaffer | Linear Optical Properties of a Series of Polyacetylene Oligomers BT -Conjugated Polymeric Materials: Opportunities in Electronics, Optoelectronics, and Molecular Electronics[END_REF] and 20 rings [START_REF] Meier | Effective Conjugation Length and UV/Vis Spectra of Oligomers[END_REF] , respectively. The differences in effective conjugation length probably result from the presence of inter-ring torsion, of dihedral angles between aromatic monomer units, hindering the ability for a conjugated polymer to achieve periodicity in its conjugation. Heteroatom exchange in conjugated scaffolds (atom engineering). Salzner's group investigated the relationship between the geometries and electronic structures of various heterocyclic organic polymers using the fragment molecular orbital method (FMO), and concluded that the bandgap increase with increasing π-donor strength of the heteroatom, as depicted in Figure 1. 5. 11 Consequently, heteroatom exchange can greatly affect the electronic structures, optical and electronic properties, and charge carrier mobility. [START_REF] Ashraf | Chalcogenophene Comonomer Comparison in Small Bandgap Diketopyrrolopyrrole-Based Conjugated Polymers for High-Performing Field-Effect Transistors and Organic Solar Cells[END_REF] The most commonly used heteroatoms in conjugated molecules are sulfur (S), oxygen (O), and nitrogen (N) to bridge the carbon scaffold. Main-group elements, including silicon (Si), phosphorus (P), boron (B), selenium (Se), and tellurium (Te), are also replaced to achieve expected electronic properties. For example, Se and Te have been incorporated into S-containing donor-acceptor conjugated polymers to decrease the bandgap and improve hole mobility. 26 polyisothianaphthene (PITN), with a benzene ring fused on 3,4-positions of thiophene unit of polythiophene, favors the quinoid form to retain the aromaticity of benzene, because benzene has higher aromatic resonance energy of benzene (1.56 eV), compared to that of thiophene (1.26 eV). [START_REF] Hoogmartens | Low-Bandgap Conjugated Polymers. A Joint Experimental and Theoretical Study of the Structure of Polyisothianaphthene[END_REF] Hence, the fused-ring structure is a good choice for conjugated molecules to achieve a low bandgap.

Torsion. Torsion between aromatic rings has been proved to greatly affect the conformational and optoelectronic properties of conjugated polymers, by studying the influence of the regioregularity of alkyl substituents on the poly (3-alkylthiophene) properties and coming to the conclusion that the headto-head sequences produce a steric hindrance, reduce the π-conjugation and further increase the bandgap). 28 Aside from regioregularity, torsion can also be manipulated by controlling the number and sorts of the substituted side chains, through the steric interactions between side chains in whether homopolymers or copolymers. Moreover, torsion can be created from electronic effects through heteroatom interactions. For example, in PEDOT, as shown in Figure 1. 8, the interactions between the sulfur atoms (S) in the thiophene backbone and the oxygen atoms (O) of the dioxyethylene bridge effectively locks the backbone into coplanarity. [START_REF] Spencer | The First Direct Experimental Comparison between the Hugely Contrasting Properties of PEDOT and the All-Sulfur Analogue PEDTT by Analogy with Well-Defined EDTT-EDOT Copolymers[END_REF] The high degree of coplanarity facilitates π-π interactions, enable a higher degree of electron donation into the backbone from donating substituents, and increase the delocalization of charge across donor-acceptor copolymers.

Electron density. The extent to which monomers in the polymer backbone are electron-rich or electron-poor plays a pivotal role in the electronics of conjugated polymer systems. Electron-rich monomers are more easily oxidized, contributing to a lower oxidation potential Eox of the resulting polymer. Lowering this Eox can also be thought of as raising the HOMO level of the polymer, and therefore incorporation of electron-poor monomers serves to deepen the HOMO level. Since energy levels play an important role within organic electronic applications, allowing the polymer to inject or receive electrons from adjacent materials, the electron density of the monomers that make up a conjugated polymer is another approachable handle for organic chemists when designing new materials tailored for a specific application. Aside from the aromatic unit of the conjugated backbone, side-chain substituents can also be chosen for their ability to donate or withdraw electrons from the backbone as a handle over energy levels. Donor-acceptor copolymers. Another significant approach to tuning bandgap within conjugated polymers is the use of a donor-acceptor or push-pull architecture along with the backbone. Proposed by Havinga et al. and visualized in Figure 1. 8, the donor-acceptor approach makes use of the orbital mixing between covalently connected electron-rich (donor) and electron-poor (acceptor) monomers to lower bandgap in the resulting conjugated copolymers and push absorption out to the near-IR. [START_REF] Havinga | Alternate Donor-Acceptor Small-Band-Gap Semiconducting Polymers; Polysquaraines and Polycroconaines[END_REF] The built-in dipole created from the donor to the acceptor aids in the delocalization of electron density in the backbone, which has made these systems popular for bulk heterojunction (BHJ) OPV active layers in which the polymer is excited by ambient light and the resulting electron can be shuttled from the donor moiety to the acceptor moiety, and finally transferred to the LUMO of the acceptor (e.g. fullerene) in the blend.

Side chain

As previously introduced, the incorporation of side chains onto conjugated polymer backbones has vastly expanded the field by allowing for new structures to be synthesized through solution-based polymerizations, characterized through standardized methods, and processed via solution-based methods. However, solubility is just one of the many merits obtained through the incorporation of side chains. In the following section, we will explore how side chains can be used to modify solubility, solid-state morphology and microstructure, material functionality, and the interplay that exists between these properties.

Solubility.

Good solubility is one of the most straightforward properties achieved through side chains.

To gain good solubility in common organic solvents, both linear and branched aliphatic side chains are the most commonly used. For n-alkyl chains, the solubility of polymers increases along with longer chains, as more rotational degrees of freedom are added to the structure. Branched alkyl chains are also beneficial for enhancing solubility without the need to increase the chain length, as the branching disrupts side-chain interdigitation and also creates a chiral center, both leading to a more disordered, and more soluble, structure.

The aliphatic chains can further be modified by the replacement of heteroatoms, such as oxygen (O), to form oligoether, or terminated with ionic groups to form polyelectrolytes [START_REF] Elbing | In Situ Conjugated Polyelectrolyte Formation[END_REF] , leading to better solubility in polar solvents. These side-chain motifs are shown below in Figure 1. 9. In all of these examples, it must be noted that side chains are not simply supplemental pieces of the conjugated polymer that can not only be used for solubility purposes, but will have an impact on the polymer's structure and materials properties. As the field moved towards branched aliphatic side chains in efforts to further increase solubility, it became apparent that there was a complex relationship between solubility and solid-state structure.

Replacing linear side chains with branched alternatives disrupts the ability to interdigitate, and while this greatly increases the solubility of the polymer, it also prevents the formation of ordered domains in the solid-state.

A recent example in the Reynolds group shows an isoindigo-terthiophene polymer that achieves ~5.1% in OPV devices when using linear hexyl chains, but drops to ~0.3% when using 2-ethylhexyl branched chains due to the total disruption of solid-state order. [START_REF] Grand | Morphology Control in Films of Isoindigo Polymers by Side-Chain and Molecular Weight Effects[END_REF] Despite the tendency to disrupt order, branched side chains are still ubiquitous in modern conjugated polymer design due to their ability to solubilize flat, conjugated molecular units, and work from the OFET community has revealed that their effect on solid-state packing can be minimized by pushing the branching point further away from the conjugated backbone. [START_REF] Lei | Influence of Alkyl Chain Branching Positions on the Hole Mobilities of Polymer Thin-Film Transistors[END_REF] The difficulty with side chains is that their effects, beyond solubility, can be difficult to predict and are often dependent on both repeat unit structure and intended application. Copolymers containing three or four side-chain sites per repeat unit are now commonplace, and each site adds another variable to contribute to the overall complexity. A notable example of the complex nature of side-chain effects is the hypothesis put forward by Graham et al. that in donor-acceptor copolymers for use in PCBM blend OPVs, having bulky side chains on the donor moiety and linear chains on the acceptor moiety yields the optimum device metrics. [START_REF] Graham | Importance of the Donor:Fullerene Intermolecular Arrangement for High-Efficiency Organic Photovoltaics[END_REF] The idea is that the bulky side chains direct PCBM molecules towards the less sterically hindered acceptor moiety, thereby improving electronic interactions and facilitating charge transfer. While this hypothesis is appliable for a handful of systems, there are certainly outliers, and there is probably no universal theory for predicting how side chains will impact a conjugated polymer backbone in the solid-state. Therefore, it is important for polymer chemists to perform side chain optimization studies on new conjugated backbones and observe the effects on the solid-state structure through X-ray scattering techniques like GIWAXS, GISAXS, and RSOXS. While many structure-property relationships can be hypothesized, new materials will emerge in direct conflict with those relations, and ultimately much of the field is still in a state of trial and error when it comes to side chains.

Aside from morphology, side chains can also affect the optoelectronic properties by donating or withdrawing electron density and altering inter-ring torsion angles. An interesting example from Guo et al. shows large changes in a series of naphthalene diimide (NDI) bithiophene copolymers by varying the side chains on the bithiophene. [START_REF] Guo | Conjugated Polymers from Naphthalene Bisimide[END_REF] Because the side chains are arranged in a head-to-head position, bulky branched chains create significant torsion between the thiophene units and render the polymer amorphous in the solid-state. When moving to linear chains, the torsion is decreased, leading to an increase in effective conjugation length observed by a red-shift (~38 nm) of the thin film's maximum absorption. Finally, using linear alkoxy chains leads to interactions between the oxygen on the side chain and sulfur on the thiophene backbone, causing an increase in planarity and also an increase in electron density due to the alkoxy donation. The combined effects red-shift thin film absorption max by ~278 nm relative to the branched side chain derivative. In this manner, side chains have been widely used to modify planarity and electron density to control both the absorption profile and electronic bandgap.

Functional and reactive side chains. Side chains containing reactive and functional components have been used to append additional functionality into conjugated polymer designs. The first functionality is solubility modifiers: as mentioned above, according to the required solubility, different types of side chains, including linear/branched alkyl chain, ester alkyl chain, or polyelectrolytes can be designed and obtained. The second functionality is to form chemical or physical crosslinking. When the side chains are terminated with azide groups, chemical crosslinking can be reached by "click chemistry".

When the side chains are substituted by nitrogen (N), oxygen (O), fluorine (F), or ionic groups, physical crosslinking is formed by secondary reversible interactions such as hydrogen bonds and ionion interactions. The third functionality is side-chain cleavage, providing the ability to make use of side chains for the solubilizing properties, but then removing them in the solid-state to increase the density of conjugated backbone within thin films. For instance, silyl side chains that can be cleaved with strong acids, and o-nitrobenzyl units that can be cleaved via UV light and offer the ability to photopattern conjugated polymers. [START_REF] Smith | Thiophene-Based Conjugated Polymers with Photolabile Solubilizing Side Chains[END_REF][START_REF] Jakob | Synthesis of Polyphenylenes from a Soluble Precursor: The "Shaving" Approach[END_REF] These examples demonstrate the potential for side chains to impact more than just solubility, and over the last decade, researchers are just beginning to scratch the surface of the possibilities that exist within functional side chains.

Polymer synthesis

As π-conjugated polymers as semiconducting materials have attracted broad academic and industrial interest for a wide range of applications, this means such tailor-made conjugated materials have first to be designed and prepared. But as said before, the critical aspect of conjugated polymers lies in their preparation as their optical and electronic properties are intrinsically linked to their extended conjugation pathway. Robust, reproducible, and reliable polymerization methods are therefore of utmost importance. In particular, to obtain high molecular weight polymers with extended πconjugation, multiple C-C bond couplings between two sp 2 or sp hybridized carbon atoms are necessary.

Thus, in this part, we first review a few initial synthetic strategies but focus as well on more recent alternative routes to π-conjugated backbone: we will particularly put emphasis on Suzuki crosscoupling, Stille cross-coupling, and the GRIM polymerization technique, as we will eventually use these chemical tools to prepare our target materials. And new greener methods will also be discussed.

Finally, we will briefly introduce the general approaches to the incorporation of side groups onto the polymeric backbones.

Backbone synthesis

Traditional methods. Initial synthetic methods for conjugated polymers included the Ziegler-Natta polymerization of acetylene [START_REF] Ito | Simultaneous Polymerization and Formation of Polyacetylene Film on the Surface of Concentrated Soluble Ziegler-Type Catalyst Solution[END_REF] and oxidative polymerization of poly(phenylene)s, poly(thiophene)s, poly(pyrrole)s, and poly(aniline)s. [START_REF] Sadki | The Mechanisms of Pyrrole Electropolymerization[END_REF][START_REF] Toshima | Direct Synthesis of Conducting Polymers from Simple Monomers[END_REF][START_REF] Roncali | Conjugated Poly(Thiophenes): Synthesis, Functionalization, and Applications[END_REF][START_REF] Waltman | Electrically Conducting Polymers: A Review of the Electropolymerization Reaction, of the Effects of Chemical Structure on Polymer Film Properties, and of Applications towards Technology[END_REF] Following these early methods, synthesis of poly(hetero-arene)s has increasingly relied on transition metal-catalyzed cross-couplings [START_REF] Xu | Pd-and Ni-Catalyzed Cross-Coupling Reactions in the Synthesis of Organic Electronic Materials[END_REF] such as Heck, Kumada, Negishi, Suzuki, Stille, and Sonogashira polycondensations (Figure 1. 11).

We should mention the importance of these Pd-catalyzed cross-coupling reactions for the formation of a C-C single bond allowing the polymerization of conjugated units. Professors R. F. Heck, E.i. Negishi, and A. Suzuki shared the 2010 Nobel Prize in Chemistry for the development of those synthetic tools. [START_REF] Carsten | Polycondensation for Synthesis of Functional Materials[END_REF][START_REF] Bao | Synthesis of Conjugated Polymer by the Stille Coupling Reaction[END_REF][START_REF] Suzuki | Cross-Coupling Reactions Of Organoboranes: An Easy Way To Construct C C Bonds (Nobel Lecture)[END_REF] Indeed, they helped a lot in the design of stable semiconducting polymers with tunable electronic and optical properties. In the following, Stille coupling and Suzuki cross-coupling reactions will be introduced in detail, as we chose these methods to synthesize the polymers described in chapter 2 and 3, respectively. coupling reaction between organostannanes and halides or pseudohalides, with very few limitations on the R 2 -groups. Well-elaborated methods allow the preparation of different products from all of the combinations of halides and stannanes. The main drawback is the toxicity of the tin compounds used, and their low polarity, leading to poor solubility in water. The mechanism of the Stille reaction [START_REF] Carsten | Polycondensation for Synthesis of Functional Materials[END_REF] has been extensively studied. As represented in Figure 1. 12, the catalytic cycle is composed of three steps: the first step is the oxidation addition of a halide or pseudohalide (R 1 -X) to a Pd(0) catalyst to form Pd(II); Next is the transmetalation of Pd(II) with an organostannanes 4; the third step is the reductive elimination of 5 to yield the coupled product (R 1 -R 2 ) and the regenerated Pd(0) catalyst. The Stille coupling has been developed to achieve alternating conjugated polymers, which have potential applications in displaying technologies such as organic thin-film transistors (OTFTs), organic lightemitting diodes (OLEDs), and organic photovoltaics (OPVs). The reaction is suitable for aryl and alkenyl halides and aryl and alkenyl borane compounds. The advantages of Suzuki coupling over other similar reactions include the availability of common boronic acids, mild reaction conditions, and its less toxic nature. The mechanism of the Suzuki crosscoupling [START_REF] Matos | Alkylboranes in the Suzuki-Miyaura Coupling: Stereochemical and Mechanistic Studies[END_REF][START_REF] Smith | Mechanistic Studies of the Suzuki Cross-Coupling Reaction[END_REF] is analogous to the catalytic cycle for the Stille reactions and has four distinct steps (Scheme 1. 4). The initial step is the oxidative addition of an organic halide to the Pd(0)-species to form Pd(II). Next is the exchange of the anion attached to the palladium for the anion of the base (metathesis). The third step is the transmetallation between Pd(II) and the alkylborate complex.

Although organoboronic acids do not transmetallate to the Pd(II)-complexes, the corresponding atecomplexes readily undergo transmetallation. The quaternization of the boron atom with an anion increases the nucleophilicity of the alkyl group and it accelerates its transfer to the palladium in the transmetallation step. The final step is the reductive elimination to form the C-C sigma bond and generate Pd(0). Very bulky and electron-rich ligands (e. In some specific cases, dehalogenation [START_REF] Spivey | Axially Chiral Analogues of 4-(Dimethylamino)Pyridine: Novel Catalysts for Nonenzymatic Enantioselective Acylations[END_REF] , β-hydride elimination [START_REF] Miyaura | Novel and Convenient Method for the Stereo-and Regiospecific Synthesis of Conjugated Alkadienes and Alkenynes via the Palladium-Catalyzed Cross-Coupling Reaction of 1-Alkenylboranes with Bromoalkenes and Bromoalkynes[END_REF] ; and cleavage of some functional groups (e.g., amino group [START_REF] Doubina | Effect of Initiators on the Kumada Catalyst-Transfer Polycondensation Reaction[END_REF] ) are also possible. In order to reveal the full scope of Suzuki polycondensation for the synthesis of high molar mass conjugated polymers, the reaction conditions must be optimized in terms of choice of monomers, catalyst, and solvent, based on careful consideration of the mechanism of the reaction. While much progress has been made, there still remains much scope to further improve these reactions.

The polymers prepared by Stille or Suzuki polycondensation often contain significant traces of the Pd catalysts. These have been proved to have adverse effects on the conjugated polymers' performance in transistors and in solar cells. The levels can be reduced by appropriate treatment, but total removal may be difficult without damaging the polymer. This is a problem with all metal-catalyzed polymerizations.

Towards regioregular polymers. In parallel, and following the first studies on poly(3alkylthiophene)s, it became quite clear that the synthesis of well-defined head-to-tail coupled (which should yield the lowest steric hindrance from the side chains and possibly a more efficient threedimensional packing) poly (3-alkylthiophene)s would lead to a significant improvement in the performance of these polymeric materials. [START_REF] Leclerc | Structural Analysis of Poly(3-Alkylthiophene)S. Die[END_REF] Therefore, in an attempt to bring more reliable synthetic procedures towards the field of electronic materials, a variety of synthetic strategies were utilized and allowed significant advances in this research field.

McCullough [START_REF] Mccullough | Enhanced Electrical Conductivity in Regioselectively Synthesized Poly(3-Alkylthiophenes)[END_REF] and Rieke 55 independently reported the first preparations of well-defined regioregular poly(3-alkylthiophene)s by metal-catalyzed polymerization (Scheme 1. 5). These relatively complicated polymerization procedures have been optimized and simplified by McCullough's team, leading to the Grignard metathesis (GRIM) method. [START_REF] Loewe | A Simple Method to Prepare Head-to-Tail Coupled, Regioregular Poly(3-Alkylthiophenes) Using Grignard Metathesis[END_REF] As we would take advantage of GRIM polymerization method to obtain the polymers developed in chapter 2, below we detail a little more this polymerization method. Scheme 1. 5 Synthesis of processable regioregular poly(3-alkylthiophene)s.

Grignard metathesis (GRIM).

In contrast to the other described methods, GRIM method does not require low temperature conditions, making the process easier and faster. The mechanism (Scheme 1. [START_REF] Iovu | Experimental Evidence for the Quasi-"Living" Nature of the Grignard Metathesis Method for the Synthesis of Regioregular Poly(3-Alkylthiophenes)[END_REF] consists of three consecutive steps: In the first step, 2,5-dibromo-3alkylthiophene is treated with one Grignard reagent (RMgX) equivalent. Two species are formed: compounds 1 and 1' in the proportions ~85% and ~15%, respectively. Due to the steric effect, only the monomer 1' can react with the catalyst. Polymerization starts when the catalyst Ni(dppp)Cl2 is added.

6) proposed by McCullough

The head-tail coupling rate is more than 99%, the yield is about 70% and with an Ip around 1. For instance, this existing polymerization method eliminates the need for highly reactive metals and can even lead to well-defined block copolymers. Moreover, among all poly(3-alkylthiophene)s investigated, regioregular poly(3-hexylthiophene) (rr-P3HT) has shown the best electronic properties together with adequate processability. Both rr-P3HT and PEDOT are currently the most utilized conjugated polymers and are commercially available from various commercial sources.

However, all these state-of-the-art methods generally involve numerous synthetic steps and organometallic reagents that give rise to metal waste and various by-products. Low cost, environmentally friendly, and more efficient synthetic procedures would therefore be a great asset to the sustainable preparation of affordable and efficient conjugated polymers.

Towards greener and cheaper polymerization methods. As mentioned above, simple, reproducible, environmentally benign, and low-cost polymerization methods can be seen as the Holy-Grail for organic electronics. That's why the development of novel polymerization methods for producing conjugated materials is an ongoing topic. Indeed, conventional (hetero)aryl-(hetero)aryl cross-coupling reactions for C-C bond formation after Suzuki, Stille, Negishi, or Kumada are of highest relevance in organic and macromolecular chemistry.

One obvious disadvantage of these reactions is, however, the utilization of various organometallic reagents (or related anion equivalents) that produces stoichiometric amounts of by-products during coupling. These reagents and the resulting by-products are often toxic or environmentally risky, especially in the case of stannyl derivatives. In addition, synthesis of these organometallic monomers often requires multistep procedures as well as expensive purification steps. To overcome these shortcomings, much efforts has been made and direct hetero arylation polymerization (DHAP) appeared as one new technique involving less hazardous chemicals during the process.

Direct hetero arylation polymerization (DHAP).

DHAP is a metal-catalyzed coupling reaction between an arene and an aryl halide that enables the synthesis of π-conjugated polymers while generating fewer wastes and using 'simpler' and less hazardous monomers (Scheme 1. 7).

Scheme 1. 7 Schematic representative of DHAP.

DHAP possesses multiple advantages, among which, the main one is that the monomers, arene and aryl halide, are easily accessible and can bear various substituents. Compared to Stille or Suzuki couplings, DHAP needs less synthetic steps and produces less harmful wastes. And DHAP is likely to synthesized polymers with similar or even better properties than those synthesized with Stille or Suzuki couplings. [START_REF] Kuwabara | Direct Arylation Polycondensation: A Promising Method for the Synthesis of Highly Pure, High-Molecular-Weight Conjugated Polymers Needed for Improving the Performance of Organic Photovoltaics[END_REF] However, limited by the mechanism, DHAP also suffers from the metal catalysts used. Moreover, DHAP are lack of regioselectivity, leading to branching reactions such as homocoupling. These two problems can be avoided by choosing suitable experimental conditions (catalyst and solvent) and also blocking other positions. As an example, Ozawa's team successfully obtained P3HT with high molecular weight (Mn = 31 kDa, Mw/Mn = 1.60) and high regioregularity (98%) comparable to those obtained using either McCullough, Rieke or GRIM methods (Scheme 1. 8). [START_REF] Wang | Palladium-Catalyzed Dehydrohalogenative Polycondensation of 2-Bromo-3-Hexylthiophene: An Efficient Approach to Head-to-Tail Poly(3-Hexylthiophene)[END_REF] To sum up, DHAP has imposed itself as an attractive method to procure well-defined and high molecular weight conjugated polymers. Scheme 1. 8 Poly(3-hexylthiophene) obtained by DHAP.

One step further: transition-metal free synthesis. While organic electronics are ubiquitous in our daily lives, studies dealing with their environmental impact or their sustainability are scarce. As mentioned above, all transition-metal catalyzed cross-coupling reactions suffer from the catalytic system used. The hazardous impurities formed during the coupling reaction remains and acts as charge traps in the final polymers, affecting their properties. Therefore, new trials are made to prepare πconjugated polymers via transition-metal free syntheses. [START_REF] Gomez | Upgrading the Chemistry of π-Conjugated Polymers toward More Sustainable Materials[END_REF] Up to now, it has been proved that πconjugated polymers can be synthesized with halogen, such as bromine-catalyzed reaction 59 (Scheme 1. 9) and oxidative homocoupling of bis-Grignard reagents in nitroxide-mediated radical polymerization (NMRP) approach 60 (Scheme 1. 10). Scheme 1. 9 Synthesis of PEDOT (left) and PEDOS (right) derivatives. [START_REF] Patra | Metal Free Conducting PEDOS, PEDOT, and Their Analogues via an Unusual Bromine-Catalyzed Polymerization[END_REF] Scheme 1. 10 Synthesis of polyfluorene by oxidative homo-coupling of Grignard reagents. [START_REF] Maji | Transition-Metal-Free Synthesis of Conjugated Polymers from Bis-Grignard Reagents by Using TEMPO as Oxidant[END_REF] However, Kanbara's group investigated the role of terminal halogen atoms on the polymers' properties and concluded that the presence of terminal bromide had a bigger impact on the opto-electronic properties than residual palladium. [START_REF] Kuwabara | Effects of the Terminal Structure, Purity, and Molecular Weight of an Amorphous Conjugated Polymer on Its Photovoltaic Characteristics[END_REF] Therefore, it is crucial to limiting the use of not only transition metals but also halogens so that to avoid not only long and tedious purification but also additional steps to remove the final halogen and improve the polymers' properties. Some condensation reactions with neither halogen atoms nor transition metals are exemplified as well, involving the synthesis of polyazomethines [START_REF] Barik | A Fluorescent All-Fluorene Polyazomethine-towards Soluble Conjugated Polymers Exhibiting High Fluorescence and Electrochromic Properties[END_REF] , Knoevenagel reaction [START_REF] Greenham | Efficient Light-Emitting Diodes Based on Polymers with High Electron Affinities[END_REF] and condensation of squaric acid [START_REF] Zhou | Surface Modification of Polysquaraines to Sense Humidity within a Second for Breath Monitoring[END_REF] and Aldol condensation.

Horner-Wadsworth-Emmons (HWE) reaction is also an efficient alternative to the Wittig reaction and enables well-controlled polymerization of various polymers. For example, Scheme 1. 11 illustrates the synthesis of a thiophene-based π-conjugated polymer via the HWE reaction. [START_REF] Goto | Transition-Metal-Free and Halogen-Free Controlled Synthesis of Poly(3-Alkylthienylene Vinylene) via the Horner-Wadsworth-Emmons Condensation Reaction[END_REF] Scheme 1. 11 Synthesis of a thiophene-based π-conjugated polymer via the HWE reaction. [START_REF] Goto | Transition-Metal-Free and Halogen-Free Controlled Synthesis of Poly(3-Alkylthienylene Vinylene) via the Horner-Wadsworth-Emmons Condensation Reaction[END_REF] More interestingly, Zhang's team firstly investigated the synthesis of an isoindigo-based polymer using aldol condensation, 66 as presented in Scheme 1. 12. Scheme 1. 12 Aldol condensation of an isoindigo-based polymer. [START_REF] Zhang | Facile Green Synthesis of Isoindigo-Based Conjugated Polymers Using Aldol Polycondensation[END_REF] In addition to the above-mentioned alternative coupling reactions with or without halogen, it is also possible to perform polymerization via electro-polymerization or vapor phase deposition of appropriate monomers, in order to avoid the use of transition-metal catalysts. But the resulting polymers can't achieve well-defined π-conjugated structures.

Finally, we won't discuss it into details here but a new way of designing of π-conjugated polymers using biomasses is currently explored. As examples, we can cite bio-based substrates having good potential in the field of organic electronics, i.e. cellulose and its derivatives. Indeed, cellulose was used recently as a promising monomer for the synthesis of various polymers and is also a promising building block for organic electronics. [START_REF] Karakawa | Organic Light-Emitting Diode Application of Fluorescent Cellulose as a Natural Polymer[END_REF] To sum up, while efforts have been made in parallel to design bio-based π-conjugated polymers or to develop alternative environment-friendly routes to semiconducting polymers, there is a great deal of room for development and progress in combining these two methodologies targeting more sustainable yet still efficient materials for organic electronics. It is obvious and promising that lignocellulosic biomass can be a source of a wide platform of substrates with various structures (aromatic, heterocyclic, linear, etc.) and functionalities (aldehyde, hydroxy, and methoxy for example).

Incorporation of side chains

As mentioned above, the incorporation of side chains onto conjugated backbones has afforded conjugated polymers better solubilities and processabilities. Commonly there are two approaches to grafting side chains: post-functionalization and pre-functionalization.

Post-functionalization.

Post-functionalization involves two steps: the first step is that the polymer backbone terminated with functional groups and side chains terminated with other functional groups are synthesized, respectively. The second step is that the side chains are attached to the backbones through the chemical interaction between these functional groups. The commonly used reaction is the Williamson ether synthesis. The advantage of post-functionalization is that π-conjugated polymeric backbones can be synthesized by avoiding the influences of side chains. The disadvantage is that the substitution may be incomplete due to the steric hindrance and chemical equilibrium. No reaction or side reaction is also likely to occur in some reactive sites. That is to say, it is difficult to gain homopolymer using this strategy. When the backbones are terminated with halide atoms, the remaining halide atoms will have a large impact on the final polymer's optoelectronic properties.

Pre-functionalization.

Pre-functionalization also involves two steps: the first step is that side chains are attached to the monomers via the substitution; the second step is the polymerization of the new monomers. Using pre-functionalization, even though it is sure that every repeating unit is well connected to a side chain, sometimes, the polymerization is not successful because the substitution of side chains may affect the distribution of electrons of the monomers. For example, when thiophene is substituted by a large side group, GRIM method might not be suitable to achieve controlled, high regioregular poly (3-alkylthiophene).

Scope of this thesis

This thesis focuses on the design, synthesis, and characterization of new π-conjugated polymers for organic electronics. More particularly, chapter 2 sets in the continuity of precedent studies of the team regarding the synthesis of a series of macromolecular liquid crystalline π-conjugated architectures specifically designed for OFETs at the Institut Parisien de Chimie Moléculaire (IPCM), in the Equipe de Chimie des Polymères (ECP). Chapter 3 presents the first investigations performed in our lab on new light-emitting polymers developed for third-generation OLEDs, based on thermally activated delayed fluorescence (TADF) materials. Indeed, the group started an activity recently in this field, in the framework of a CNRS-JSPS project between OPERA (Kyushu University, Fukuoka, Japan) and IPCM.

Chapter 2 π-Conjugated polymers for organic field-effect transistors (OFETs)

Electronic devices have witnessed a revolution in recent years, during which they've progressed from traditional Si-based devices to next-generation organic electronic devices.

On the one hand, compared with traditional silicon electronics, devices based on organic field-effect transistors (OFETs) offer unique advantages, including mechanical flexibility, solution processability, and tunable optoelectronic properties. This is why during the past several years impressive advances have been made in conjugated materials-based FETs. In particular, numerous FETs based on highperformance conjugated polymers have been developed thanks to the efforts of material design and device optimization, which provides a promising opportunity for applications in flexible displays, environmental monitoring, electronic skins and wearable devices.

On the other hand, liquid crystalline (LC) materials have large anisotropy of optical, electrical, magnetic, and physical properties because of their self-organized molecular structure and molecular alignment. Moreover, we explained already that charge-carrier transport properties depend not only on the intrinsic electronic properties of the materials, but also on the way the molecules are packed together in bulk. Therefore, one of the key parameters to improve the performance of OFET components is the development of structured and/or more ordered π-conjugated systems. In this context, LC conjugated polymers have recently attracted considerable attention from both fundamental and practical points of view, as various novel physical behaviors have been observed. In addition, these LC materials could be aligned under LC phase and improve consequently the efficiency of various applications such as polarized electroluminescence (EL) devices and organic thin film transistors.

As a consequence, this manuscript chapter 2 starts with an introduction dedicated to bibliography (section 2.1): we will briefly detail the fundamental mechanisms governing OFETs, before to describe different families of liquid crystal materials. Then, we will present a class of organic materials able to give spontaneously self-assembling, i.e. organic liquid crystals, focusing on the π-conjugated systems and especially polymers.

The following two result sections (section 2.2 and 2.3) deal with the design, the synthesis and the characterization of new liquid crystal structured π-conjugated materials for future OFETs applications, looking for potential ambipolar properties. Indeed, only few nano-structure presenting two different electronic properties, such as electron donor and electron acceptor behaviors, have been investigated so far for OFET applications. Thus, after describing the multi-steps chemical strategy optimization, the thermal and self-organization behavior of our novel polymers are investigated. Preliminary charge transport properties are also evaluated in OFET configuration and discussed. More precisely, in section 2.2, we describe the synthesis and the characterization of a supramolecular architecture resulting from the phase separation, at nanoscale level, of two covalently linked πconjugated systems. We report the study of a so-called (Polythiophene-oxa), polymer composed of a regioregular electron-donor poly (3-alkylthiophene) as the backbone and calamitic-type electronacceptor oxadiazole entities as side groups.

In section 2.3, similarly are explored the properties of a so-called (PBTTT-Tri) which consists this time of an extended donor-type backbone, i.e. the poly (2,5-bis(3-alkylthiophen-2-yl)thieno [3,2b]thiophene) (PBTTT), as well as discotic-type triphenylene side groups as acceptor counter-part.

Bibliography

Brief history of OFETs

Since discovered in 1986 [START_REF] Tsumura | Macromolecular Electronic Device: Field-Effect Transistor with a Polythiophene Thin Film[END_REF] , organic field-effect transistors (OFETs) have made exciting progress from a curiosity to a significant research area over the past two decades, and are currently widely applied in many electronic devices, including displays 68 , sensors [START_REF] Stadlober | Transparent Pyroelectric Sensors and Organic Field-Effect Transistors with Fluorinated Polymers: Steps towards Organic Infrared Detectors[END_REF] , radio frequency identification (RFID), and logic elements [START_REF] Baude | Pentacene-Based Radio-Frequency Identification Circuitry[END_REF] .

Why OFETs? OFETs are attractive and widely explored, due to their semiconducting properties on the molecular level, the low thermal budget to construct the devices, the high degree of mechanical flexibility, as well as weak bonding (usually Van der Waals bonds) between organic molecules. [START_REF] Wilke | Organic Field Effect Transistors[END_REF] The weak bonding means that a small energetic input is required for organic semiconductors to selfassemble into favorable configurations on virtually any substrate to achieve some semiconducting properties.

A very brief history of OFETs. In 1986 67 , Tsumura, Koezuka, and Ando fabricated the first OFET device with a recognizable current gain by an in-situ polymerized polythiophene transistor, which is regarded as the most significant milestone for the development of OFETs. This is only in 1998 that a group at the Philips Research Laboratories in Eindhoven succeeded in producing an integrated circuit that consisted entirely of organic materials . [START_REF] Sirringhaus | Device Physics of Solution-Processed Organic Field-Effect Transistors[END_REF] The field-effect charge-carrier mobilities of this first OFETs based solely on organic materials are less than 10 -2 cm 2 •V -1 •s -1 , which was largely inferior to those of inorganic field-effect transistors based on amorphous silicon (a-Si) as a semiconductor (10 -1 cm 2 •V -1 •s -1 ). However, this success opened up completely new areas for application for organic fieldeffect transistors, particularly for developing cheap electronic components.

After much effort, the mobilities of solution-processed OFET components are now approaching those based on amorphous silicon, [START_REF] Koezuka | Field-Effect Transistor with Polythiophene Thin Film[END_REF] owing to the advantage of 'wet chemistry'. More specially, organic semiconductors can be manipulated and processed at much lower temperatures than that required for the processing of a-Si layers in the production of inorganic field-effect transistors. Besides, polymer films, i.e. polyethylene terephthalate (PET), that retain their shape only up to about 180°C are to be used as a substrate for cost-effective and flexible circuits in organic electronics, such as electronic paper.

Nowadays, the individual components in OFETs (electrodes, semiconductors, insulators, possibly encapsulation) can be applied by different techniques: On the one hand, the layers can be deposited from the gas phase in analogy to the processing of most inorganic semiconductors (physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering), whereas on the other hand inexpensive solution techniques (e.g., spin coating, inkjet printing, and screen printing) are possible.

Their use depends on the physical characteristics of the components, such as vapor pressure, stability, and solubility.

In this context, more interested are the materials that can be applied from solution, i.e. solutionprocessable semiconductors, as they should allow large-area processing in roll-to-roll methods, for example, for the electronic control of large active-matrix displays or in electronic labels. Moreover, it is expected that the avoidance of slow and cost-intensive vapor deposition methods in a high vacuum will bring cost advantages. As an example, for use in electronic labels (so-called RFID tags), a production cost of less than one cent per label will be required. [START_REF] Wang | Low-Cost Fabrication of Submicron All Polymer Field Effect Transistors[END_REF] This is the reason why for many complex chemical, physical, and technological questions that involve all OFET components (conductors, semiconductors, and insulators) and their interplay, the organic semiconductor used is always a key component. As a consequence, innovative approaches to the synthesis of organic semiconducting compounds that can be processed from solution and highlight their potential as semiconductors in OFETs. Both low molecular weight compounds ("small molecules" and oligomers) and polymeric semiconductors are suitable for this purpose, whatever they show liquid crystal properties or not.

In this bibliographic section, we focus on this important and rapidly developing field: we start with the basic knowledge on OFETs, before to present the state of the art in terms of high-performance polymers and end with the potential interest of liquid crystal polymers in particular. OFET devices are voltage-controlled three-terminal switching devices, consisting of substrate, organic semiconductor layer, dielectric layer, gate electrode, and source-drain electrode. [START_REF] Zhang | Ambipolar Copolymer of Dithienocoronenedi-Imide and Benzo(Bis)Thiadiazole with Balanced Hole and Electron Mobility[END_REF] As demonstrated in Figure 2.1. 1, there are four main types of OFET structures: bottom-gate top-contact (BGTC), bottomgate bottom-contact (BGBC), top-gate top-contact (TGTC), and top-gate bottom-contact (TGBC).

OFETs construction and functionality

Generally speaking, p-type organic semiconductors prefer bottom-gate OFETs structures, while ambipolar or n-type organic semiconductors favor top-gate OFETs structure, since the gate electrode and the dielectric layer have a certain protective effect on the semiconductor active layer and can prevent air to a certain extent.

When a gate voltage (VG) is applied, free charges are induced at the interface between the semiconductor and dielectric layers. Furthermore, a small source/drain voltage (VSD) forms a current in the channel, because charges are produced due to the electrostatic effect. The induced charge density in the channel is controlled by the value of VG, and the source/drain current (ISD) intensity is also changed during the process. So, VG plays a part in adjusting the current "switches" of a FET.

The parameters of the device are mainly calculated through the output and transfer curves of FETs (scan VSD at a constant VG and scan VG at a constant VSD). [START_REF] Wang | Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer[END_REF] The following parameters are used to evaluate the performance of OFETs. Mobility () reflects the carrier (electron or hole) transfer rate under a certain electric intensity. The physical meaning of threshold voltage (VT) is the minimum VG required to induce the channel. When different VG and VSD are applied, the working modes are different. This value is obtained from a transfer (ISD versus VG) measurement. The current (I)-voltage (V) characteristics (Figure 2.1. 2) in the linear and saturated regimes are readily applicable to both inorganic and organic field-effect transistors:

In the linear regime:

In the saturated regime: Nevertheless, several challenges still exist. Firstly, there is no unified theory for transport mechanism in semiconducting polymers, which needs to be thoroughly studied in the future for understanding the origin of the high performance. Secondly, a practical standard to measure effect without miscalculation has not been employed: indeed, the charge carrier mobility can be determined by various techniques, including time-of-flight (TOF) method, steady-state TF-SCLC method, DI-SCLC method, FET method, and pulse radiolysis time-resolved microwave conductivity (PR-TRMC) technique. [START_REF] Tiwari | Charge Mobility Measurement Techniques in Organic Semiconductors[END_REF] Besides, the device performance is affected by many factors such as molecular packing, interface, and film morphology. More precisely, the charge carrier mobility of organic materials greatly relies on the intrinsic properties of charge carriers, namely, whether they are holes or electrons, molecular structures, and materials morphologies. Apart from that, the aggregation states of materials (such as amorphous and crystalline states) also have a big influence on the charge carrier mobility. As represented in Figure 2.1. 3, the mobility of charge-carrier increases along with increasing the aggregation degree of the organic materials. [START_REF] Tiwari | Charge Mobility Measurement Techniques in Organic Semiconductors[END_REF] Amorphous polymers exhibit the lowest mobility (10 -6 -10 -5 cm 2 •V -1 •s -1 ) as a consequence of a low degree of order. Single crystals possess the highest degree of order, corresponding to the highest mobility (1-20 cm 2 •V -1 •s -1 ), but the processability and film quality have to be improved. Between them, liquid crystalline semiconductors and ordered polymer semiconductors both have efficient mobility (10 -3 -8 cm 2 •V -1 •s -1 ) and good processability for optoelectronic applications.

High-performance conjugated polymers for OFETs

After 30 years of development, much effort has been made to explore the effective material design strategy, the efficient fabrication technology, and the understanding of the relationship between materials and functional devices, to achieve high-performance conjugated polymers for OFET applications. [START_REF] Sirringhaus | 25th Anniversary Article: Organic Field-Effect Transistors: The Path beyond Amorphous Silicon[END_REF] For example, the structures of conjugated polymers have evolved from donor-donor (D-D) to donor-acceptor (D-A) models, and the mobility has increased from the early 10 -5 cm 2 •V -1 •s -1 to much higher values comparable with that of single crystals. [START_REF] Tsumura | Macromolecular Electronic Device: Field-Effect Transistor with a Polythiophene Thin Film[END_REF][START_REF] Venkateshvaran | Approaching Disorder-Free Transport in High-Mobility Conjugated Polymers[END_REF] Conjugated polymers can be classified as hole or electron (p-or n-type) transporting or ambipolar materials according to the type of orderly transferring charge carriers. Although significant progress has been made in the preparation of semiconducting polymers for OFET applications, currently, most high-performance OFETs based on D-A polymers are p-type devices, some of which even show high hole mobilities over 50 cm 2 •V -1 •s -1 with good device stability. [START_REF] Shi | Design and Effective Synthesis Methods for High-Performance Polymer Semiconductors in Organic Field-Effect Transistors[END_REF] In contrast, the development of ambipolar or n-type OFETs falls behind that of p-type devices. [START_REF] Quinn | Recent Progress in the Development of N-Type Organic Semiconductors for Organic Field Effect Transistors[END_REF] Thus, studies on ambipolar or n-type polymers have gained increasing importance in the field of OFETs. [START_REF] Sirringhaus | 25th Anniversary Article: Organic Field-Effect Transistors: The Path beyond Amorphous Silicon[END_REF] Below, we introduce the recent advances in high-performance D-A polymers, including p-type, ambipolar, and n-type counterparts, trying to insist on the key factors explaining their efficiency.

p-type polymers

As mentioned above, the most reported high-performance OFETs based on D-A polymers are p-type devices. Figure 2.1. 4 show the common donor (D) and acceptor (A) used, as well as the structures of some high-performance p-type polymers based on these D and A units. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] The essential criteria for ptype high-performance D-A polymers include:

Appropriate HOMO (-5.0 to -5.5 eV) and LUMO (>-3.5 eV) energy levels. Most p-type D-A polymers hold the highest occupied molecular orbital (HOMO) energy levels in the range of -5.0 to -5.5 eV, which is generally close to the work function (WF = 5.1 eV) of gold electrodes, [START_REF] Guo | Bithiophene-Imide-Based Polymeric Semiconductors for Field-Effect Transistors: Synthesis, Structure-Property Correlations, Charge Carrier Polarity, and Device Stability[END_REF] making it easy for the hole injection from the electrodes into the semiconducting layers.

High molecular weight (Mn). Polymers with high Mn usually show improved crystallinity, better domain connectivity, and reduced grain boundaries, thus enhancing the mobilities. [START_REF] Guo | Imide-and Amide-Functionalized Polymer Semiconductors[END_REF] But it is worth noting that high Mn may also result in reduced solubility, further affecting the fabrication process.

Thus, improving Mn is an effective way to increase mobility when good solubility is ensured. Good backbone conjugation and coplanarity. As charge transport occurs between π orbitals through backbone conjugation in polymeric semiconductors, an enhanced coplanarity will result in more effective backbone conjugation and closer π-π stacking, thus improving the mobilities. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] High crystallinity and uniform film morphology. For OFET devices, the channel length (tens of micrometers) is usually larger than the polymer crystalline domain (tens of nanometers). This means that many grain boundaries exist in the active layer between the source and drain electrodes. These grain boundaries hinder charge transport. Therefore, the polymer film with a high degree of crystallinity and well-connected morphology is favorable for achieving high mobility. Two methods, "side-chain engineering" [START_REF] Mei | Side Chain Engineering in Solution-Processable Conjugated Polymers[END_REF] and "well-aligned film" (by unique device fabrication techniques) 86 are adopted to tune the crystallinity and morphology.

2.1.3.2 Ambipolar or n-type polymers Compared with p-type polymers, so far, most reported ambipolar or n-type polymers are based on strong electron-withdrawing units. [START_REF] Lei | Synthesis, and Structure-Property Relationships of Isoindigo-Based Conjugated Polymers[END_REF] The ideal ambipolar or n-type polymers are basically required to have [START_REF] Zhao | Electron Transporting Semiconducting Polymers in Organic Electronics[END_REF] : Suitable HOMO/LUMO levels relative to the p-type emitter, thereby minimizing the barrier for the electron injection, reducing turn-on/operating voltage, and effectively blocking holes.

High electron mobility ( ) to move the charge recombination zone away from near the cathode and improve the exciton generation rate.

However, low electron mobilities and inferior device stability impede the applications of ambipolar or n-type polymer FETs, because the LUMO energy level of most D-A polymers is between -3.3 and -4.0 eV, which is far from the work function of gold electrodes (WF = 5.1 eV). An effective approach to achieve ambipolar or n-type polymers is to lower their lowest unoccupied molecular orbital (LUMO) energy levels, thus facilitating the electron injection ability and enhance the device stability. Two strategies can be developed to lower the LUMO energy levels: introducing electron-withdrawing groups (EWGs) [START_REF] Lei | Synthesis, and Structure-Property Relationships of Isoindigo-Based Conjugated Polymers[END_REF] (F, N, Cl, etc.) or acceptor dimers ("acceptor dimerization") [START_REF] Guo | Imide-and Amide-Functionalized Polymer Semiconductors[END_REF] into the polymer backbone. In addition to energy level modulation, "side-chain engineering" 85 can also improve the electron mobility of ambipolar or n-type polymers.

* Introducing EWGs (F, N, Cl, CN, and B) into the polymer backbone

Fluorine (F) substitution. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] So far, high electron mobilities of more than 5 cm 2 •V -1 •s -1 have been achieved in some F-containing polymers. Apart from lowering HOMO/LUMO energy levels, incorporating F atoms into a polymer leads to several unique advantages: (1) there is almost no steric hindrance, because F atom shows a small van der Waals radius of 1.35 A°, which is slightly larger than that of H (r = 1.20 Å); (2) it induces intramolecular or intermolecular F-H and F-S interactions, which may enhance the backbone coplanarity and promote better molecular crystallization; (3) it improves the device stability in the air, as the hydrophobicity of F-containing polymers can prevent the diffusion of moisture and oxygen into the films. Despite these advantages, F-containing polymers usually have poor solubility in common solvents, thus inferior solution-process ability. Moreover, the synthesis of F-substituted units, especially F-containing acceptors and polymers, is quite difficult. Nitrogen (N) substitution. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] N substitution usually refers to the replacement of C-H in an aromatic ring with sp 2 -N. In addition to lowering the HOMO/LUMO energy levels, N-substituted polymers also have similar advantages with F-containing polymers including reduced steric hindrance and possible intramolecular or intermolecular N-H interactions. However, the replacement of C=C with C=N leads to worse π-conjugation, which is harmful to charge transport. Hence, the number and position of substituted N atoms in polymers should be carefully designed, which leads to additional challenges for material synthesis. As a remark, the introduction of N atoms into the acceptors rather than the donors may result as well in higher crystalline microstructure and better electron mobility. Chlorine (Cl) substitution. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] Similar to F substitution, Cl substitution can also lower both the HOMO and LUMO energy levels. As Cl atom has a larger van der Waals radius (1.80 A°) than that of H (r = 1.20 A°), Cl substitution may cause steric hindrance, thus distorting the backbone coplanarity, which is harmful for π-conjugation and intermolecular π-π stacking. To date, only a few chlorinated polymers have been reported. [START_REF] Ryu | Naphthalene Diimide-Based Polymeric Semiconductors. Effect of Chlorine Incorporation and n-Channel Transistors Operating in Water[END_REF][START_REF] Lei | Chlorination as a Useful Method to Modulate Conjugated Polymers: Balanced and Ambient-Stable Ambipolar High-Performance Field-Effect Transistors and Inverters Based on Chlorinated Isoindigo Polymers[END_REF] Figure 2.1. 7 Cl-substituted polymers for ambipolar or n-type OFETs. [START_REF] Ryu | Naphthalene Diimide-Based Polymeric Semiconductors. Effect of Chlorine Incorporation and n-Channel Transistors Operating in Water[END_REF][START_REF] Lei | Chlorination as a Useful Method to Modulate Conjugated Polymers: Balanced and Ambient-Stable Ambipolar High-Performance Field-Effect Transistors and Inverters Based on Chlorinated Isoindigo Polymers[END_REF] Cyano (CN) substitution. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] CN is a strong EWG, which can significantly lower the HOMO and LUMO energy levels. Owing to its bulky size, CN substitution can lead to steric hindrance and further to a twisted backbone, which is harmful for π-conjugation and intermolecular π-π stacking.

Figure 2.1. 8 CN-substituted polymers for ambipolar or n-type OFETs. [START_REF] Kim | Modulation of Majority Charge Carrier from Hole to Electron by Incorporation of Cyano Groups in Diketopyrrolopyrrole-Based Polymers[END_REF][START_REF] Yun | Dramatic Inversion of Charge Polarity in Diketopyrrolopyrrole-Based Organic Field-Effect Transistors via a Simple Nitrile Group Substitution[END_REF] Boron (B) substitution. [START_REF] Yang | Insight into High-Performance Conjugated Polymers for Organic Field-Effect Transistors[END_REF] So far, B-containing ambipolar or n-type polymers for OFETs are scarce, and most reported B-containing polymers have B-N units, which endows the acceptors with fixed planar configuration and low-lying HOMO/LUMO energy. The main challenge of B-containing polymers is also material synthesis. Furthermore, the relationship between material design and device performance is unclear, which needs further research.

* Acceptor dimerization

The second strategy, namely "acceptor dimerization", was recently developed by Liu et al. [START_REF] Yang | Bis-Diketopyrrolopyrrole Moiety as a Promising Building Block to Enable Balanced Ambipolar Polymers for Flexible Transistors[END_REF] This strategy introduces an acceptor dimer with stronger electron-withdrawing property into a polymer and provides a new access for ambipolar or n-type polymers (Figure 2.1. 10). Besides lowering HOMO/LUMO energy levels, this strategy does not cause steric hindrance, maintaining the backbone planarity and the acceptor dimers can be obtained by a general homocoupling reaction. Figure 2.1. 11 displays two reported polymers using the acceptor dimerization strategy, among them, P42 exhibited excellent ambipolar performance with μh and μe values of 6.87 and 8.94 cm 2 V -1 s -1 , respectively. 99

P44-based TGBC OFETs with a CsF electrode-modifying layer showed unipolar n-type performance with a μe of 0.82 cm 2 V -1 s -1 . 100

* Side-chain engineering

In addition to energy level modulation, "side-chain engineering" can also be used to improve the electron mobilities of n-type or ambipolar polymers. Indeed, incorporation of specific side chains into a polymer may result in closer π-π stacking, larger crystalline correlation lengths, and better domain connectivity. Therefore, the modulated polymer can show better intermolecular charge transport and, thus, improved mobilities. We won't detail it in this manuscript but note that fabrication technology is as important as clever material design, as for high-performance OFETs an effective solution-processable technique is the other key factor. Indeed, the solution processability of OFETs lays the foundation for low-cost and large-area flexible electronics. Usually, scientists control the crystallinity of molecules by improving film-forming processes, such as by using high-boiling-point solvents, blends of good and poor solvent, or controlling the physical force effects (shear force, centrifugal force, or capillary force). Irrespective of small molecules or polymers, several solution-processable techniques are commonly used in the laboratory, such as spin-coating, drop-casting, bar coating, solution shearing, and printing.

In this context, liquid crystal (LC) materials could be interesting, as (LCs) are a state of matter exhibiting properties between those of conventional solid and those of isotropic liquid. More specifically, liquid crystals can present dynamic and order properties, leading to large and oriented self-organized domains. This way, the resulting ordered structures on large scale make it possible for liquid crystals to possess a good charge carrier mobility, thus making them potential good candidates in optoelectronic devices and especially for OFETs applications.² We won't detail this research field as we focus our work on polymer materials. But as introduced before already, it must be mentioned that in many cases the authors have not taken advantage of several valuable inherent properties of LC phases, specifically the well-known capability of many LCs to be uniformly "aligned" to improve the device performance, particularly the OSC charge-carrier mobility in thin films. Moreover, the crystallization of liquid crystals at room temperature, generally observed for mesomorphic molecular semiconductors, induces several limitations in the semiconducting layers such as polycrystalline domains, providing a high density of grain boundaries and limited charge mobility. Because of this problem, recent research has focused as well on πconjugated mesogenic polymers.

Semiconducting LC polymers

As explained before, the electronic performance of conjugated polymers depends on the microstructure of the polymer films. We know in particular that, percolated network morphology with high crystallinity, ordered intermolecular packing and long-range order is beneficial for charge transport. In this context, the appearance of liquid crystalline ordering for some conjugated polymers provides a new solution to solve the difficulties in microstructure manipulation.

Importance of the film morphology. The importance of film morphology in electronic performance was already discussed a little claiming the role of the development of bottom-up approaches to regulate it. 117 It was then evidenced that some critical physical parameters, including the lattice constant, 118 crystallinity, 119 and orientational parameters, [START_REF] Tseng | High-Mobility Field-Effect Transistors Fabricated with Macroscopic Aligned Semiconducting Polymers[END_REF] determine the resulting charge mobility of semiconducting polymers in multiscale cases. 120 In fact, during anisotropic charge transport in conjugated polymers, delocalized carriers are transported along and between backbones in ordered regions and hop to adjacent chains in disordered regions at different velocities. 121 The basic rules for tuning microstructures focus on how to reduce the probability of charge transport under unfavorable conditions and improve mobility in certain parts or regions of merit. 122 Improved mobility appears in films with improved crystallinity and sufficient intercrystallite connectivity, and the mobility can be further elevated via alignment techniques to achieve long-range anisotropic charge transport. 123 In addition, driven by π-π interactions, conjugated polymers can assemble into ordered structures in solutions or melts. However, the polymer microstructure is difficult to control because of the relatively weak interaction between conjugation groups and limited molecule mobility. Usually, a semicrystalline structure is attained from a polymer assembly. Thus, various efforts have been made to promote the molecular arrangement process by modulating the driving force for aggregation and improving chain mobility. 124 Unfavorable entropy loss also poses difficulties for polymer long-range alignment, and entanglement and polymer chain relaxation limit the film anisotropy. In other words, a balance between molecular interactions and molecular mobility should be realized to obtain a wellstructured morphology.

This being said, with rigid backbones, highly anisotropic molecular structures, long flexible side chains, and strong π-π interactions between polymers, the chemical structures for most solutionprocessed conjugated polymers exactly meet the chemical structure requirements for liquid crystals.

LC Polymer designs.

The liquid crystalline state of semiconducting polymers was discovered in the 1990s, and the liquid crystallinity of conjugated polymers was applied to assist the construction of field-effect transistors and light-emitting diodes. 125 The liquid crystalline state was first studied for the second generation of conjugated polymers such as poly(phenylenevinylene) (PPV) derivatives, polyacetylene (PA) derivatives, polyfluorene (PF) derivatives, and polyalkylthiophene (PAT)

derivatives. The discovery of liquid crystalline states has not been limited to traditional homopolymers.

Some donor-acceptor (D-A) copolymers with rigid backbones and little crystallinity also exhibit liquid crystal properties. 126 In some reports from the past few years, the liquid crystalline systems were usually associated with a highly crystalline and anisotropic morphology, which appeared both for traditional homopolymers, such as P3HT, and many emerging D-A copolymers, thus stimulating studies on the influence of the liquid crystallinity of conjugated polymers on developing film microstructures. 127 Device performance results have also proved the benefits of liquid crystalline properties in terms of charge transport. 125 dibromo-4,4'-dialkyl-[2,2']-bithiophene. Taking advantage of the lamellar pre-organization in the liquid crystalline state, the charge-carrier mobility of these polymers obtained after annealing in fieldeffect transistor configuration is ranging from 0.2 to 0.7 cm 2 V -1 s -1 .

For this PBTTT material, the delocalization of electrons from the fused aromatic unit into the backbone is less favorable than from a single thiophene ring, due to the larger resonance stabilization energy of the fused ring over the single thiophene ring. This reduced delocalization along the backbone results in a lowering of the polymer's highest occupied molecular orbital (HOMO) level.

Furthermore, the rotational invariance of the linearly symmetrical thieno [3,2-b]thiophene in the backbone facilitates the adoption of the low-energy backbone conformation, promoting the formation of highly ordered crystalline domains. Therefore, PBTTT is more likely to achieve higher mobility than poly(3-alkylthiophene).

These two precedent examples were main-chain LC polymers but side-chain LC polymers exist, Indeed, the introduction of LC side groups grafted on -conjugated backbone is an interesting approach as well, 130 as self-organization adopted by mesogenic side groups can induce an improvement of the polymer chain organization in the same time. As an example, Ben Zhong Tang's group described several π-conjugated side-chain LC polymers. Besides, substituted polythiophenes are comb-like polymers, with both backbone and side-chains independently capable of crystallization. This allows complex behavior from competing processes and polymorphic behavior has been noted. 134,138 DSC data can then be combined with the temperaturedependent X-ray diffraction to study the different mesophases (mesophases transitions). For example, generally, the low-temperature transitions come from the alkyl substitutions (side chains) and hightemperature transitions are designated to "backbones". Some additional transition (glass temperature) can be observed in rrP3AT, transforming a glassy crystal to a plastic crystal with different inter-ring torsion. This was dubbed a twist-glass transition. 140

To sum-up on liquid crystal polymers, they are promising materials, with respect to the formation of uniform films by wet processes and good thermal durability. Moreover, the control of the supramolecular self-assemblies and the nanoscale morphologies of π-conjugated macromolecular architectures with long-range order, as well as the establishment of reliable structure-property relationships can be seen as major and fundamental issues. 141 In particular, better control of both the mesoscopic and nanoscale organization within thin organic semiconducting films is crucial to improve their charge carrier mobilities.

As we described, currently most efforts essentially focus on two different approaches, either based on the elaboration of conjugated block copolymers, (with different block functionalities), 142 or liquidcrystalline -conjugated polymers, bearing conjugated mesogenic side-groups. 143 The first class of materials takes advantage of the block copolymer ability for phase separation into well-ordered morphologies (spherical, cylindrical, or lamellar) to form separate conduction pathways for charge carriers, thanks to the antagonistic chemical nature of each block at the origin of nanosegregation. 144 However, optimal charge transport properties also require to form long-range correlated structures with an orientational control of the regular pathway alternation. This last objective is difficult to achieve by tuning the block structures and length.

On the contrary, it can be more easily envisaged with a liquid-crystalline polymeric architecture.

Liquid crystalline materials are indeed outstanding examples of soft self-assemblies that combine order and fluidity, within components self-organizing into a wide diversity of long-range ordered, periodic structures. 145 In addition, liquid crystal assemblies can form thin films which are intrinsically self-healing since structural defects are automatically corrected during the process of self-assembly, and whose morphology can be controlled at the molecular level.

Objectives: towards new liquid crystal side-chain polymers

In this context, side-chain liquid-crystalline π-conjugated polymers consisting of π-conjugated backbones bearing side-on semiconducting mesogenic groups can be considered as a promising approach to control the phase separation into well-ordered morphologies of different functional components with periodicities ranging in the nanometer scale.

Up to now, only a few examples of such macromolecular architectures have been considered for charge transport properties. 146 Also, associated with electro-active components (donor and acceptor), such well-ordered morphologies could offer the possibility to form separate conduction pathways for charge carriers, by playing on their antagonistic chemical nature. Our research group contributed these last years to this type of polymer architecture. 115,147,[149][150][151][152] More precisely, we designed and synthesized a new kind of side-chain liquid crystal π-conjugated polymers consisting of intricate polymeric systems associating regioregular poly (3-alkylthiophene) backbones with laterally pending π-conjugated mesogenic groups. Depending on the nature of the mesogenic side-groups, this specific polymer design permits to obtain lamello-columnar or lamellolamellar mesophases, resulting in an intertwined co-assembly either of lamellae and columns or of two different types of lamellae, as exemplified in Figure 2.1. 26, with one of our discotic-based triphenylene side-chain homopolymers. 147,148 Associated as well with judicious side-groups, for example, n-type entities, we demonstrated that this simple and versatile strategy can produce distinct conductive channels for both types of charge carriers, and can lead to a new class of supramolecular ambipolar materials, easily processable, and potentially suitable for electronic and optoelectronic applications (see Figure 2.1. 27). Indeed, this homopolymer exhibited ambipolar conduction with an electron mobility of 3.9 x 10 -6 cm 2 •V -1 •s -1 and a hole mobility of 3. For both types of macromolecular architectures, first of all, the multi-steps chemical strategy optimization is described, before to present the chemical structure evidencing by NMR and SEC essentially. Second, the thermal and self-organization behavior of the polymers are further investigated by POM, DSC, and XRD. Third, preliminary charge transport properties of the materials, evaluated in OFET configuration, are discussed. Finally, we will conclude this part with some perspectives based on the new design guidelines providing by this study.

Polythiophene-oxa

In this section, we focus on designing a supramolecular architecture resulting from the phase separation, at the nanoscale level, of two covalently linked π-conjugated systems that enable to selfassemble in a lamella-lamellar nanostructure. To realize our objective, we adopted the strategy that combines a well-defined π-conjugated polymer backbone and π-conjugated mesogenic groups as sidechains to produce a unique semi-conducting liquid crystal macromolecular architecture. More Therefore, first, we will describe the synthesis and structural properties of Polythiophene-Br. Second, we will detail the multi-step synthesis of the functionalized calamitic oxadiazole-type side-group 0F.

Finally, we will present the synthesis and structural properties of target Polythiophene-oxa.

Synthesis of the regioregular precursory Polythiophene-Br

According to the previous work in our team, 3-(ω-bromodecyl)thiophene (1C) can be obtained by lithiation with n-butyllithium of commercially available 3-bromothiophene, followed by quenching with an excess of dibromodecane. Unfortunately, during the lithiation, 2-(ω-bromodecyl)thiophene is also produced as a by-product and consequently, the isomers can only be separated through very complex column chromatography (with hexane or PE as the eluent) as the polarities of the two isomers are very close to each other. Moreover, before this separation is needed a distillation to remove the starting material (3-bromothiophene). Thus, final yields in pure 3 The objective of the first step was to protect only one Br of 1,10-dibromodecane and we managed indeed to obtain the intermediate molecule 1A with a yield of 59%. The second step is a Grignard reaction between the molecule 1A and 3-bromothiophene, which was successful with a relatively good yield as well (58%). Then, the third step is a deprotection reaction to obtain the desired molecule 1C, which was then converted to the monomer 1D through a "classical" bromination experimental procedure, using more specifically NBS.

Then, the precursory regioregular polymer Polythiophen-Br was obtained via GRIM method with Ni(dppp)Cl2 as the catalyst, in a yield of 50%.

Synthesis of 2-(4-decyloxy-phenol)-5-(5-octyl-thiophene-2-yl

)- [1,3,4]

oxadiazole (0F)

As depicted in Scheme 2.2. 3, in order to obtain the side group 2-(4-decyloxy-phenol)-5-(5-octyl-thiophene-2-yl)- [1,3,4]oxadiazole (0F), we first synthesized two building blocks: 5-octyl-thiophene-2carbonylchloride (0C) and 5-(4-methoxy-phenyl)-2-H-tetrazole (0D).

On the one hand, 5-octyl-thiophene-2-carbonylchloride (0C) was obtained from 5-octyl-thiophene-2carboxylic acid (0B) by using thionyl chloride and the conversion was complete. In previous works in our group, the acid group of 0B could be formed starting from n-octyl thiophene, through the intermediate 2-lithio-thiophene generated in-situ and the subsequent addition of carbon dioxide (CO2).

However, in my case, this procedure didn't work. Thus, as illustrated in Scheme 2.2. 3, I decided to first obtain the corresponding aldehyde from the reaction of n-octyl thiophene and POCl3 under 90°C for 2h. Then the aldehyde group (-CHO) of the intermediate 0A was converted into a carboxylic acid (-COOH) group using Jones reagents.

On the other hand, 5-(4-methoxy-phenyl)-2-tetrazole 2-3 was obtained from the reaction between 4methoxybenzonitrile and sodium azide in the presence of ammonium chloride. The product was purified by precipitation and the yield was about 73%.

Scheme 2.2. 3

The synthetic route towards the side group 2-(4-decyloxy-phenol)-5-(5-octylthiophene-2-yl)- [1,3,4] The intermediated product 0E was then obtained through the reaction between 0C and 0D via Nacylation of the tetrazole moiety, in a 74% yield. Finally, the subsequent ether cleavage with BBr3 released the hydroxyl group, and the final side group 2-(4-decyloxy-phenol)-5-(5-octyl-thiophene-2yl)- [1,3,4]oxadiazole (0F) was obtained with a yield of 50%.

Synthesis and structural characterization of target polymer Polythiophene-oxa

As explained in the precedent Scheme 2. After the functionalization, the signal at 3.39 ppm belonging to α-CH2Br of Polythiophene-Br vanished completely and the new signal at 3.94 ppm attributed to the α-CH2O appeared, demonstrating that the substitution is almost 100%. In the meanwhile, the protons of benzene rings exhibited the peaks at 7.96 and 6.94 ppm, the latter peak is overlapped with the signal of polythiophene backbone.

The signals at 7.55 and 6.80 ppm are attributed to the protons of the thiophene rings in the side groups.

Moreover, the signal around 2.82 ppm is ascribed to the α-CH2 peaks of the HT thiophene rings in the backbone and the side groups, and the α-CH2 peak of the TT terminal is around 2.58 ppm. The absolute number of repeating units can also be estimated: Xn,NMR = 3.95 / 0.24 +2 = 18. The broad, overlapping peaks in the range of 0.91-1.75 ppm belong to other alkyl protons.

Size exclusion chromatography (SEC) was also performed to confirm the relative number-average molecular weight (Mn,SEC) and the dispersity (Mw/Mn) of the polymers, using THF as the eluent at In DSC thermograms, an endothermic peak at 132 °C (ΔH = 9.1 J/g) was observed on the DSC trace recorded upon heating, corresponding to the transition from the mesophase to the isotropic phase, which is consistent with the POM observations. On cooling, an exothermic peak was detected at 104 °C (ΔH = 16.1 J/g), attributed to the transition from the isotropic phase to the mesophase. This transition is observed on cooling with a large hysteresis (~30 °C), which is classical for macromolecular systems. In addition, the glass transition was observed at around 50 °C. The result indicated that the as-prepared Polythiophene-oxa transistor exhibits p-type conduction and a hole mobility in the saturated regime was found to be ~ 1.2 x 10 -3 cm 2 V -1 s -1 . The Ion/Ioff ratio was 10 4 and the threshold voltage (Vth) was 30V.

Conclusion

In this section, a new side-chain liquid crystal polymer (Polythiphene-oxa) was synthesized and its structure was characterized by NMR and SEC measurements.

First, we developed an innovative chemical route, even though with more steps, to reach purer bromoalkyl-substituted thiophen monomer leading to an improved method for the preparation of precursor regioregular bromo-alkyl-substituted polythiophene backbone. Then, the final polymer Polythipheneoxa obtained by post-functionalization of the precursor polymer presents a small dispersity and a complete grafting of the side groups.

This material was evidenced to self-organize with an alternation of bilayer of calamitic mesogens side groups and of polythiophene backbone monolayers. A first attempt in device configuration was tested to evaluate its charge transport property, in OFET configuration, and hole conduction with a mobility was about 1.2 x 10 -3 cm 2 V -1 s -1 was measured.

If replacing the side group with the mesogens with stronger electron affinity, it is likely to obtain a material with ambipolar charge transport properties.

PBTTT-Tri

In the last decade, regioregular poly(3-alkylthiophene) has been proved to be a good semiconducting polymer exhibiting high charge carrier mobility for organic electronic applications. In this context, our research team has prepared for ten years a series of liquid crystalline side-chain semiconducting polymers, comprising a regioregular poly(3-alkylthiophene) backbone bearing triphenylene discotic mesogen pendants.

To study the influence of the type of polymeric backbone on the supramolecular self-assembling behavior, and on charge transport properties, in this section, we designed two new side-chain π-

Synthesis and structural characterization

In this part, we also decided to use the post-functionalization method to prepare the target polymers PBTTT-Tri and PBTTT-oxa.

Then, first, we reproduced the synthesis of the monohydroxy triphenylene derivative (Tri), according to an optimized procedure developed precedently in our group. More specifically, we chose the "statistic cyclization" method described by Kong et al 144 This synthetic route for the preparation of the discotic entity (Tri) includes three steps. The two first ones concern the preparation of building blocks B and C obtained by classical Williamson etherification of catechol through adjusting the ratio of bromoalkane. The last step is a ferric chloride oxidatively catalyzed statistic cyclization. The key point in this "statistic" method is to precisely maintain the ratio between B and C as 1:2 to reduce the byproducts (symmetric, dihydroxy, trihydroxy, etc.). The yield of the last step is quite low and the purification of compound (Tri) is tricky due to the presence of the multiple byproducts formed by the statistic cyclization (mainly the symmetric one).

On parallel, we synthesized again 2-(4-decyloxy-phenyl)-5-(5-octyl-thiophene-2-yl)- [1,3,4]oxadiazole (0F) whom chemical route has already been described in section 2.2. This is the reason why we present below only the synthesis and structural characterization of the precursory polymer (PBTTT-Br) as well as the target polymers (PBTTT-Tri and PBTTT-oxa).

Synthesis of precursor PBTTT-Br

Following the literature, the precursor PBTTT-Br was prepared in 6 steps, as shown in scheme 2. Then, the precursor PBTTT-Br was obtained via microwave-assisted Stille polycondensation of the monomers 1G and 2,5-bis(trimethylstannyl)thieno [3,2,b]thiophene. Compared to conventional heating, the use of microwave irradiation has been reported to improve the molecular weight and dispersity, mainly because of the direct transfer of energy of reactants, which significantly reduces reaction time. [START_REF] Carsten | Polycondensation for Synthesis of Functional Materials[END_REF] In my case, after adding all the reactants and degassed, the microwave tube was sealed and heated in the microwave with stirring subsequently at 140 o C for 2 min, at 160 o C for 2 min, and at 180 o C for 25 min. After the precipitation, filtration, and purification with Soxhlet, the precursor PBTTT-Br was obtained with a quite high yield of 90%.

Synthesis of target polymers PBTTT-Tri and PBTTT-oxa

The target polymer PBTTT-Tri was finally prepared via Williamson ether reaction between the precursor PBTTT-Br and 2,3,6,7,10-penta(pentyloxy)-11-hydroxytriphenylene, as depicted in scheme 2.3.3. After precipitation, filtration, and purification by Soxhlet to remove any trace of residual Tri and non-grafted polymer, pure target polymer PBTTT-Tri was gained with a yield of 80%. As PBTTT-Br and PBTTT-Tri have several possible end groups, we can't obtain the absolute number of the repeating units (Xn) using the same method in the cases of Polythiophene-Br and Polythiophene-oxa. Apart from NMR measurements, SEC was conducted to characterize the relative number-average molecular weight (Mn) and the dispersity (Mw/Mn). After the substitution, the SEC curve shifted to a higher-molecular-weight region (Figure 2.3. 3). For PBTTT-Br, the Mn is 1.5 x 10 4

and Mw/Mn is 1.6, giving the value of Xn,SEC of 20. For PBTTT-Tri, the Mn is 2.0 x 10 4 and Mw/Mn is Unfortunately, when substituted with 2-(4-decyloxy-phenyl)-5-(5-octyl-thiophene-2-yl)- [1,3,4]oxadiazole (0F) in dry DMF under 150°C, precipitation appeared almost immediately after starting the reaction. After removing the solvent DMF, the remained mixture could not readily dissolve in solvents including boiling DMF, DMA, and chlorobenzene. Limited by the solubility, PBTTT-oxa could not be purified and then we didn't characterize it.

Thermal behavior and self-organization study of PBTTT-Tri

The thermal behavior and self-organization of PBTTT-Tri were investigated using polarized-light optical microscopy (POM), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and grazing-incidence wide-angle scattering (GIXS).

Observed under POM, PBTTT-Tri doesn't develop any characteristic optical textures due to the high viscosity of the obtained thin film, and consequently, it is not possible to identify a typical mesophase 8), its hole mobility increases to 1.2 x10 -5 cm 2 V -1 s -1 , which is close to the mobility value for PT10T (~ 1.4 x 10 -5 cm 2 V -1 s -1 ) [START_REF] Schaffer | Linear Optical Properties of a Series of Polyacetylene Oligomers BT -Conjugated Polymeric Materials: Opportunities in Electronics, Optoelectronics, and Molecular Electronics[END_REF] , a side-chain polymer presenting also triphenylene mesogens as side groups and regioregular polythiophene as the backbone.

Conclusion

To sum up, in this section, we designed two new side-chain liquid crystal polymers (PBTTT-Tri and PBTTT-oxa), presenting poly (2,5-bis(3-alkylthiophene-2-yl)thieno [3,2-b]thiophene) as backbone.

However, due to the solubility, only PBTTT-Tri was successfully synthesized and its structure was well characterized by NMR and SEC measurements.

First, we reproduced the monohydroxy triphenylene derivative (Tri) and 2-(4-decyloxy-phenyl)-5-(5octyl-thiophene-2-yl)- [1,3,4]oxadiazole (0F) as side groups, according to the optimized procedures.

Second, we successfully synthesized the desired BTTT monomer in five steps, followed the microwave-assisted Stille polycondensation to prepare the precursor PBTTT-Br, with a quite high yield of 90%. Finally, two polymers (PBTTT-Tri and PBTTT-oxa) were prepared via Williamson ether reaction, but only pure PBTTT-Tri was obtained, in a yield of 80%.

Subsequently, we investigated the thermal behavior and self-organization property of PBTTT-Tri.

The polymer presents liquid crystalline properties and self-organizes in a supramolecular arrangement with the alternation of triple rows of triphenylene columns and the backbone monolayer parallel to the substrate plane. A first attempt to evaluate its preliminary charge transport properties was performed in OFET configuration. PBTTT-Tri exhibits p-type conduction and its hole mobility in the saturated regime is around 1.2 x 10 -5 cm 2 •V -1 •s -1 . The mobility value could probably be improved by optimizing the conditions for constructing the OFET device, for example, adding an OTS layer to promote the orientation of the film, or adopting other OFET architecture.

Chapter 3 TADF polymers for organic light-emitting diodes (OLEDs)

Organic light-emitting diodes (OLEDs) have achieved a great breakthrough and reached the stage of commercialization since the pioneering work of demonstrating the first practical organic electroluminescent diode utilizing a fluorescent organic material as the emitter by C.W.Tang and VanSlyke in the 1980s. 154 OLEDs are a promising alternative to LCDs for display fabrication, as

OLEDs feature high efficiency, good image quality, large viewing angle, and multicolor emission. In addition to these merits, the OLEDs have no demand for blacklightning and can be deposited on either rigid or flexible substrates (glass, silicon as well as plastics), so they're likely to be thinner, lighter, and flexible, consequently, regarded as one of the most important potential candidates for displays and lightening sources. To date, the OLEDs have already developed into three generations: conventional fluorescent OLEDs, phosphorescent OLEDs, and delayed fluorescent OLEDs. Among the 3 rd generation, thermally activated delayed fluorescence (TADF) is the most important branch.

As a result, this manuscript chapter 3 starts with an introduction dedicated to the bibliography (section 3.1): we will briefly introduce the fundamental mechanisms relating to OLEDs, before to detail the fundamental mechanisms of TADF, structure-property relationship in TADF molecules, as well as the photophysics of TADF molecules. Then we will present some examples of the reported TADF materials, including small molecules, dendrimers, and especially linear polymers. Finally, we will give a brief introduction to through-space conjugation.

The following four result sections (section 3.2-3.5) deal with the design, synthesis, and characterization of new π-conjugated polymers, expected to exhibit TADF behaviors. After describing the multi-steps chemical strategy, the photophysical properties of the obtained polymers were investigated. Besides, preliminary electroluminescent properties of S2 polymers were also studied.

More specifically, in section 3.2 and section 3.3, two classes of potential linear TADF polymers (S1 and S2 series) are investigated respectively, based on a donor part fixed in the backbone and acceptor parts endowed in the side chains. In parallel, in section 3.4 and section 3.5 we apply the throughspace conjugation (TSC) system on the TADF platform, by designing two other types of polymers (S3 and S4 series). In the monolayer OLED device architecture, the simplest one (Figure 3.1. 1a), the organic emissive layer acts as both emitter and charge transport material simultaneously. Once the device is electrically excited, electrons from the cathode and holes from the anode are injected into the organic emissive layer. Then both positive and negative charges migrate through the organic emissive layer under the influence of the electric field between the two electrodes. After encountering and recombination, the oppositely charged species can form either singlet or triplet excitons in a singlet:triplet ratio of 1:3 as a result of spin-statistics (Figure 3.1. 2). 155 The carrier injection efficiency, the ratio of excitons formed by recombination to the injected charged species, has an important effect on the device performance.

Bibliography

In order to improve the device performance, multilayer OLED structural architecture was proposed (Figure 3.1. 1b). Where i, V, and L refer to current, voltage, and luminance, respectively, and can be determined by electroluminescence experimental. Equation (3.1.4) is reliable on the assumption that the emission of the OLED device is isotropic.

Efficiency "roll-off" effect, expressed as efficiency dropping quickly with increasing luminance, is the most common phenomenon in OLED devices. It is attributed to the interplay of a range of different non-linear processes, including triplet-triplet annihilation (TTA), singlet-singlet annihilation (SSA), singlet-triplet annihilation (STA), exciton-polaron interaction, field-induced quenching, changes in charge carrier balance and outcoupling efficiency, Joule heating and degradation. To maintain high emission brightness, a higher working voltage is required accompanied by larger power consumption and shorter device lifetime. Therefore, the efficiency "roll-off" effect is a serious problem for practical applications. The possible approaches to suppressing this effect have been put forward: 1) decreasing the exciton lifetime, 2) reducing molecular aggregation, 3) broadening the recombination zone, 4)

reducing the Förster radius, and 5) introducing triplet managers. 162 The device lifetime, defined as the time the luminance drops to one-half of its initial device brightness at a constant current density, is dominated by the degradation of OLEDs. So far, there are essentially three degradation mechanisms: catastrophic failure, "dark spot" growth, and intrinsic degradation. 163 During the last two decades, to slow down the degradation and achieve a long device lifetime, much efforts have been made consisting of choosing organic functional materials with good thermal, electrochemical stabilities, choosing metallic cathodes with a good anti-oxidation ability such as Al, minimizing contamination by strict control of the functional layer growth condition, adopting proper encapsulation for protecting the devices from moisture, oxygen and so on. 164 Emission color quality of OLED devices is tightly associated with the applications in the display and lightening field. Emission color quality is determined by emission wavelength, brightness, luminance, and CIE xy color coordinate. Both of emission wavelength and brightness are subjective attributes of light. The former can be determined by an emission spectrum, whereas the latter can only be perceived rather than be measured objectively. Luminance, the amount of light that emitted from the OLEDs and fell within the given area and direction, is measured as the luminous intensity per unit area in the given area and direction with a SI unit of candela per square meter (cd/m 2 ). C.I.E xy color coordinates, a scientific description of the color regard of luminance, is usually used to determine the content of three primary colors. For example, the CIE coordinate of the pure white emission is (0.33, 0.33). The devices with C.I.E coordinates close to (0.33, 0.33) are probably good candidates for lightening application.

*The development of emissive materials for OLED applications

To date, OLED devices can be classified into three generations with different emission mechanisms:

Conventional purely fluorescent organic light-emitting diodes (FOLEDs), phosphorescent organic light-emitting diodes (PhOLEDs), and delayed fluorescent organic light-emitting diodes.

1 st generation OLED 2 nd generation OLED excitons by RISC process. Therefore, an efficient RISC process is a guarantee for a small , that is to say, a large kRISC and a small ΔEST are necessary for a short DF lifetime. As discussed above, strengthening CT character between the donor and acceptor units is a good way to reducing ΔEST and can be realized by adopting strong donor/acceptor moieties, multiple emitting cores, or distorted backbone structures. [182][183][184] Material stability. TADF material stability is another important factor for the degradation of OLEDs.

The basic demand is that the materials remain stable when exposed to positive or negative polarons and excitons during the device operation. From a chemical structure standpoint, the donor and acceptor moieties, as well as their linkage, should also be stable under charge states. Hence, donor and acceptor moieties featuring large bond dissociation energy (BDE) are favorable for long-term stable TADF emitters. 180 Among multiple candidates, carbazole derived donors and triazine or benzonitrile derived acceptors with high BDE are good choices for stable TADF molecules. For example, TCzIPN

* Photophysics of TADF molecules

As we all know, many TADF materials have been exploited, hence, for the reason of practical application, the investigation of the photophysical properties of TADF molecules has been a crucial issue for the exploit of TADF materials.

Solvatochromism. The solvatochromism effect is the phenomenon that the emission from TADF molecules shows the remarkable bathochromic shift along with increasing the media polarity, due to the stronger stabilization effect of higher polar media on their charge transfer (CT) excited states in contrast to ground states. 192 Usually, TADF molecules show narrow and well-resolved emission in non-polar solvents such as hexane and benzene. With increasing the solvent polarity, the luminescence spectra tend to redshift and become broad and featureless, which is the typical strong charge transfer (CT) character of the excited state (Figure 3.1. 11). When the CT excited states are strong enough, it is even possible that the CT emission is completely quenched in some polar solvents and shows broad and structureless in some nonpolar solvents. It is worth noting that the solvatochromism phenomenon works not only in the solution but also in the condensed state. 193 Take doped EMLs as an example, the TADF materials are dispersed in host matrices which serve as the solid solvent of TADF emitters. CT emission can also be observed in the doped solid films and the molecular polarities of the host materials should have a great effect on the emission colors of TADF devices, so the emission color is tunable by changing the content of host materials in the EMLs for the devices. 178,194 accompanied without phosphorescence, whereas the integral of DF decreases and the phosphorescence appears along with the decreasing temperature. Finally, the DF will be completely inhibited and only phosphorescence exists, when the temperature is low enough. At this point, the thermal energy can't overcome the energy barrier and can't support the triplet-singlet up-conversion of excitons, resulting in the suppression of DF. For most TADF molecules, 77 K (liquid nitrogen) is low enough to the total suppression of DF. However, when the ΔEST is very small, delayed fluorescence (DF) still exists around 77K, because the thermal energy at 77 K is still sufficient to allow the DF process. Therefore, the temperature dependence of DF is a fundamental proof of the source of the delayed components in the TADF mechanism. 178,194 Time-resolved emission spectrum (TRES). As PF and DF arise from the same singlet excited state (ES1), in principle, their emission spectra are identical. However, in some cases, changes happen in the photoluminescence spectra. For example, due to several conformers with slightly different energy levels, the emission shift of the time-resolved emission spectra (TRES) may be observed. TRES is a good alternative to fluorescence steady-state spectroscopy and records the 3D emission spectrum as a function of time. Apart from PF and DF, phosphorescence can also be observed at low temperature.

As phosphorescence comes from the triplet excited state (ET1), the emission spectra of Where E is the energy level, h is the Planck constant, c is the speed of light in vacuum, is the wavelength. As h and c are both constants, E changes in reverse relation to .

ΔEa TADF refers to the activation energy of TADF and can be estimated from Arrhenius plot where DF intensity or is plotted against temperature T. Generally speaking, ΔEa TADF is close to ΔEST and the values often stay in relation ΔEST >> ΔEa TADF . 194 Power dependence of TADF with exciton dose. As both TADF and TTA are thermally activated processes, it's necessary to find out the origin of delayed fluorescence. Power dependence measurement is a convenient approach to distinguish TADF from TTA. In principle, TADF is an intramolecular process and the emission intensity is linearly with exciton dose, whereas TTA is a bimolecular process whose emission intensity shows a quadratic dependence on the exciton dose. 194 However, in some cases, TADF and TTA coexist and can be revealed by power dependence of emission integral that shows slopes between 1 and 2. 178

* Examples of TADF materials

Over the years, many TADF materials have been explored and widely applied in optoelectronic fields including fluorescence imaging 195 , mechanoluminescence 196 , and OLED devices 197 . On the basis of molecular structures, TADF materials can be classified into three groups: TADF small molecules, TADF dendrimers, and TADF linear polymers.

A. TADF small molecules TADF small molecules are the most extensively studied and well-developed materials for OLEDs, due to their high purity, high PLQY, and tremendous possibility with chemical modification. However, their inferior film-forming ability and superior crystallization ability may strongly affect the film morphology and lead to low efficiency and device stability. Various donors and acceptors have been used to manage the TADF characteristics and the full-color emission has been realized. Some TADF small molecules are shown in Figure 3.1. 12. The OLED device using W1 as the emitting dopant displayed superior device performance with an EQEmax of 24.97% at a of 608 nm (doping ratio: 10%). However, the efficiency 'roll-off' effect is very severe and EQE decreased to 8.73% at 100 cd/m 2 and 3.88% at 1000 cd/m 2 .

B. TADF dendrimers

Dendrimers, typically composed of a central core and peripheral branches of dendrons, are a specific category of macromolecules. Due to their distinct structures, dendrimers usually exhibit the advantages of both small molecules and polymers. 202 Dendrimers have a precise molecular structure allowing for reproductivity and their property can be finely tuned through chemical modification. As another advantage, dendrimers have high molecular weight and solution processability. 203 In addition, dendritic architecture prevents it from aggregation and eliminate concentration quenching. 204 Carbazole (Cz) is the most widely used dendron in constructing dendrimers, due to its good holetransporting properties, high thermal stability, and excellent crosslinking abilities. 205 The high steric hindrance from branched Cz is beneficial to reducing the non-radiative decay, avoiding concentration quenching, thus leading to high PLQY. Generally, TADF dendrimers can be divided into conjugated and non-conjugated TADF dendrimers, on the basis of the connection method between the dendrons and the core (Figure 3.1. 13). TADF dendrimers with non-conjugated linkages. In non-conjugated TADF dendrimers, the TADF unit is located at the core and the dendrons connect to the TADF core via non-conjugated aliphatic chains.

The insulating aliphatic linkage guarantees that the TADF character is well retained, and the branched dendrons compensate for the loss of charge injection and transport abilities owing to the nonconjugated linkages. One severe problem of this strategy is that the incorporation of oxygen atoms for the ease of synthesis may change the emission characteristics of TADF units. 204 In POCz-DPS 208

Linear polymeric TADF materials

In addition to small molecules and dendrimers, the TADF character can also be realized in linear polymers. However, linear polymeric TADF-based OLEDs always suffer from low efficiency, short lifetime as well as poor film morphology. To optimize device performance, on one hand, many suitable functional materials are explored by controlling the molecular structures and conformations.

On the other hand, the fabrication condition requires to be well managed. For example, to avoid concentration quenching, most polymeric OLEDs take advantage of the host matrix. However, the introduction of the host may lead to wider luminescence spectra, bathochromic shift (ref-shift), and extra luminescence ascribed to host units. 209 Therefore, it remains a challenge to develop polymeric OLEDs with excellent device performance.

To overcome the limitation, TADF materials need to satisfy the realistic demands as follows. 203 From a point view of production, TADF polymers are fabricated via solution-process, so good solubility and good film-forming ability are necessary in order to produce uniform film morphology without defects or aggregation. For commercial applications, the OLEDs require a long device lifetime and high efficiency. For a long device lifetime, TADF polymers need to possess good thermal, photochemical, and electrochemical stabilities. To achieve high efficiency, similar to TADF small molecules, TADF polymers are required to realize a small singlet-triplet energy splitting (ΔEST) and high photoluminescence quantum efficiency (PLQY) at the same time. As polymers contain a large number of atoms, it is difficult to manage the HOMO and LUMO distribution and eliminate concentration quenching originated from inter-and intra-molecular triplet-triplet annihilation (TTA).

Despite many efforts made to overcome these limitations, TADF was not observed in polymeric architecture until the first linear TADF polymer was reported by Nikolaenko et al. in 2015 210 (Figure 3.1. 15, Table 3.1.2). In this case, suitable donor and acceptor moieties are chosen as distinct monomers to generate the charge transfer emitter (TADF unit) during the polymerization. A third high triplet level component served as a host to isolate the TADF units to inhibit the aggregation and provide the desired solubility and film-forming ability. This promising strategy was successfully applied to a fully solution-processable TADF polymer platform. Followed this pioneering work, many different structural architectures for linear polymeric TADF have been explored. So far, the dominant strategy in the designing of TADF polymers is to take advantage of known TADF small molecules by inserting known TADF-active building blocks into polymeric structures either as pendant groups, as main chain constituents, or as dendrimer cores and dendrons. 211 TADF characters can be realized in either through-bond charge transfer (TBCT) or through-space charge transfer (TSCT). In TBCT systems, donor and acceptor moieties are connected directly by either σ-bond or twisted spacer. In TSCT systems, donor and acceptor units are physically separated. No matter which system is adopted, the HOMO and LUMO are spatially separated. TADF polymers show similar photophysical properties to their small-molecule motifs, such as solvatochromism and oxygen quenching. 177 Based on this strategy, several chemical architectures have been proposed, and they can be classified as linear conjugated TADF polymers and linear non-conjugated TADF polymers, according to the backbone. The photoluminescent and electroluminescent characteristics of typical TADF conjugated polymers are summarized in Table 3.1.1.

* Linear conjugated TADF polymers

Linear conjugated TADF polymers with twisted alternating donor/acceptor units in the main chain.

This strategy (Figure 3.1. 16a) is derived from TADF small molecules. The separated frontier orbital distribution, with HOMO locating on the donor part and LUMO on the acceptor part, would lead to a small ΔEST to facilitate the RISC process.

As an example, in 2016, Adachi et al. developed a class of butterfly-shaped conjugated TADF polymers, 212 namely pCzBP and pAcBP (Figure 3.1. 17), with electron-accepting benzophenone unit linked with electron-donating carbazole or acridine groups, respectively. These TADF polymers showed relatively small ΔEST values (<0.2 eV), which enabled efficient triplet exciton harvesting via up-conversion from T1 states to S1. As a result, pCzBP and pAcBP achieved PLQYs of 23% and 46% in doped films, respectively. The solution-processed doped OLEDs using pCzBP and pAcBP as emitting dopants produced green ( ) and yellow ( ) emission with a maximum external quantum efficiency (EQEmax) of 8.1% ± 0.7% and 9.3% ± 0.9%, respectively.

Besides, the OLEDs based on pAcBP showed a small efficiency roll-off, as the EQE remained 8.0% at a luminance of 1000 cd/A. Linear conjugated TADF polymers with TADF units in the side chain. In this strategy (Figure 3.1.

16b), the TADF units are completely out of the backbone and are introduced as pendants in the side chain, so the TADF effect is not influenced by the backbone. And the conjugated backbone can serve as host materials. Several series of TADF polymers were developed using electron-donating acridine and carbazole groups as the conjugated backbones (Figure 3.1. 19). The acceptors with different electron-accepting abilities were grafted onto the backbone through the nitrogen atom of 9,10-dihydroacridine group with a large dihedral angle to form a pre-twisted intramolecular charge transfer structure (TICT). 216 PAPCC and PAPTC are two alternating TADF copolymers with phenyl cyanogen and dibutyltriazine groups as acceptors, respectively. 216 PAPTC exhibited a small ΔEST of 0.13 eV and high PLQY of 28% in neat films in air, while the ΔEST and PLQY of PAPCC are 0.37 eV and 8%, indicating that strong acceptor is favorable for small ΔEST and high PLQY. Consistent with PLQY, the solution-processed OLEDs based on PAPTC and PAPCC displayed green EL emission ( for PAPTC, for PAPCC) with a maximum EQE of 12.63% and 1.34%, respectively. To optimize the device performance, TAPC was introduced to generate an interfacial exciplex host of TAPC/TmPyPB to restrain triplet quenching of PAPTC emitter. 217 The resulting solution-processed doped OLEDs using PAPTC as the emitting dopant exhibited a superior EQEmax of 14.9% and an

extremely low efficiency roll-off. extremely small efficiency roll-off of 0.5%.

Instead of triazine acceptors with formyl groups, PCzABAx (Figure 3.1. 19) 220 exhibited PLQYs between 35% and 51% in neat films under a nitrogen atmosphere. The non-doped solution-processed OLEDs using PCzABAx as emitters produced green emission and the OLED based on PCzABA10

showed the best device performance with an EQEmax of 10.6% and an extremely small efficiency rolloff with EQE1000 of 10.3%. With benzophenone as acceptor, PABPCx 221 showed small ΔEST (0.09-0.18 eV) and PLQYs from 58% to 77% in neat films under nitrogen atmosphere. The PABPC5-based solution-processed OLED showed the best EL performance with an EQEmax up to 18.1% and also a very slow roll-off with an EQE of 17.8% at a luminance of 1000 cd/m 2 .

Besides, three isomeric benzolpyridine derivates were selected as pendant acceptors to create three

* Linear non-conjugated TADF polymers

As illustrated in Figure 3.1. 25, it's possible to realize TADF in a linear non-conjugated polymer with: a) TADF units in the main chain; b) TADF units in side chain; c) TADF achieved via through-space conjugation (TSC) of donor and acceptor moieties pendant in the side chain. The photoluminescent and electroluminescent characteristics of typical TADF conjugated polymers are summarized in Table 3.1.2. TADF is achieved via through-space conjugation of donor and acceptor moieties pendant in the side chain. In this third approach, the electron donors and acceptors are physically separated resulting in a small overlap of HOMO and LUMO, leading to small ΔEST. Thus, TADF properties could be achieved via the through-space charge transfer (TSCT) effect. These polymers are favorable for blue emission, as a consequence of avoiding emission red-shift originated from extension conjugation. Wang's group successfully prepared several series of TSCT polymers exhibiting a TADF nature. [243][244][245] In these TSCT polymers (Figure 3. is the maximum wavelength of luminescent emission in neat films; ΔEST is calculated from the equation ΔEST = ES -ET, where ES is obtained from the photoluminescent spectrum at room temperature, ET is from phosphorescent spectrum; is the total photoluminescent quantum efficiency (PLQY), is the quantum efficiency contributed by delayed fluorescence, is the lifetime of prompt fluorescence, is the lifetime of delayed fluorescence, , , , were measured in neat films free-oxygen; is the electroluminescent peak; Von is the turn-on voltage at 1 cd/m 2 ; Lmax is the maximum luminance; CE/PE/ EQE refer to maximum current efficiency, maximum power efficiency, and maximum external quantum efficiency, respectively; C.I.E is short of The Commission Internationale de L'Eclairage coordinates, B, G, R, Y, W is short for blue, green, red, yellow, white, respectively; GY is greenish-yellow and BG is bluish-green. a Measured in toluene, b measured in blend film; c measured at 10 cd/m 2 ; d measured in the air; e measured in pristine film at RT in vacuum at 440 nm; f measured in pristine film at RT in vacuum at 520nm 3.1.4 Through-space conjugation (TSC)

The concept of through-space conjugation (TSC) dates back to the study of [2.2]paracyclophane (PCP) in 1949. 249 In PCP, two benzene rings are confined in a coplanar with unusual boat conformation retaining aromaticity. The resulting short distance between the two aromatic rings enables a strong transannular electronic communication, realizing the charge and energy transport. The efficient intramolecular charge transfer (ICT) in the TSC system plays an important role in constructing functional π systems of organic optoelectronic materials. In comparison with the through-bond conjugation (TBC) system, the TSC system with more efficient dispersing charges can effectively slow down the non-radiative charge recombination process and thus stabilize the ICT states, having a positive influence on the fluorescence of molecules with ICT effect. 250

Through-space conjugation (TSC) in construction of TADF emitters

For TADF emitters, one of the vital issues is the pathway to the immoderate overlap of HOMO and LUMO to achieve simultaneously a small singlet-triplet energy splitting (ΔEST) to facilitate the upconversion from T1 to S1 by efficient reverse intersystem crossing (RISC) and a large transition dipole moment to guarantee a high photoluminescence quantum yield (PLQY). TSC system is a good candidate for establishing TADF emitters, especially in the blue regime. As the emission red-shift can be suppressed by avoiding the conjugation extension originated from the through-bond charge transfer (TBCT). The reported TADF emitters with the TSC system, also called through-space charge transfer (TSCT) TADF emitters, can be simply divided into three groups: small molecules, dendrimers, and linear polymers.

A. TSCT small-molecule TADF emitters

In 2015, Swager's group designed and synthesized triptycene-based through-space charge transfer (TSCT) TADF materials TPA-QNX(CN)2 and TPA-PRZ(CN)2 where the donor and acceptor units are endowed in different arms of the triptycene scaffold and physically separated in 120° orientation (Figure 3.1. 32). 255 Through-space conjugation (TSC) enables the intramolecular HOMO/LUMO overlap, leading to TADF effect. Inspired by this finding, they developed U-shaped through-space TADF molecules (XPT, XCT, and XtBuCT, Figure 3 TADF character can also be achieved in TSC systems based on cyclophane (Figure 3.1. 34). Cis-and trans-Bz-PCP-TPA are the first examples of through-space conjugated TADF emitters with a [2.2]paracyclophane (PCP) core and stacked donor-acceptor in coplanar units. 258 Both of the isomers displayed blue TADF emission, short delayed fluorescence lifetime, but low PLQY in films. Cp-ecl and Cp-sta are two isomers consisting of a dithia [3.3]paracyclophane core with a donor ditolylphenylamine unit grafted at the upper deck of cyclophane in an eclipsed and staggered configuration concerning the two acceptor nitrile groups at the lower deck. 259 The isomers showed efficient TADF emission and short reversible intersystem crossing (RISC) lifetimes. Besides, Sp-CzpPhTrz and Rp-CzpPhTrz are sky-blue TADF molecules comprising a triazine acceptor and an indolo [2.2]paracyclophane donor. 260 The indolo [2.2]paracyclophane donor, also named as carbazolophane (Czp), is established by the incorporation of a [2.2]paracyclophane moiety within the carbazole, offering TSCT between the donor and acceptor units. The enhanced donor strength and increased torsion between the donor and phenyl linker make the TADF emission more effective, achieving good device performance with a 17% EQEmax. OLEDs. 264 The TSCT-HABs have a small ΔEST of 0.04-0.08 eV and show distinct delayed fluorescence with lifetimes of 3.16-3.54 μs in the solid-states. Among them, TAc3TRZ3 with strong dendritic teracridan donor exhibits the highest PLQYs of 36% and 63% in neat and doped films, and the associated solution-processed doped OLED displays the best device performance with an EQEmax up to 14.2%.

C. TSCT linear polymeric TADF emitters TSCT linear polymeric TADF emitters have already been described in detail in chapter 3.1.3 and here we make a simple summary. Wang's group developed several TSCT linear polymeric TADF emitters with physical-separated pendant donor and acceptor units, and proved it a promising approach to realize full-color and white emission. [243][244][245] As summarized in Table 3.1.2, the ΔEST of boroncontaining TADF molecules is smaller than 0.1 eV, and the ΔEST of other molecules is even no more than 0.05 eV. The PLQY of boron-containing TADF molecule PTF-20 can reach to 53% in the neat film under N2, and the PLQY of P3-05 is as high as 74% in the same condition. TSCT linear polymeric TADF emitters favor blue emission as a result of avoiding emission red-shift induced by electron delocalization. By managing the electron-withdrawing abilities through changing the substituents, the emission color ranges from deep blue to red. Moreover, white emission is realized by duplex TSCT channels with blue and yellow emission simultaneously. Besides, these TSCT linear TADF polymers exhibit significant AIE phenomena. Besides, Hudson et al. discovered the interfacedependent aggregation-induced TADF character in bottlebrush nanofibers constructed by miktoarm copolymer ACR75-co-TRZ75-BB, due to the formed donor and acceptor interfaces with the nanofibers. 246

Aim and outline of this chapter

In this context, we will present the first investigations carried out in our lab on new light-emitting polymers developed for third-generation OLEDs, based on thermally activated delayed fluorescence (TADF) materials. Indeed, our group recently started the activity in this field, in the framework of a CNRS-JSPS project between OPERA (Kyushu University, Fukuoka, Japan) and IPCM.

Moreover, as explained in a long bibliography section 3.1, the TADF phenomenon is capable of achieving 100% of IQE through up-conversion from the triplet excited state to the singlet excited state.

Besides, the common strategy in designing TADF emitters is playing with electron-donating D and electron-accepting A groups, as well as a separating central core, many macromolecular designs being currently investigated. The aim of our research here is thus to design and develop different families of D-A polymers which are reported in Figure 3.1. 37.

More precisely, two families of polymers will be studied: in section 3.2 and section 3.3, we will investigate the first family consisting of two new series of potential linear TADF polymers (S1 and S2 series) based on a carbazole-based donor backbone and acceptor moieties such as dicyano-benzene or cyano-pyrimidine, grafted as side groups. In section 3.4 and section 3.5, we will investigate the second family consisting of two novel series of potential TADF polymers based on through-space conjugation (TSC) between the same donor and acceptor units as those utilized in the first family (S3 and S4 series). Concerning these four series of novel polymers designed as potential TADF materials, in all cases, we first describe their synthesis, before to fully characterize them. In particular, their photophysical properties will be checked in solution, in solid-state but also in device configurations, to try to find rules and structure/properties relationships that could be later on generalized. Preliminary solutionprocessed OLED devices are eventually tested, in collaboration with OPERA laboratory (Japan).

Linear conjugated TADF polymers based on 26IPNDCz

26IPNDCz, comprising a dimeric phenylcarbazole and four cyano substituents on the phenyl rings, is an "acceptor-donor-acceptor" (A-D-A) type TADF monomer. As reported by Adachi's group 265 , 26IPNDCz possesses the twisting angle between the carbazole and isophthalonitrile planes of 69°, leading to the adequate HOMO-LUMO separation. 26IPNDCz exhibits blue-green emission with a small ΔEST of 0.06 eV and PLQY of 72% in doped DPEPO film (10 wt%). The lifetime of prompt and delayed fluorescence are 28 ns and 9.2 s, respectively, in oxygen-free toluene at room temperature.

The OLED device based on 26IPNDCz doped DPEPO film (10 wt%) possesses an EQEmax of 4.3% at 100 mA/cm 2 . and the yield was as high as 74%. On the other hand, 2D was synthesized by lithiation with freshly prepared LDA, followed by the addition of an excess of C2Cl6. The total yield for this reaction reaches 51%. 2E was obtained through the reaction between 2A and 2D in the presence of NaH. As shown in the 1 H NMR spectrum in THF (Figure 3.2. 4), the signals at 8.45, 7.59, and 7.12 ppm are attributed to the protons of 4-, 1-and 2-position of carbazole unit, respectively, while the doublet signal at 8.36 ppm and triplet signal at 7.95 ppm belong to the protons of isophthalonitrile units. The chemical shifts and the integrals of all signals are in agreement with the molecular structure of 2E, confirming the success of the reaction. However, the yield of this reaction is low (10%). This low yield may originate from the elimination reaction which plays a dominant role under the used conditions (NaH, dry DMF, Ar, RT, 24 h), compared to the substitution reaction. To improve the yield, other reaction conditions were attempted, including the use of K2CO3 instead of NaH, the increasing of temperature until 80-120°C, and the change of the reaction time. However, all these efforts failed. As our objective was mainly to prepare the target monomer, we didn't go further to improve the reaction conditions.

Scheme 3.2.3

The synthetic pathway towards S1 polymers. Condition: 1) NBS, dry DMF, RT, 24 h, 76%; 2) NaH, dry DMF, RT, argon, 4 days, 53%; 3) bis(pinacolato)diboron, Pd(dppf)2Cl2, KOAc,1,4dioxane,argon,85 o C,24 h,[START_REF] Spencer | The First Direct Experimental Comparison between the Hugely Contrasting Properties of PEDOT and the All-Sulfur Analogue PEDTT by Analogy with Well-Defined EDTT-EDOT Copolymers[END_REF][START_REF] Wang | Organic Semiconductor Crystals[END_REF] LDA, C2Cl6, dry THF, Ar, 51%;5) NaH, dry DMF, Ar, RT, 24 h, 10%; 6) Pd(PPh3)4, K2CO3, THF/H2O, 85 o C, 3 d, 15-30%. The dispersity and molecular weight of S1 polymers were determined by Size exclusion chromatography (SEC) in THF with polystyrene as standard (Figure 3.2.8). Their relative numberaverage molecular weights (Mn,SEC) are 4.5-5.7 kDa, with the dispersity (Mw/Mn) of 1.20-1.41, indicating a degree of polymerization (Xn,SEC) of 7-10 (see Scheme 3.2.3).

The elemental analysis (EA) was also used to determine the composition of the polymers. From Table 3.2.1, we can see that there is a large difference between the results from EA and the theoretical values.

The possible reasons are: 1) for each polymer, the sum of the ratios of C, H, and N atoms is not 100%, revealing that Br exists in the polymers as end group, while the theoretical values are calculated without considering the end groups; 2) In polymerization, the real ratio of the components in the polymers is not equal to the feeding ratio: even for alternating polymers (S1-11 and S1-11-L), the real composition presents three possibilities. a result from elemental analysis; b theoretical values from feeding ratio without considering end groups

Photophysical properties

After the structural characterization, the steady-state and the time-resolved fluorescence measurements of S1 polymers were recorded in both solution and solid-state, in collaboration with the OPERA laboratory of Prof. Chihaya Adachi at Kyushu University. Indeed, in the scope of the JSPS core-tocore program between OPERA and IPCM, I had the opportunity to spend one month at OPERA lab in 2019.

In dilute solution

Steady-state measurements

The steady-state UV-vis absorption and photoluminescence (PL) spectra of S1 polymer series in dilute toluene and chloroform solutions are depicted in Figure 3.2.9 and Figure 3.2.10, respectively, and their photophysical properties in solvents are summarized in Table 3.2.2. The photoluminescence quantum yields (PLQYs) of the polymers were measured in the air atmosphere and after nitrogen-bubbling for 15 min. The S1 polymers achieve much higher PLQY in toluene than that in CHCl3, and S1-11-L possesses the highest PLQY of 29% in toluene in the N2 atmosphere. The S1 polymers exhibit similar UV-vis absorption spectra and their main characteristic peaks are located at 306-309 nm in toluene and 308-311 nm in CHCl3, corresponding to the π-π transition of the backbones. The small red-shift of the main peak for each polymer in CHCl3 compared to that in toluene results from the small solvatochromism effect in their ground state. Besides, all S1 polymers exhibit weak absorption around 400 nm, ascribed to the intramolecular charge transfer (CT), characteristic of D-A systems.

The PL spectra of S1 polymers in toluene are quite different from that in CHCl3. In toluene, all PL spectra are broad, and S1-11 and S1-11-L exhibit a single emission peaked at 534 nm and 528 nm, respectively, attributed to the intramolecular charge transfer (CT) transition from the D-A TADF chromophore. However, S1-91 shows a dual emission: one weak emission peaked around 425 nm assigned to the π-π transition from carbazole fragments, and another brad and intense band peaked at 525 nm results from the CT emission of TADF units. Note that the dual emission also indicates the incomplete inter/intra-chain energy transfer from the carbazole fragment to the TADF unit. In CHCl3, the PL spectra show multiple featureless emissions. This is due to the decrease of the intensity of the CT band in a polar solvent that accentuates the contribution of other emissions. The main peaks are located at 568, 561, and 562 nm for S1-11, S1-11-L, and S1-91, respectively, corresponding to CT emission of the TADF chromophore. The obvious redshift of these peaks in CHCl3 in comparison with toluene is consistent with the D-A character of the materials. The emissions (374 nm) are assigned to the π-π transition from carbazole fragments.

According to the absorption and emission spectra, the Stokes shift can be calculated for S1-11, S1-11-L and S1-91 as 228 nm (13953 cm -1 ), 220 nm (13528 cm -1 ) and 216 nm (13315 cm -1 ) in toluene and 260 nm (14862 cm -1 ), 252 nm (14537 cm -1 ) and 251 nm (14361 cm -1 ) in CHCl3, respectively.

The photoluminescence quantum yields (PLQYs) of the polymers were measured in the air atmosphere and after nitrogen-bubbling for 15 min. As generally observed for D-A systems, the S1 polymers achieve much higher PLQY in toluene than that in CHCl3, and S1-11-L possesses the highest PLQY of 29% in oxygen-free solution.

Time-resolved measurements

The fluorescence decays of S1 polymer series in toluene at room temperature were measured as well, by time-resolved fluorescence spectroscopy with time-correlated single-photon counting (TCSPC) in both air and nitrogen atmosphere (Figure 3.2.11). Both PF and DF components are clearly observed in decay curves. As shown in Table 3.2.3, the PF and DF lifetimes can both be calculated using the mono-exponential function and the data are summarized in Table 3.

In solid-state

Steady-state measurements

The steady-state UV-Vis absorption and PL spectra of S1 polymers in the neat film are shown in Figure 3.2.12 and the photophysical parameters are reported in Table 3. 217 nm (13148 cm -1 ), 206 nm (13080 cm -1 ), and 215 nm (12878 cm -1 ). To estimate the energy levels of excited states of S1 polymers in neat film, their singlet and triplet energies (ES and ET) were determined according to the fluorescent and phosphorescent spectra, PLQYs of S1 polymers (Table 3.2.4) in the neat film was much lower than that measured in toluene, probably due to the aggregation-caused quenching. Taking HOMO, LUMO, and triplet energy level into account, mCP (1,3-Bis(N-carbazolyl)benzene) was chosen as the host material to fabricate blend films. Therefore, the PLQYs of the obtained blend films were measured. As shown in Table 3.2.5, PLQYs in mCP doped films with different ratios of S1 polymers increase with the decrease content of the polymer concentration, indicating the reduction of the concentration quenching. For S1-91, PLQY doesn't increase too much with the decreasing content of the polymer, probably since TADF chromophores are already dispersed well along the polymer backbone.

Time-resolved measurements

The fluorescence decays of S1 polymers in neat films at room temperature were also measured by The temperature dependence of the transient PL decay spectra of S1 polymers in neat films was further investigated by a streak camera from 100 to 300 K in vacuum. As shown in Figure 3. In contrast to the PF decays which show almost no variation with temperature, delayed fluorescence decay spectra show clear temperature dependence for the three S1 polymers and they can be fitted with a bi-exponential function (details in Table 3.2.7, Table 3.2.8, and Table 3.2.9). For S1-11 and S1-91, the DF lifetime increases with decreasing temperature from 300 K to 100 K. That is consistent with a longer triplet lifetime at low temperature, resulting from a slower reverse intersystem crossing rate according to the TADF mechanism. The fluorescence decays of S1 polymer doped films (10% in mCP) at room temperature were also investigated by time-resolved fluorescence spectroscopy with TCSPC in both air and argon

Conclusion

To summarize, we designed and synthesized a new series of green-emitting polymers with poly (3,6carbazole) as backbone and isophthalonitrile as side groups. The polymers were successfully prepared via Suzuki polycondensation. The structures of monomers and S1 polymer series were characterized by NMR, SEC, and elemental analysis.

The photophysical properties of S1 polymers were investigated in detail by both steady and timeresolved measurements. More specifically, the absorption, emission, and phosphorescence (17K) spectra were recorded in solution and solid-states. From these spectra, we determined the singlet and triplet energy levels, the optical bandgap, and Stokes shifts of these polymers. Small ∆EST values (0.01-0.02 eV) were also estimated suggesting possible TADF properties. Moreover, photoelectron spectroscopy in neat films, combined with optical measurements, was used to determine the HOMO/LUMO energy levels of polymers.

From the time-resolved measurements, we can confirm that S1-11, S1-11-L, and S1-91 exhibit TADF activity both in solution and solid-state. Due to aggregation-caused quenching, PLQYs of S1 polymers in neat films are much lower than those in diluted degassed toluene solutions. mCP was chosen as the host material for blend films to improve PLQYs in solid-state up to 14 times. Among the polymers, S1-11-L holds the highest PLQY of 29% in oxygen-free toluene. In a neat film, a low PLQY of 1.7% in argon can be obtained and this value increases to 24% by preparing 5 wt% mCP doped film.

Compared to the reported TADF polymers, the PLQYs of the S1 polymer series are quite modest, but the electroluminescent properties (device performance) of this series should be investigated in the near future.

Linear conjugated TADF polymers based on Pm5

Pm5 is a 'donor-acceptor' type TADF molecule 266 , with 9,9-dimethylacridine (DMAC) as the donor part bridged via a phenylene ring to a cyano-pyrimidine acceptor unit. As shown in Figure 3.3.1, Pm5 possesses a highly twisted configuration (with a large dihedral angle around 88°) between the DMAC ring and the phenylene bridge, presumably owing to strong ortho-ortho interaction between acridine and central phenylene ring. In the meanwhile, we observe a planar conformation (with a dihedral angle close to 0°) between the CN-substituted pyrimidine and the phenylene ring. cd/A, and a power efficiency of 116.3 lm/W together with CIE coordinates of (0.34, 0.57).

Design, synthesis, and structural characterization

As Pm5 exhibits excellent TADF properties, we proposed to utilize this TADF chromophore into copolymers, in following the same strategy as in section 3.2. Hence, Pm5 needs to be brominated on the 3,6-positions to obtain the monomer 3D (Scheme 3.3.1). Considering the solubility, the comonomers 2B and 2C were also chosen, as carbazole provides the excellent hole-transporting ability, while branched long alkyl chains offer good solubility. Before polymerization, we prepared again 2B

and 2C following the same synthetic procedures as described in section 3.2.

As shown in scheme 3.3.1, the monomer 3D was synthesized in 4 steps: we started from the coupling reaction between 9,9-dimentyl-9,10-dihydroacridine and 1-bromo-4-chlorobenzene in toluene, using Pd2(dba)3, P(t-Bu)3/HBF4 and t-BuONa as the catalytic system and obtained the molecule 3A with a yield of 65%. Then, the -Cl group of the molecule 3A was converted to pinacolborane group of the molecule 3B in a yield of 52%, catalyzed by Pd(OAc)2, Sphos, and KOAc. The third step is a "typical" Suzuki coupling reaction under the function of Pd(dppf)2Cl2 and Cs2CO3, to gain the TADF chromophore 3C (Pm5 in the literature 266 ) with a yield of 52%. The last step is the "traditional" bromination reaction using NBS, and then, after purification, the monomer 3D was obtained with a yield of 77%. K2CO3 as the catalytic system and THF/H2O as the solvent and then stirring at 85 °C for 3 days under argon atmosphere. After purification, pale yellow solids were obtained and their conversion is 28-40%.

In terms of the molar feed ratio of acridine and carbazole units in the backbone, these polymers were denoted as S2-11, S2-31 and S2-91. Among them, S2-11 is alternating copolymers. The obtained polymers can be readily dissolved in common polar organic solvents, including THF, DCM, and CHCl3. The structures of monomers and polymers were confirmed by NMR measurements (Figure 3.3.3) and elemental analysis (Table 3 .3.1). Compared to the NMR spectra of monomers, the signals of the polymers in NMR spectra are broad and overlapped. The signals around 4.25 ppm are attributed to the protons of -CH2 groups connected to the N atom of carbazole units, while the overlapped signals in the range of 0.8-2.5 ppm belong to the alkyl protons in the side groups attached to the carbazole groups as well as the methyl groups in the acridine units. Besides, the signals from 9.0 to 9.5 ppm are ascribed to the acridine rings.

The dispersity and molecular weight of S2 polymers were also determined by SEC in THF at 40 °C with polystyrene as standard (Figure 3.3.4). Their relative number-average molecular weights (Mn,SEC) are 3.4-4.2 kDa, with the dispersity (Mw/Mn) of 1.28-1.56. The molecular weights are not so large and the number of repeating units (Xn,SEC, see the structures in scheme 3.3.1) are calculated to be 4.3-5.1, thus these polymers can also be regarded as oligomers.

The elemental analysis (EA) was also used to determine the composition of the polymers. As shown in Table 3.3.1, similar to the results of the S2 polymer series, there is also a difference between the real and the theoretical values. This phenomenon results from the remained Br or pinacol ester in the polymers, as well as the theoretical values calculated from the feeding ratio of monomers. Based on the previous reports, it can be deduced that the TADF chromophore in S2 polymers consists of the Pm5 unit and the two directly connected carbazole rings. Therefore, these polymers would display a similar main emission band, which is attributed to intramolecular CT from the same TADF chromophore. However, the main emission maxima of these polymers in toluene are gradually redshifted with increasing Pm5 content ratio in the polymers, which is another indication of the existence of aggregation in toluene.

According to the absorption and emission spectra, the Stokes shift was calculated as well for S2-

Time-resolved measurements

The TADF characteristics of the polymers in toluene were further confirmed by time-resolved fluorescence spectroscopy with time-correlated single-photon counting (TCSPC). As demonstrated in and the PF and DF lifetimes were examined in detail.

In each PL decay curve, PF and DF components can be easily observed and be fitted with a monoexponential function, respectively. The data are recorded in Table 3.3.3. The DF ratio of each polymer is not so high (< 25%). Moreover, short delayed components (< 1µs) were clearly observed after nitrogen-bubbling for 15 min, indicating that the delayed components are originated from the triplet states of the polymers. The obvious existence of DF components is consistent with the large PLQY difference (2-3 folds) in the air and nitrogen atmosphere. The temperature dependence of S2 polymers in neat films was also measured by streak camera from 50 to 300 K and their PL decay curves were shown in Figure 3. 3.3.7, 3.3.8, and 3.3.9, with the temperature decrease, the DF lifetimes increase, which is consistent with the TADF mechanism. The temperature dependence of the transient PL decay spectra of S2 polymers in CBP doped film ( 10wt%) was also investigated by a streak camera from 50 to 300 K in vacuum (Figure 3.3.14). We can clearly observe two components in all PL decay curves, among them, the PF components are overlapped with each other. While the delayed components show clear temperature dependence and can be fitted with a bi-exponential function (Table 3.3.11, Table 3.3.12, and Table 3.3.13). For each component, the DF lifetime increases with decreasing temperature. That is consistent with the TADF mechanism in which a longer triplet lifetime at lower temperature results from a slower RISC rate.

Note that, as also observed for neat films, the DFs in CBP doped films under vacuum are much longer than those under argon with values at room temperature about 3.3-18.7 µs, in vacuum vs 2.4-5.3 µs under Ar flow (Table 3 .3.11, Table 3.3.12 and Table 3.3.13 vs Table 3.3.12). However, these DF components are still small and, as mentioned previously, indicate a rapid RISC potentially interesting in device configuration (low the roll-off). Note also that, here again, the previous PLQYs in CBP doped film determined under argon flow (Table 3 .3.13) are probably underestimated. spectra were recorded. From these spectra, we determined the singlet and triplet energy levels, the optical bandgap, and Stokes shifts of these polymers. Small ∆EST values (0.06-0.1 eV) was also estimated suggesting possible TADF properties., Also, the HOMO/LUMO energy levels of S2 polymers were determined in neat films by photoelectron spectroscopy, combined with optical measurements.

From the time-resolved measurements, we can confirm that all S2 polymers exhibit TADF activity.

Among the polymers, S2-31 holds the highest PLQY of 44% in oxygen-free toluene. In the neat film, low PLQYs from 6% to 23% in argon can be obtained and a value as high as 44% can be observed by preparing 5 wt% CBP doped film (S2-11).

One solution-processed OLED device using S2-11 CBP blend film as the EML was prepared and achieved a maximum luminance (Lmax) of around 5600 cd/m 2 , with an EQE of 1.9%. The electroluminescent properties could be further optimized by changing the parameters of the device fabrication, as well as doped emitting films and other layers.

Through-space charge transfer (TSCT) TADF polymers based on 26IPNDCz

As mentioned in section 3.1.5, compared to the through-bond conjugation (TBC) system, the throughspace conjugation (TSC) systems possess more flexibility and possibilities in designing optoelectronic materials with stable ICT states, owing to its non-covalent structure and spatial delocalization of π electrons.

As described in section 3.2, S1 polymers with TBC system, derived from 26IPNDCz 265 , have been proved to be TADF polymers, while their PLQYs in solid-state are only modest.

Therefore, in this section, to achieve higher PLQY, we tried to apply the TSC system on the donor (carbazole) and acceptor (isophthalonitrile) units utilized in S1 polymers. Thus, we designed and synthesized a new series of vinyl polymers S3 (Figure 3.4.1) which are expected to exhibit TADF character via through-space charge transfer (TSCT). In this context, we will present the design, synthesis, structural characterization, and photophysical properties of such polymers. Size exclusion chromatography (SEC) was used to study the dispersity and molecular weight of S3

polymers (Figure 3.4.4). The relative number-average molecular weights (Mn,SEC) of these polymers are in the range of 18-27 kDa, with the dispersity (Mw/Mn) of 1.40-1.76. The real ratios of 4A and 4E in copolymers were calculated as well from elemental analysis results (Table 3.4.1) and the resulting degree of polymerization (Xn,SEC) is between 67 and 103. Besides, the sole SEC peaks confirmed that no small molecules (oligomers or monomers) remain in the polymers.

Photophysical properties

After the chemical structure characterization, the photophysical properties of S3 polymers in both solution and solid-states were measured at the OPERA laboratory of Prof. Chihaya Adachi at Kyushu University in the scope of the JSPS core-to-core program. Unfortunately, I couldn't go to OPERA myself in 2020 due to the COVID19 pandemic.

In dilute solution

Steady-state measurements

The steady-state UV-vis absorption, photoluminescence (PL), and phosphorescence spectra of S3 We can note that in solution, the DF lifetimes are relatively rapid for these polymers, as an example, S3-91 presenting a DF lifetime of about 0.23 µs. The prompt and delayed lifetimes were calculated from the PL decay curves in nitrogen, with a bi-exponential function.

In solid-state

Steady-state measurements

The steady-state UV-Vis absorption, PL, and phosphorescence spectra of S3 polymers in the neat film are shown in Figure 3.4. 7. The absorption spectra show main peaks at 285, 291, and 296 nm for S3- The average lifetime is calculated using

Besides, the temperature-dependent PL decay spectra of S3-91 were recorded by a streak camera from 50 to 300K, as represented in Figure 3.4 10. The PL decay curved could be divided into two parts:

prompt and delayed components. The prompt components of all curves are overlapped with each other, illustrating that the prompt fluorescence shows almost no variation with temperature, which is consistent with the negligible internal conversion. The delayed fluorescence changes vs temperature can be fitted with a bi-exponential function. However, the lifetimes of the delayed component, summarized in Table 3.4. 6, didn't increase along with the decreasing temperature, suggesting that S3-91 presents in the neat film no or weak TADF properties.

Conclusion

In this section, we designed and synthesized a new series of vinyl polymers namely, S3 polymers, with TSB interactions between the donor (carbazole) and the acceptor (isophthalonitrile) units. Before polymerization, the donor and acceptor monomers were successfully synthesized in a 6-step procedure.

The S3 polymer series were prepared via radical polymerization at 60°C for 48h with 5% AIBN as the initiator and dry toluene as the solvent. The chemical structures of the monomers and polymers were confirmed by the proton and carbon NMR spectra. SEC measurements demonstrated that S3 polymers hold the relative number-average molecular weights (Mn,SEC) of 18-27 kDa, with the dispersity (Mw/Mn) of 1.40-1.76, and the degree of polymerization (DP) of 67-103. Besides, the real components in these polymers were further calculated from the result of elemental analysis.

Subsequently, we investigated the photophysical properties of these materials in both solution and neat film by steady-state and time-resolved measurements. The UV-vis absorption, photoluminescence, and phosphorescence spectra of S3-11, S3-31, and S3-91 in dilute toluene and neat films were measured.

The optical energy level (Eg), singlet and triplet energy levels (ES and ET) of polymers were determined from the onsets of UV-Vis absorption, photoluminescence, and phosphorescence spectra in neat film.

For each polymer in toluene solution, their transient PL decay curves under air and nitrogen atmosphere show distinct changes with the varying oxygen content, suggesting that triplet states are involved in photoluminescent properties. This observation is also in agreement with the PLQYs changes in different atmospheres. In toluene, the PLQYs are 46-65% and decrease a lot in presence of oxygen. And in neat films, the PLQYs are only 13-15%, revealing the presence of aggregation-caused quenching in solid-state.

To further study the PL decay behavior of these polymers, a streak camera was utilized to record the time-resolved transient PL spectra. And the temperature dependence of PL decay of S3-91 was further studied from 50 to 300K in vacuum. Although the DF lifetimes of S3-91 at each temperature was fitted with a bi-exponential function, the resulting DF lifetimes don't show a clear temperature dependence, demonstrating that S3-91 presents no or very weak TADF properties in solid-state. This could be consistent with the relatively large ΔEST (>0.27 eV) observed for this polymer series in neat film. Additional studies such as in host/guest systems should be performed to investigate more deeply the potential TADF activity of these materials.

dimethyl-9,10-dihydroacridine and the -Br group of 1-bromo-4-vinylbenzene, using Pd2(dba)3 as the catalyst, P(t-Bu)3/HBF4 as the ligand, and t-BuONa as the base, with a yield of 65%.

On the other hand, the electron-accepting monomer 5B was successfully synthesized via a Suzuki coupling between the commercially available 2-chloropyrimidine-5-carbonitrile and 4vinylphenylboronic acid molecules, using Pd2(dba)3 as the catalyst, Sphos as the ligand, and K3PO4 as the base, with a yield of 20%. The possible reason for the relatively low yield is that the used catalystligand-base system is probably not suitable for this reaction. For 5B, the protons of vinyl groups (-CH=CH2) are located at 6.85, 5.95, and 5.42 ppm, and the protons of aromatic rings are ranging from 9.03 ppm to 7.58 ppm. In each spectrum, the integrals of all peaks are consistent with the molecular structure.

Based on the chemical structure evidence from NMR spectra, we used these monomers without further purification. S4 polymers with various ratios of the electron-donating and electron-withdrawing units were prepared from the radical polymerization in dry toluene at 60 o C for 48 h, using 5A and 5B as monomers together with 5% AIBN as initiator. More precisely, we isolated six S4 polymers, namely S4-11, S4-31, S4-51, S4-91, S4-955, S4-991, corresponding to the different feed ratios of 5A : 5B = 1:1, 3:1, 5:1, 9:1, 95:5, 99:1, respectively. We can observe that these polymers are pale yellow solids and their color is darker with the increasing feed ratio of the acceptor (5B). After polymerization, as observed in figure 3 We can also observe from the zoom of the proton NMR spectra (Figure 3.5. 4) that the peaks from 7.9 to 9.0 ppm gradually vanish, and the peaks in the range from 5.70-7.09 ppm become larger and larger, with increasing the feed ratio of the electron-donating unit (5A), also revealing that the real ratios of the electron-donating unit (5A) are increasing with the increasing feed ratios of 5A. The real ratio of 5A and 5B in our S4 copolymers were calculated from elemental analysis and the main results are reported in Table 3.5. 1. From all these data, we can essentially say that the degree of polymerization (Xn,SEC) is between 70 and 174. Furthermore, the sole SEC peaks are confirming the NMR conclusions, i.e. no residual monomers or oligomers are remaining.

Photophysical properties

After the structural characterization, the photophysical properties of S4 polymers (S4-11, S4-31, and S4-91) in both solution and solid-states were measured at the OPERA laboratory in the scope of the JSPS core-to-core program. Unfortunately, I couldn't go to OPERA myself in 2020 due to the COVID19 pandemic.

In dilute solution

Steady-state measurements

The steady-state UV-vis absorption, photoluminescence (PL), and phosphorescence spectra of S4-11, S4-31, and S4-91 in dilute toluene solution are depicted in Figure 3.5. 6, and data are summarized in Table 3.5. 2. The main absorption bands of S4-11, S4-31, and S4-91 are located at 299, 292, and 290 nm, respectively, and are mainly attributed to the π-π transition of unsaturated aromatic side groups.

Moreover, the absorption spectrum of S4-11 shows a weak and broad CT band in the range of 350-400 nm, originating from the intramolecular charge transfer (CT) between the donor and acceptor units.

Concerning fluorescence properties, S4-91 demonstrated a dual emission: the main emission, attributed to the intramolecular charge transfer (CT) transition, shows a maximum at 565 nm and its intensity decreases a lot when changing from N2 to O2 atmosphere (see Figure 3.5. 6b). This indicates that this emission is originated from the triplets, which are effectively quenched by oxygen; the other emission maximum is situated at 374 nm, ascribed to the residual emission of acridine fragments.

Note as well that the PL spectra of S4-11 and S4-31 are almost identical to that of S4-91 in the range of 400-800 nm, displaying a unique emission band located at 564 and 566 nm, respectively. According to the absorption and emission spectra, the Stokes shift in toluene can be calculated for S4-11, S4-31, and S4-91 as 265 nm (15714 cm -1 ), 274 nm (16579 cm -1 ), and 275 nm (16784 cm -1 ), respectively. The photoluminescence quantum yields (PLQYs) of S4-11, S4-31, and S4-91 were measured both in the air atmosphere and after nitrogen-bubbling for 15 min. As shown in Table 3. The prompt and delayed lifetimes were calculated from the PL decay curves (time scale: 5000ns) in nitrogen, respectively, with a bi-exponential function.

In solid-state

Steady-state measurements

The steady-state UV-Vis absorption, photoluminescence, and phosphorescence spectra of S4 polymers in the neat film are shown in Figure 3.5. 8 and the data are summarized in Table 3. The Stokes shift can be calculated and equal for S4-11 (S4-31 and S4-91 respectively) in neat film, 243 nm (15152 cm -1 ) (247 nm (15611 cm -1 ) and 232 nm (15326 cm -1 ), respectively).

As represented in Figure 3 Finally, the PLQYs of S4-11, S4-31, and S4-91 in neat films under nitrogen atmosphere were measured to be 23, 33, and 53%, respectively, which are lower than those in dilute toluene (57-63%).

This indicates that aggregation-caused quenching must exist in these neat films, especially in the case of S4-11 and S4-31.

Time-resolved measurements

To further confirm the TADF behavior of S4 polymers in neat film, streak camera measurements were utilized to investigate time-resolved transient PL spectra in vacuum at room temperature.

As shown in Figure 3.5. 10, the transient PL spectra were recorded with two time-scales: 50 ns and 50 μs. All these polymers exhibit distinct prompt and delayed components, corresponding to the TADF nature, and the prompt component can be fitted with a mono-exponential function, while the delayed component is fitted with a bi-exponential function (calculation details in Table 3.5. 4). The polymers exhibit longer emission lifetimes when the acceptor content in backbones decreases (Table 3 .5.5). This behavior is consistent with the higher PLQYs also observed and could be explained by the reduction of the concentration quenching from S4-11 to S4-91. As S4-91 presents the highest PLQY and largest DF component, the temperature-dependent timeresolved measurements of this polymer were performed as shown in Figure 3.5. 11, and the data are summarized in Table 3.5. 6. is too low for the polymers to realize the up-conversion from the triplet to singlet state.

Conclusion

In this section, we designed and synthesized a new series of vinyl polymers namely, S4 polymers, with TSB interactions between the donor (acridan) and the acceptor (cyano-pyrimidin) units. The two donor and acceptor monomers were successfully synthesized from commercially available starting materials, respectively, using Pd2(dba)3 as the catalyst. The S4 polymer series were prepared via radical polymerization at 60°C for 48h with 5% AIBN as the initiator and dry toluene as the solvent. The chemical structures of the monomers and polymers were confirmed by NMR and the real ratio of the electron-donating and electron-withdrawing units were further calculated from elemental analysis.

Moreover, SEC measurements demonstrated that the relative number-average molecular weights (Mn,SEC) of these polymers range from 19 to 39 kDa, with a relatively low dispersity (1.44-1.98).

Small ΔEST values of 0.03-0.05 eV indicate a possible easy up-conversion from triplet to singlet states (RISC). The investigation of the photophysical properties of these polymers in solution and neat film was carried out. In toluene, the PLQYs are about 57-63% in oxygen-free toluene and the photoluminescence time-resolved measurements showed proper TADF properties with µs scale fluorescence lifetimes. In solid-state (neat film), the PLQYs of polymers reached relatively high values such as 52% for S4-91 which also presents proper prompt and delayed components, confirming the TADF properties of these through-space conjugated macromolecular systems. 72, 157.89, 141.72, 137.10, 125.94, 31.93, 31.40, 30.96, 29.35, 29.27, 29.14, 22.75, 14.19.

5-n-Octylthiophene-2-carboxylic acid (0B).

The preparation of Jones reagent: H2SO4 (98%, 30 mL) was slowly added into water (120 mL). After cooling down to room temperature, CrO3 (39 g, 0.39 mmol) was dissolved into the above solution. Jones reagent (12 mL) was added to a stirred solution of 5-n-octylthiophene-2-carbaldehyde (2.89 g, 12.9 mmol) in acetone (40 mL) in the ice water bath (<20 o C). The mixture was stirred at room temperature overnight. The solution was decanted from the green precipitation of Cr2O3 and concentrated to about 10% of volume. The precipitation was washed with ether. Combining the ether solution and concentrated acetone solution, the resulting solution was washed with water to remove sulfuric acid (3 x 30 mL). The organic phase was extracted with a saturated NaHCO3 solution (3 x 30 mL). HCl (37%) was added into NaHCO3 solution until a white precipitate appeared. After filtrating, a white solid was dried in vacuum (2.6 g, 84%). Hz, -CH3). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (75 MHz, CDCl3): δC = 168.06, 156.29, 135.49, 129.90, 125.69, 31.97, 31.53, 30.73, 29.39, 29.31, 29.17, 22.79, 14.23.

5-n-Octylthiophene-2-carbonyl chloride (0C

). 13 C NMR (75 MHz, CDCl3): δC = 160. 77, 159.41, 138.78, 134.13, 126.47, 31.92, 31.32, 31.01, 29.32, 29.26, 29.11, 22.76, 14.20. 154.78, 128.64, 116.32, 114.83, 55.44. 36, 151.69, 129.60, 128.74, 125.43, 122.67, 116.49, 114.58, 55.58, 31.95, 31.58, 30.36, 29.39, 29.31, 29.15, 22.77, 14.22. .49-1.39 (2H, m), 1.39-1.26 (10H, m). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (100 MHz, CDCl3): δC = 153. 81, 153.46, 143.37, 128.41, 125.15, 119.89, 115.59, 114.76, 68.81, 55.88, 30.69, 30.42, 29.69, 29.64, 29.58, 29.54, 29.46, 26.20.

5-(4-Methoxy-phenyl)-2-h-tetrazole (0D

2-(4-Methoxy

2-(4-

3-(10-Bromodecyl)thiophene (1C).

A mixture of HBr (4 mL, 48 wt%, 36 mmol) and acetic anhydride (5.6 mL, 60 mmol) was added under argon to 3-(10-(4-Methoxyphenoxy)decyl)thiophene (1.82 g, 6 mmol), and the reaction mixture was heated to 100 o C for 24 h. After dilution with water, the mixture was extracted three times with diethyl ether. The combined organic phases were washed with saturated NaHCO3 solution until pH neutrality. After adding petroleum ether, the solution was settled overnight for hydroquinone precipitating completely. The solution was then filtered and submitted to a short silica gel column with petroleum ether as the eluant. Colorless oil was obtained after removing the solvent (Yield: 0.82 g, 45%). 1 H NMR (400 MHz, CDCl3): δH = 7.24 (1 Harom, dd, J = 4.9 Hz, J = 2.9 Hz), 6.95-6.22 (2Harom, m), 3.41 (2H, t, J = 6.9 Hz, -CH2-Br), 2.63 (2H, t, J = 7.7 Hz, -CH2-Ar), 1.86 (2Haliph, m), 1.63 (2Haliph, m), 1.40-1.25 (12Haliph, m). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (100 MHz, CDCl3): δC = 143. 32, 128.39, 125.15, 119.89, 34.15, 32.97, 30.67, 30.40, 29.58, 29.54, 29.42, 28.88, 28.30.

2,5-Dibromo-3-(10-bromodecyl)thiophene (1D). 3-(10-Bromodecyl)thiophene (1C) (1.14 g, 2.7 x 10 -3 mol) and N-Bromosuccinimide (1.06 g, 5.9 x 10 -3 mol) were dissolved in the mixture of 5 mL dry THF and 5 mL acetic acid. After stirring the reaction mixture at room temperature for 24 h, the reaction mixture was poured into cold water (15 mL) and extracted with diethyl ether (3 x 15 mL). The water (3 x 100 mL), dried over anhydrous MgSO4, and concentrated under reduced pressure. The crude product was precipitated using methanol (50 mL) and the resulting solid was washed through a Soxhlet thimble. The crude product was submitted to semipreparative SEC, using chloroform as the eluant, the solution was collected in thirty bottles. A purple powder was obtained (Yield: 191 mg, 66 %). SEC: Mn = 1. ). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CDCl3) δC = 153. 81, 153.46, 142.09, 128.37, 125.27, 115.58, 114.76, 108.93, 77.16, 68.82, 55.89, 30.43, 29.85, 29.68, 29.61, 29.54, 29.33, 26.20. The filtrate was washed with saturated NH4Cl solution (250 mL), water (3 x 150 mL) and then dried over anhydrous MgSO4. The solvent was removed by evaporator and the reddish crude product was further purified by column chromatography (PE:DCM =1:1, silica gel) as white solid (Yield: 1.05 g,

The dark-red precipitate was filtered, purified by Soxhlet extraction with acetone, pentane, and methanol (each 24 h). The polymer was then dissolved in chlorobenzene and precipitated from a warm solution of methanol to lead to a dark-red solid (Yield: 81mg, 90%). SEC: Mn,SEC = 1.5 x 10 4 , Mw/Mn = 1.6. (m, 4H), 1.70 (m, 4H), 1.44-1.32 (m, 24H).

PBTTT-Tri. 2,3,6,7,10-Penta(pentyloxy)-11-hydroxytriphenylene (81 mg, 0.12 mmol), K2CO3 (33 mg, 0.24 mmol) were dissolved in 30 mL DMF under argon. After 30 minutes, a solution of PBTTT-Br (22.3 mg, 0.03 mmol) in THF (3 mL) was added to the mixture. The resulting purple solution was stirred at 150 o C for 3 days, before being extracted at room temperature with chloroform (3 x 50 mL).

The organic layer was successively washed with water (3 x 50 mL), dried over anhydrous MgSO4, and concentrated under reduced pressure. The crude product was precipitated using methanol (60 mL) and the resulting solid was washed through a Soxhlet thimble. The crude product was submitted to semipreparative SEC, using chloroform as the eluant, the solution was collected in thirty bottles. A purple powder was obtained (Yield: 45 mg, 80%). SEC: Mn = 2.0 x 10 4 , Mw/Mn = 1.5. 70.11, 30.92, 29.82, 29.42, 28.60, 22.72, 14.19. Calculate for elemental analysis C: 74.72; H: 8.67; O: 9.95; S: 6.65; found: C: 70.96; H: 8.49; O: 8.43; S: 6.37.

3,6-Dibromo-9H-carbazole (2A).

A solution of N-bromosuccinimide (NBS, 22.35 g, 0.125 mol) in 50 mL of DMF was slowly with stirring added into a solution of carbazole (10 g, 0.167 mol) in 20 mL of DMF with an ice bath. After reacting for 4 hours, the reaction mixture was poured into 600 mL of ice water. After filtration, the collected mixture was purified from recrystallization in a mixture of EtOH and H2O (Yield: 76%). 1 H NMR (400 MHz,CDCl3) δ 8.08,8.04,7.48,7.46,7.24,7.21. 13 C NMR (101 MHz, CDCl3) δ 138. 36, 129.32, 124.11, 123.27, 112.65, 112.22. with water and dried over anhydrous MgSO4. After filtration and evaporation, the obtained crude was purified by column chromatography (eluent: PE:EA=5:1) and a transparent viscous liquid was eventually collected (Yield: 2.9 g, 53%). 1 H NMR (300 MHz, CD2Cl2) δ 8. 20, 7.59, 7.36, 5.36, 4.15, 2.11, 1.57, 1.23, 0.89. Pd(dppf)2Cl2 (439 mg, 0.6 mmol) was added into above solution under argon atmosphere. After freeze-pump-thaw for three times, the mixture was sealed and heated under Ar at 85 o C for 24 h. After cooling down, ethyl acetate was added and the resulting solution was washed with water and dried over anhydrous MgSO4. After filtration and evaporation, the crude product was further purified using silica gel chromatography (eluent: PE: EA =10:1) to give a yellow solid (yield: 559 mg, 29%). R = R2: Hz), 4.33 (d, J = 7.75 Hz), 2.76 (m, 1H), 1.38 (s, 28H), 1.17 (m, 16H), 0.86 (m, 8H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR ( 101MHz, Acetone) δ = 144. 02, 132.92, 128.13, 123.27, 109.77, 84.24, 32.57, 32.43, 29.84, 27.22, 27.15, 25.31, 23.29, 23.23, 14.33.

2-Chloroisophthalonitrile (2D

). 2-Chloroisophthalonitrile (2D) was prepared referring to the literature 272 . Preparation of LDA: Anhydrous diisopropylamine (6,6 mL, 46.82 mmol) was dissolved in 100 mL of anhydrous THF under argon and the solution was cooled down to -78 o C. n-BuLi (2,5M in hexane) (19 mL, 46.82 mmol) was added dropwise and the solution was stirred for 30 min at this temperature. A solution of isophthalonitrile (5 g, 39.02 mmol) in anhydrous THF (100 mL) was added dropwise at -95 o C into the above LDA solution and the resulting solution was stirred for 1 h.

Hexachloroethane (14.8 g, 62.44 mmol) dissolved in anhydrous THF (150 mL) was added to the reaction mixture at this temperature and the mixture was allowed to be stirred for 1 h. Then the mixture was warmed to room temperature and stirred for another 24 h. the reaction was quenched by adding a saturated ammonium chloride solution. The product was extracted by diethyl ether, washed with water and brine sequentially, dried over anhydrous MgSO4, and solvent removed under vacuum.

The product was purified by flash column chromatography (petroleum: diethyl ether = 4:1) and isolated as a pale yellow solid (Yield: 6.35 g, 51%). 1 H NMR (300 MHz, CDCl3): 7.85 (2H, d, J = 7.9

Hz), 7.48 (1H, t, J =7.9 Hz) 81, 8.44, 8.36, 7.95, 7.59, 7.11. of acridine rings and carbazole units in the backbone. The procedure of the polymerization is as follows: monomers dissolved in THF, and K2CO3 aqueous solution (2M) were mixed. Then, Pd(PPh3)4

was added with keeping the argon flowing. After freeze-pump-thaw cycling for three times, the mixture was sealed and heated at 85 o C for 3 days. Later, bromobenzene (2 mol equiv.) was added and the mixture was heated again at 85 o C for 24 h. After that, phenyl boron (2 mol equiv.) was added and the mixture was heated at 85 o C for another 24 h. After cooling down, the mixture was precipitated in acetone at 0 o C for three times. A final pure yellow solid was collected with a yield of 28-40%. The reaction was stirred for 24h at room temperature. The yellow solution was then extracted with methylene chloride (CH2Cl2). The organic phase was washed with water and dried over anhydrous MgSO4. The crude product was obtained via removing solvent and subsequently purified by silica gel column chromatography (eluent: toluene) to give a white powder (Yield: 1.3 g, 90%). 1 H NMR (400 MHz, CDCl3) δ = 8.17 (d, J = 7.8 Hz, 2H), 7.66 (d, J = 8.4 Hz, 2H), 7.56 (d, J = 8.4 Hz, 2H), 7.43 (m, 4H), 7.30 (m, 2H), 6.84 (dd, J = 17.6, 10.9 Hz, 1H), 5.89 (d, J = 17.6 Hz, 1H), 5.39 (d, J = 10.9 Hz, 1H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CDCl3) δ = 140. [START_REF] Long | Electron-Transporting Polymers Based on a Double B←N Bridged Bipyridine (BNBP) Unit[END_REF]137.26,136.89,136.15,127.74,127.26,126.09,123.56,120.45,120.11,114.87,109.95. 1 H NMR (400 MHz,CD2Cl2) δ = 8.17 (d,J = 7.81 Hz,2H),7.69(d,J = 8.38 Hz,2H),7.56(d,J = 8.38 Hz,2H),4H),2H),6.88 (dd,J = 10.87,17.69 Hz,1H),5.91 (d,J = 17.65 Hz,1H),5.39 (d,J = 10.93 Hz,1H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CD2Cl2) δ = 141. 23, 137.48, 137.20, 136.40, 127.99, 127.43, 126.38, 123.76, 120.61, 120.36, 114.92, 110.20, 53.84. 7.93, 7.22, 7.13, 6.95, 2.35, 2.20, 1.81, 1.52.

2-Bromobenzene

10-(4-ethenylphenyl)-9,9-dimethyl-9,10-dihydroacridine (5A). The mixture of 9,9-dimethyl-9,10dihydroacridine (2.09 g, 10 mmol), 1-bromo-4-vinylbenzene (2.20 g, 12 mmol), sodium tert-butoxide (1.92 g, 20 mmol), Pd2(dba)3 (183 mg, 0.2 mmol), and P(t-Bu)3/HBF4 (232 mg, 0.8 mmol) was stirred in 100 mL of dry toluene. After three freeze-thawing cycles, the mixture was heated at 110 o C for 18 h.

After cooling down to room temperature, the crude was extracted with CHCl3 and the organic phases washed with brine, before drying them by adding anhydrous MgSO4. After removing the solvents, a final silica gel column chromatography (eluent: PE/DCM = 4/1) allowed to isolate the product as a white powder (Yield: 2 g, 65%). 1 H NMR (400 MHz,CDCl3) δ = 7.68 (d,J = 8.26 Hz,2H),7.47 (d,J = 7.56Hz,2H),7.31 (d,J = 8.30 Hz,2H),6.95 (m,4H),6.83 (dd,1H),6.32 (d,2H),5.89 (d,1H),5.39 (d,1H), 1.70 (s, 6H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CDCl3) δ = 141.01, 140. 81, 137.62, 136.22, 131.55, 130.14, 128.72, 126.49, 125.36, 120.68, 115.11, 114.17, 36.11, 31.41 1.68(s, 6H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CD2Cl2) δ = 141. 32, 141.12, 137.97, 136.47, 131.77, 130.51, 128.97, 126.70, 125.60, 120.93, 115.18, 114.42, 36.33, 31.44. The reaction mixture was filtered hot through a 5 cm plug of Celite, before to be washedwith water, brine. After drying over anhydrous MgSO4, filtration and removing of the solvent, the crude product was further purified by silica gel column chromatography (eluent: toluene) to give a yellow powder polymers can be calculated according the following equations and the results are recorded in Table S1. xt value is calculated from the feed ratio; a x value calculated according to the C:H ratio of EA results; As we all know, in radical polymerization, AIBN serves as an initiator to decompose, eliminating a molecule of nitrogen gas to form two 2-cyanoprop-2-yl radicals, which initiate the polymerization.

2-(4-Vinylphenyl

Therefore, every polymer chain involves one 2-cyanoprop-2-yl end group with the formula of C4H6N, regardless of the length of polymers chains. For S3-991, the x values can't be calculated correctly, mainly because the existence of 2-cyanoprop-2-yl unit affects strongly the composition of polymers.

Corresponding to the number-average molecular weight (Mn,SEC = 1.8 x 10 4 ), the average degree of polymerization (Xn,SEC) of S3-991 is around 67, therefore, theoretically, 4A:4E:2-cyanoprop-2-yl unit = 99:1:1.5. The content of 4E and 2-cyanoprop-2-yl unit is so close to each other, so 2-cyanoprop-2-yl unit can't be ignored when doing the calculation. Strictly speaking, the DP value is attributed to absolute number-average molecular weight (Mn), which is different from the relative number-average molecular weight (Mn,SEC) obtained in SEC measurements. That's why here we can't give the x values.

Section 3.5: S4 polymers

The formula of 5A and 5B are C23H21N and C13H9N3, so the real composition can be calculated by the following equations.

, , xt value is calculated from the feed ratio; a x value calculated according to the C:H ratio of EA results; b x value calculated according to the C:N ratio of EA results; c x value calculated according to the H:N ratio of EA results; d xEA value is the average of x b and x c . These data were calculated on the condition of only considering repeating units.

Résumé en français

Après la découverte de la propriété de conductivité du polyacétylène par A. J. Heeger, A. G. • L'incorporation de substituants attracteurs d'électrons sur la périphérie des systèmes  peut améliorer la stabilité à l'oxydation de ces structures organiques tout en augmentant l'affinité électronique.

• Le remplacement d'éléments (en particulier les éléments de pontage au sein du système ) s'avère également efficace pour modifier la structure électronique et influencer l'empilement dans le matériau.

• Enfin, l'utilisation de noyaux aromatique fusionnés donc plus rigides pour générer des systèmes aromatiques polycycliques, peut modifier les énergies des orbitales frontières et moduler/réduire la bande interdite.

Au cours de ce travail de thèse, ces stratégies ont toutes été utilisées, en conjonction avec un couplage croisé pour créer une large gamme de polymères conjugués.

Plus précisément, nous nous sommes intéressés au design, à la synthèse et à la caractérisation de nouveaux polymères π -conjugués spécialement imaginés pour des applications en OFET et en OLED.

• Un premier objectif a été de préparer deux polymères π-conjugués liquide-cristallins à groupes pendants, nommés Polythiophene-oxa et PBTTT-Tri, qui peuvent s'autoorganiser en nanostructures ordonnées et qui présentent une conduction de type p (transporteur de trous).

•

Figure 1 . 1

 11 Figure 1. 1 The chemical structures of cis-/trans-polyacetylene, PPP, and PPV.

Figure 1 . 2

 12 Figure 1. 2 Diagram displaying the effect of decreasing bandgap between HOMO and LUMO as conjugation length increases, ultimately resembling the band-like structure observed within inorganic semiconductors.

Figure 1 . 4

 14 Figure 1. 4 Absorption spectra of dihexylfluorene (ODHF) oligomers with increasing length compared to poly(dihexylfluorene) (PDHF) showing the red-shifting effect of increasing conjugation length.[START_REF] Klaerner | Polyfluorene Derivatives: Effective Conjugation Lengths from Well-Defined Oligomers[END_REF]

Figure 1 .

 1 Figure 1. 5 a) DFT calculations of HOMO-LUMO energy levels for polyheteroles; 11 b) PCE vs hole mobility of S, Se, Te-containing polymers. 26

Figure 1 . 6

 16 Figure 1. 6 Aromatic and quinoid forms of polyphenylene, polythiophene, and polyisothianaphthene.

Figure 1 . 7

 17 Figure 1. 7 The two conjugations existing in poly(3-methylthiophene) and torsion in PEDOT.

Figure 1 . 8

 18 Figure 1. 8 Orbital mixing diagram showing the effect of reduced bandgap (Eg) achieved when bonding an electron-rich moiety (donor) with an electron-poor moiety (acceptor).

Figure 1 . 9

 19 Figure 1. 9 Examples of common side-chain motifs found in conjugated polymer systems.

  Impact on morphology, structure, and optoelectronics. Aside from solubility, side chains can also have a great influence on the solid-state morphology, structure as well as optoelectronic properties, with evidence of the addition of side chains on poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) increasing the backbone torsion along with affecting electron delocalization, 32 as shown in Figure 1. 10.

Figure 1 . 10

 110 Figure1. 10 Schematic explanation for the impact of side chains on the morphology and the electronic structure.[START_REF] Meyer | Side-Chain Engineering of Conjugated Polymers: Distinguishing Its Impact on Film Morphology and Electronic Structure[END_REF]

Figure 1 .

 1 Figure 1. 11 Traditional C-C coupling techniques for the preparation of π-conjugated backbones.[START_REF] Xu | Pd-and Ni-Catalyzed Cross-Coupling Reactions in the Synthesis of Organic Electronic Materials[END_REF]

Scheme 1 . 1

 11 Scheme 1. 1 The synthetic route of Stille cross-coupling.

Scheme 1 . 2 AScheme 1 . 3

 1213 Scheme 1. 2 A general mechanism for Stille coupling.

  Scheme 1. 4 A general mechanism for Suzuki coupling.

Scheme 1 . 6

 16 Scheme 1. 6 Proposed mechanism of GRIM method for the synthesis of regioregular P3AT.

Figure 2 . 1 . 1

 211 Figure 2.1. 1 OFETs structures 75 : a) top-gate bottom-contact (TGBC); b) top-gate top-contact (TGTC); c) bottom-gate top-contact (BGTC); d) bottom-gate bottom-contact (BGBC).

  Figure 2.1. 2 shows the typical output and transfer characteristics for p-type and n-type transistors, where the effect of VG and VSD is clear.

Figure 2 . 1 . 2

 212 Figure 2.1. 2 The structures of p-type, n-type, and ambipolar OFET devices. Output characteristics for p-type (a) and n-type (b) transistors; Transfer characteristics for p-type (c) and n-type (d) transistors.[START_REF] Wang | Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer[END_REF]

  Where and are the current and voltage bias between the source (S) and the drain (D) electrodes, respectively; is the gate voltage applied between the gate (G) and the source (S) electrodes, producing charges in the channel because of the electrostatic effect; is the threshold voltage at which the current starts to rise, C is the capacitance of the gate dielectric, W and L are the width and length of the conducting channel, respectively.

Figure 2 . 1 . 3

 213 Figure 2.1. 3 Influence of organization degree on charge transport properties.

Figure 2 . 1 . 4

 214 Figure 2.1. 4 D-A polymers for p-type OFETs 3 : (A) Common acceptors; (B) Common donors; (C) High-performance p-type polymers.

Figure 2 . 1 . 5 F

 215 Figure 2.1. 5 F-substituted polymers for ambipolar or n-type OFETs.[START_REF] Zheng | Strong Electron-Deficient Polymers Lead to High Electron Mobility in Air and Their Morphology-Dependent Transport Behaviors[END_REF][START_REF] Bura | New Fluorinated Dithienyldiketopyrrolopyrrole Monomers and Polymers for Organic Electronics[END_REF]

Figure 2 . 1 . 6 N

 216 Figure 2.1. 6 N-substituted polymers for ambipolar or n-type OFETs.[START_REF] Xiao | High Performance Polymer Nanowire Field-Effect Transistors with Distinct Molecular Orientations[END_REF][START_REF] Fu | Molecular Engineering of Nonhalogenated Solution-Processable Bithiazole-Based Electron-Transport Polymeric Semiconductors[END_REF]

Figure 2 . 1 . 9 B

 219 Figure 2.1. 9 B-substituted polymers for ambipolar or n-type OFETs.[START_REF] Long | Electron-Transporting Polymers Based on a Double B←N Bridged Bipyridine (BNBP) Unit[END_REF]

Figure 2 . 1 . 10

 2110 Figure 2.1. 10 Molecular structures of D-A and acceptor dimerization polymers.

Figure 2 . 1 . 11

 2111 Figure 2.1. 11 Reported ambipolar or n-type polymers by the acceptor dimerization strategy.[START_REF] Zhu | Regioregular Bis-Pyridal[2,1,3]Thiadiazole-Based Semiconducting Polymer for High-Performance Ambipolar Transistors[END_REF]100

Figure 2 . 1 .

 21 12 shows the molecular structures of reported polymers by sidechain engineering strategy for ambipolar or n-type OFETs. Such side chains include siloxanesolubilizing chains 101 and semifluoroalkyl chains 102 , among others. Note that this strategy can also be applied to other high-performance polymers to further improve their performance.

Figure 2 . 1 . 12

 2112 Figure 2.1. 12 Ambipolar or n-type polymers by side-chain engineering. 101-103

2. 1 . 4

 14 Liquid crystalsDiscovery. Liquid crystalline materials were first discovered in cholesteryl ester by Friedrich Reinitzer in 1888.104 The main discoveries of Reinitzer were high levels of optical activity and dual melting points in his samples. The samples were sent to Prof. Lehmann to perform systematic microscopy studies: he published two major findings on properties unique to liquid crystalline materials: anisotropy and fluidity. Consequently, Lehmann coined the word "liquid crystal". Then, Pierre-Gilles de Gennes, a French physicist, advanced many theoretical studies on liquid crystalline materials and received a Physics Nobel Prize in 1991. In the present era, enthusiasm in liquid crystalline materials research stems from two sources: understanding novel liquid crystalline phases and the development of large-scale flexible electronics.2.1.4.1 LC phases and nanostructuresToday, liquid crystalline (LC) materials are omnipresent in all aspects of life. They are found almost everywhere: from self-assembling biological DNA to the working material of various display technologies. Liquid crystalline materials are a special phase of matter with the unique property of self-organization or self-assembly due to attractive van der Waals forces between individual molecules.105 The liquid crystal phase exists between an isotropic liquid phase and a crystalline solid phase.106 According to the formation condition of LC phase, liquid crystals are also divided into thermotropic and lyotropic phases, depending on the fact that phase transitions are observed due to temperature changes or under appropriate concentration and pressure, respectively.Liquid crystalline molecules share many mechanical properties of liquids, such as high fluidity, as well as formation and coalescence of droplets. At the same time, liquid crystalline materials are similar to crystalline solid such that they exhibit electrical, mechanical, optical, and magnetic anisotropy. In short, liquid crystalline materials flow like liquids, while maintaining partial orientational and positional ordering like solids(Figure 2.1. 13).

Figure 2 . 1 . 13

 2113 Figure 2.1. 13 Mobility and order in liquid crystals and mesophases 107 .

Figure 2 . 1 . 14

 2114 Figure 2.1. 14 The formation of mesophases.

Figure 2 . 1 . 15

 2115 Figure 2.1. 15 The electronic properties of lamellar and columnar mesophases.

Figure 2 . 1 .

 21 Figure 2.1. 16 Side-chain and main-chain LC polymers (with 2 examples of chemical structures).

Figure 2 . 1 . 17

 2117 Figure 2.1. 17 Basic types of ordering in LC polymers for main-chain and side-chain LC polymers. 113

Figure 2 . 1 . 18

 2118 Figure 2.1. 18 Birefringent texture observed under POM for one sample at room temperature and the mosaic texture observed upon cooling from the isotropic phase. 114

Figure 2 . 1 .

 21 Figure 2.1. 19 DSC thermograms obtained for one sample 114 showing phase transitions during heating and cooling cycles at a scan rate of 5 °C•min -1 .

Figure 2 . 1 . 3

 213 Figure 2.1. 20 a) The principle of XRD; b) Typical XRD pattern of a columnar mesophase presenting Bragg's reflections of the columnar organization. 115

Figure 2 . 1 .

 21 Figure 2.1. 21 Ph-BTBT-10 116 : (a) Chemical structure; (b) POM texture observed at 150 °C, the white bar indicates a scale of 50 μm; (c) XRD pattern of a liquid crystalline film exhibiting a polydomain texture acquired at 160 °C in an out-of-plane configuration; (d) DSC curves obtained on heating and cooling at 2 °C min -1 and single-crystal structures of the (e) ac and (f) ab planes.

Figure 2 . 1 . 22 1 s - 1 Figure 2 . 1 . 23

 2122112123 Figure 2.1. 22 Schematic representation of (a) poly(3-alkylthiophene) and (b) its organization. 128

Figure 2 . 1 .

 21 Figure 2.1. 24 (a) Chemical structure of calamitic side-chain LC polymer, with poly(phenylene) as backbone and cyanoterphenyl as calamitic side chain part and (b) proposed SmA lamellar arrangement for the polymer. 131

Figure 2 . 1 . 25

 2125 Figure 2.1. 25 Structure of regioregular poly(3-hexylthiophene): (a) orientation of lamellae; (b) common (high temperature) form; (c) metastable interdigitated polymorph.

Figure 2 . 1 .

 21 Figure 2.1. 26 a) General synthetic route for the preparation of triphenylene side-chain homopolymers PTmT with different lengths of the aliphatic spacer. b) Schematic view of the lamello-columnar structure of PT10T consisting in the alternation of triple rows of triphenylene columns and the polythiophene sub-layers, arranged in a rectangular p2gg lattice involving twelve columns and two sub-layers (white frame). c) Topography AFM image of PTmT nanostructured thin film on a silanized silicon wafer and terrace step profile determined from topography. d) Typical transfer characteristic of a top-contact bottom-gate OFET based on PTmT polymers (PT10T).147,148

Figure 2 . 1 .

 21 Figure 2.1. 27 a) Chemical structures of the target donor-acceptor polymers; b) Schematic representation of the lamello-lamellar structure consisting in the alternation of double sub-layers of perylene moieties and of polythiophene sub-layers. (Yiming's thesis) 150

Figure 2 . 1 . 28

 2128 Figure 2.1. 28 Target polymer chemical structures designed for OFET applications (chapter 2)

  specifically, the target polymer, namely, Polythiophene-oxa, is composed of a regioregular poly(3decylthiophene) as the backbone and calamitic-type electron-acceptor oxadiazole entities, i.e. 2-(4decyloxy-phenyl)-5-(5-octyl-thiophene-2-yl)-[1,3,4]oxadiazole, as side groups (Figure 2.2. 1).

Figure 2 . 2 . 1

 221 Figure 2.2. 1 (a) Schematic representation and (b) chemical structure of the target polymer Polythiophene-oxa.

Scheme 2 . 2 . 4

 224 Scheme 2.2. 4 Synthetic pathway of Polythiophene-oxa.

Figure 2 .

 2 Figure 2.2.2 1 H NMR spectra of Polythiophene-Br (top) and Polythiophene-oxa (bottom).

  40 °C and polystyrene (PS) as the calibration standard. As the polythiophene have a quite different hydrodynamic volume in THF with that of PS, the relative number-average molecular weight (Mn,SEC) of regioregular poly(3-alkylthiophene) obtained from SEC measurements is usually 1.5-2 folds of the absolute number-average molecular weight (Mn,NMR) calculated from the NMR spectra.153Polythiophene-Br exhibit the relative number-average molecular weight (Mn,SEC = 1.03 x 10 4 ) with narrow dispersity (Mw/Mn = 1.22), giving the number of repeating units (Xn,SEC) of 34, which is in close agreement with the absolute value calculated from the NMR spectra (Xn,NMR = 20, Xn,SEC/Xn,NMR = 1.7). The narrow dispersity indicates that Polythiophene-Br may achieve well-defined polymeric architecture. After the substitution, the SEC curve shifted to the region of higher molecular weight(Figure 3.2. 3). The target Polythiophene-oxa have the relative number-average molecular weight (Mn,SEC = 1.8 x 10 4 ) with narrow dispersity (Mw/Mn = 1.47), giving the number of repeating units (Xn,SEC) of 31, also in agreement with the NMR results (Xn,NMR = 18, Xn,SEC/Xn,NMR = 1.7). The summary of the polymer characteristics is given in Table2.2. 1.

Figure 2 . 2 . 3

 223 Figure 2.2. 3 SEC curves of Polythiophene-Br and Polythiophene-oxa in THF (Polystyrene as calibration standard).

Figure 2 . 2 . 4

 224 Figure 2.2.4 (a) POM image and (b) DSC thermogram of Polythiophene-oxa.

Figure 2 . 2 . 5

 225 Figure 2.2.5 (a) The XRD pattern and (b) schematic representation of the Polythiophene-oxa selforganization and illustration of preferential orientation on substrate.

Figure 2 . 2 . 6

 226 Figure 2.2. 6 The output (left) and transfer (right) characteristics of a top-contact bottom-gate OFET based on Polythiophene-oxa after annealed at 120 o C for 2h.

  conjugated polymers, which are expected to exhibit liquid-crystalline properties. More precisely, the new two polymers were designed to comprise poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2b]thiophene) (PBTTT) as the backbone and either the discotic-type monohydroxy triphenylene derivative or the calamitic-type 2-(4-decyloxy-phenyl)-5-(5-octyl-thiophene-2-yl)-[1,3,4]oxadiazole (0F) as the side groups (Figure 2.3. 1).

Figure 2 . 3 . 1

 231 Figure 2.3. 1 Chemical structures of desired new side-chain π-conjugated polymers PBTTT-Tri and PBTTT-oxa.

Scheme 2 . 3 . 3

 233 Scheme 2.3. 3 Synthetic route towards liquid-crystalline semiconducting polymer PBTTT-Tri.

1. 5 ,

 5 giving the value of Xn,SEC of 10, much small than that of PBTTT-Br. Similar to poly(3- alkylthiophene), no matter PBTTT-Br or PBTTT-Tri has a rigid conjugated backbone, quite different from the calibration standard polystyrene (PS). Therefore, the values of Xn,SEC obtained from SEC measurements have a big difference from the realistic values.

Figure 2 .

 2 Figure 2.3. 2 1 H NMR spectra of PBTTT-Br (top) and PBTTT-Tri (bottom) in CDCl3 at 50 °C.

Figure 2 . 3 . 3

 233 Figure 2.3. 3 SEC curves of PBTTT-Br and PBTTT-Tri.

  texture. Nevertheless, a birefringent viscous phase was observed by POM at room temperature, revealing the existence of an anisotropic medium (Figure2.3. 4 a). On heating to 100 o C, the viscous phase transformed progressively into a non-birefringent isotropic phase. Then on cooling from the previous isotropic state to room temperature, no birefringence was observed, indicating its amorphous character.

Figure 2 . 3 . 4

 234 Figure 2.3. 4 (a) POM image of PBTTT-Tri at room temperature; (b) DSC thermograms of PBTTT-Tri on heating and cooling at a rate of 20 o C/min.

Figure 2 . 3 . 5 Figure 2 . 3 . 6

 235236 Figure 2.3. 5 SAXS patterns of PBTTT-Tri in pristine state (a) and after annealed at 80 o C (b).

Figure 2 . 3 . 7

 237 Figure 2.3. 7 Schematic representation of the PBTTT-Tri self-organization and illustration of preferential orientation on substrate.

Figure 2 . 3 . 8

 238 Figure 2.3. 8 Output and transfer characteristics of a top-contact bottom gate OFET based on PBTTT-Tri after annealed at 50 o C for 15 min and 60 o C for another 15 min.

3. 1 . 1 A

 11 brief introduction to organic light-emitting diodes (OLEDs) Organic light-emitting diodes (OLEDs) are now at the stage of commercialization since the pioneering work of the first organic electroluminescent diode based on a fluorescent material in the 1980s.154 OLEDs are a promising alternative to LCDs and are one of the most important potential candidates for displays and lightening sources.* Work principle and structural architecture of OLED devicesAs depicted in Figure3.1. 1, every OLED device has an anode and a cathode for the charge injection, at least one electrode being transparent. Normally, transparent conducting oxide films such as ITO are used as anodes due to their high work function for hole injection, whereas metals with low work function, particularly aluminum (Al), are good candidates for cathodes. During the last several decades, the OLED devices have developed from monolayer to multilayer structures across three generations of organic light-emitting materials as dopants.

Figure 3 . 1 . 1

 311 Figure 3.1. 1 (a) monolayer OLED device; (b) multilayer OLED device.

Figure 3 . 1 . 2

 312 Figure 3.1. 2 Spin statistics 156 : the recombination with spins and phases in two potential directions, producing four excitons, including one singlet exciton and three triplet excitons. 157

Figure 3 . 1 . 3

 313 Figure 3.1. 3 Schematic diagram outlining the importance of the film density, molecular orientation, and transition temperature of amorphous organic semiconductor films in OLEDs.

Figure 3 . 1 . 4

 314 Figure 3.1. 4 Schematic illustration for the emission mechanism of FOLEDs and PhOLEDs.

Figure 3 . 1 . 5 Figure 3 . 1 . 6

 315316 Figure 3.1. 5 Schematic illustrations for the emission mechanism of TADF molecules.

Figure 3 . 1 . 7

 317 Figure 3.1. 7 Chemical structures of representative donors and acceptors. 177

Figure 3 . 1 . 8

 318 Figure 3.1. 8 The chemical structures of 4CzIPN, DCzIPN, and DDCzIPN.

( 4 -Figure 3 . 1 . 9 )

 4319 Figure 3.1. 9) exhibited three times longer lifetime than the current TADF emitters, as the weak C-N bond was stabilized by a small dihedral angle between donor and an aromatic linker. 188 Besides, TADF materials should also have good thermal stability, as OLED devices give rise to heat during the operation.

Figure 3 . 1 . 9 191 Figure 3 . 1 . 10

 3191913110 Figure 3.1. 9 The chemical structure of TCzIPN

Figure 3 . 1 .

 31 Figure 3.1. 11 UV-vis and PL spectra of TICNBI in various solutions and neat films. 166

  phosphorescence and PF are different. Based on this principle, TRES is considered as another technique to determine the source of the delayed components. Determination of ΔEST and ΔEa TADF . As stated above, ΔEST, the difference of the energy of the lowest singlet (ES1) and triplet (ET1) states, is the most important parameter in determining the lifetime of DF ( ) as well as DF/PF ratio ( ). The general requirement for ΔEST in designing TADF materials is less than 0.2 eV. From an experimental point of view, according to the photo energy formula (3.1.8), the value of ES1 and ET1 can be determined directly from onset or maximum of the prompt fluorescence and phosphorescence spectra, respectively. It is worth noting that it is necessary to observe phosphorescence at a very low temperature (< 20 K) when the ΔEST is lower than 0.01 eV, to ensure no delayed fluorescence occurs. (3.1.8)

Figure 3 . 1 . 12

 3112 Figure 3.1.12 Some examples of TADF small molecules with different emission colors.[198][199][200][201]

Figure 3 . 1 .

 31 Figure 3.1. 13 TADF dendrimers with conjugated (a) and non-conjugated (b) linkages.

(Figure 3 . 1 .

 31 14b), DMOC-DPS core and bipolar phosphine oxide carbazole (POCz) dendrons are connected by hexyl chains. The bipolar dendrons not only improve the morphological stability but also restrain the concentration quenching effect of the TADF core. The spin-coated OLEDs featuring POCz-DPS as the host-free emitter achieved a high EQEmax of 7.3% and higher color purity relative to those of devices based on DMOC-DPS.

Figure 3 . 1 .

 31 Figure 3.1. 14 TADF dendrimers with (a) conjugated 207 and (b) non-conjugated 208 linkages.

Figure 3 . 1 . 15

 3115 Figure 3.1. 15 The chemical structure of the first reported linear TADF polymer. 210

Figure 3 . 1 . 16

 3116 Figure 3.1. 16 Schematic representatives of linear conjugated TADF polymers (D: donor, A: acceptor, B: conjugated backbone, S: conjugated spacer).

Figure 3 . 1 .

 31 Figure 3.1. 17 TADF conjugated polymers with alternating donor and acceptor in the backbone (pCzBP and pAcBP, 212 PTCz and PTD 213 ).

Figure 3 . 1 . 18

 3118 Figure 3.1. 18 Chemical structures of linear conjugated polymers with pendant TADF units. 214

Figure 3 . 1 .

 31 Figure 3.1. 19 TADF polymers with acridine and carbazole as the electron-donating backbone.

  categories of conjugated TADF polymers with varying TADF content222 , named PCzA3PyBx, PCzAB2Pyx, PCzAB3Pyx, respectively(Figure 3.1. 19). All these polymers exhibited a small ΔEST of less than 0.2 eV. The PLQYs range of PCzA3PyBx, PCzAB2Pyx, and PCzAB3Pyx in neat films under nitrogen atmosphere are 15 47%, 23 68%, and 31 68%, respectively. PCzA3PyB50, PCzAB2Py50, and PCzAB3Py50 with 50 mol% TADF content produced yellow to orange emission with the longest EL wavelength in each group ( for PCzA3PyB50, for PCzAB2Py50, and for PCzAB3Py50). With decreasing TADF content in these polymers, the electroluminescent emission blueshift from green to yellow region PCzAB3Py5 possessed the best electroluminescent performance in each group, with external EQEs of 5.2%, 11.9%, and 12.2%, respectively. Besides TADF conjugated polymers with acridine/carbazole backbone, several TADF conjugated polymers (Figure 3.1. 20) were derived from yellow-emitting PTZ-DBTO2 223 . COPO2 223 is an alternating TADF conjugated copolymer exhibiting large efficiency roll-off with an EQEmax of 11.05% at 5.5 V. To improve its EL performance, alkyl chains were introduced into the polymers to provide solubility, and carbazole (Cz) or triphenylamine (TPAs) units serve as host units to tune TADF characteristics. Homo, Cop-50, and Cop-10 are homopolymer, alternating copolymer, and random copolymer, respectively. All these polymers had a ΔEST smaller than 0.1 eV, but their PLQYs are only 10%, 18%, and 21% in doped films in the air, as a result of the aggregation effect. The non-doped Cop-10-based solution-processed OLED device could reach an EQEmax of 15.7% with a low turn-on voltage of 3.2 V. 224 In PTDP-x, TPA is also a blue emitter. PTDP-5 and PTDP-10 exhibited a quite high PLQY close to 100% in doped films under nitrogen condition, and their ΔEST are 30 meV and 23 meV, respectively. As only the yellow emission from TADF units is affected by oxygen, the emission color is different in the presence and absence of oxygen. The PTDP-10-based doped solutionprocessed OLED achieved a 4.8% EQEmax with the CIE coordinates of (0.44, 0.43), while PTDP-5based OLED produced warm white emission with 7.1% EQEmax. 225

Figure 3 . 1 . 20

 3120 Figure 3.1. 20 Chemical structures of TADF polymers designed based on PTZ-DBTO2.

Figure 3 . 1 . 21

 3121 Figure 3.1. 21 Chemical structures of TADF polymers PFSOTTx.

Figure 3 . 1 . 22

 3122 Figure 3.1. 22 Polymers with twisted D/A backbone and pendant triazine derivate acceptor.

Figure 3 . 1 . 23

 3123 Figure 3.1. 23 Chemical structures of linear conjugated TADF homopolymers.

Figure 3 . 1 . 24

 3124 Figure 3.1. 24 Chemical structure of PCzDP-x. 214

  wavelength of luminescent emission in neat films; ΔEST is calculated from the equation ΔEST=ES-ET, where ES is obtained from the photoluminescent spectrum at room temperature, ET is from phosphorescent spectrum;is the total photoluminescent quantum efficiency (PLQY), is the quantum efficiency contributed by delayed fluorescence, is the lifetime of prompt fluorescence, is the lifetime of delayed fluorescence, , , , were measured in neat films free-oxygen; is the electroluminescent peak; Von is the turn-on voltage at 1 cd/m 2 ; Lmax is the maximum luminance; CE/PE/ EQE refer to maximum current efficiency, maximum power efficiency, and maximum external quantum efficiency, respectively; C.I.E is short of The Commission Internationale de L'Eclairage coordinates; C B, G, R, Y, and W are short for blue, green, red, yellow and white, respectively; GY is greenish-yellow and BG is bluishgreen. a Measured in toluene, b measured in blend film; c: measured at 10 cd/m 2 .

Figure 3 . 1 . 25

 3125 Figure 3.1. 25 Structural architectures of linear non-conjugated TADF polymers.

Figure 3 . 1 . 26

 3126 Figure 3.1. 26 Chemical structure of P(DMTRZ-Cp) with non-conjugated cyclohexane units.

Figure 3 . 1 . 28

 3128 Figure 3.1. 28 Chemical structures of non-conjugated TADF polymers: green (Px 237 ,VTDx 238 ) blue (PBD-x 239 and PDT-x 240 , red (PFDMPE-Rx and PCzDMPE-Rx 241,242 ).

Figure 3 . 1 . 29

 3129 Figure 3.1. 29 Chemical structures of through-space charge transfer TADF polymers.

  1. 29), 9,9-dimethyl-10-phenyl-acridine are chosen as the pendant donor unit, and triazine or triacrylboron derivates are selected as the pendant acceptors. Using triazine acceptors, P2-05 (also named P-Ac95-TRZ05 243 ) achieved a small ΔEST (0.021 eV) and a high neat film state PLQY of 51% under N2 at room temperature, and it exhibited sky-blue electroluminescent emission in a non-doped solution-processed device with a high EQEmax of 12.1% and low efficiency roll-off of 4.9% (at 1000 cd m -2 ), together with CIE coordinates of (0.176, 0.269). Based on P2-05, acceptors with different electron-accepting capabilities were selected to tune the TSCT strength between donor and acceptor. All these polymers featured aggregation-induced emission. The PLQYs of the polymer neat films are 29%, 51%, 74%, 34%, and 6%, respectively, for the polymers from P1-05 to P5-05, while those for P1-50, P2-50, and P3-50 ARE 32%, 60%, and 64%. The emission colors range from deep blue (P1Moreover, white emission was also realized by incorporating two donor/acceptor pairs in one polymer (WP-y) with simultaneous sky-blue and yellow emission.244 By adopting triarylboron acceptors, the resulting three groups of TSCT polymers (PH-x, PF-x, and PTF-x) 245 exhibited small ΔEST smaller than 0.2 eV. With the substituents changing from H to F and CF3, the polymers displayed deep-blue (429 nm) to sky-blue (483 nm) emission accompanied with the improved PLQY from 26 to 53% in the solid-state, due to the increment of the electron-accepting ability of triarylboron units. PTF-20 showed promising electroluminescent performance with an EQEmax of 7.0%, suggesting that they are prospective candidates for luminescent polymers.Besides, Hudson et al. described a miktoarm copolymer ACR75-co-TRZ75-BB, which can aggregate into bottlebrush nanofibers with homopolymer side chains and the through-space charge transfer (TSCT) arising from the resulting interfaces formed between donor and acceptor can give rise to thermally activated delayed fluorescence (TADF) along with the properties of original donor and acceptor components.246 The stimuli-responsive TADF character strongly relies on the aggregation of the nanofibers(Figure 3.1. 30). The bottlebrush nanostructure may prove to be an effective method for preparing blended, multi-components films for organic semiconductors, where maximizing D-A interactions or preserving the individual properties of each component of a blend may be necessary, for example, in organic photovoltaics or ambipolar films for charge transport.

Figure 3 . 1 .

 31 Figure 3.1. 30 TSCT polymers achieving TADF from interface-dependent aggregation.

  Moreover, TSC systems possess more flexibility and possibilities in designing optoelectronic materials with stable ICT states, because of its non-covalent structure and spatial delocalization of π electrons. To date, several other TSC systems have been exploited, derived from cyclophane 251 , hexaarylbenzene 252 , naphthalene 253 , xanthene 254 , and so on (Figure 3.1. 31).

Figure 3 . 1 .

 31 Figure 3.1. 31 TSC systems based on cyclophane, hexaarylbenzene, xanthene, and naphthanene.

  .1. 33) where a donor and an acceptor bridged by 9,9-dimethylxanthene are in close proximity to realize the efficient spatial charge transfer.254 These materials displayed obvious TADF nature as well as AIE behavior. The OLED device using XPT dispersing in DPEPO film as the emitter gave rise to electroluminance with a 10% EQEmax. The comparison between U-shaped and L-shaped D-A molecular structures (Figure3.1. 33) evidenced that the connection style between donor and acceptor moieties plays a crucial role in the CT character and .256 However, it is noteworthy controlling the bridge flexibility and avoiding intramolecular dimerization quenching, because the flexible bridge probably causes strong dipole-dipole attraction between donor and acceptor units, further resulting in large reorganization to form intramolecular dimer species, whose local triplet excited states are high enough to quench the RISC process and thus reduce delayed fluorescence.257

Figure 3 . 1 . 32

 3132 Figure 3.1. 32 Chemical structures of triptycene-based TADF materials.

Figure 3 . 1 . 33

 3133 Figure 3.1. 33 Chemical structures of conventional through-bond conjugated D-A (L-shaped) and through-space conjugated (U-shaped) architectures.

Figure 3 . 1 . 34

 3134 Figure 3.1. 34 Chemical structures of TSCT TADF materials based on cyclophane.

Figure 3 . 1 . 35

 3135 Figure 3.1. 35 Chemical structures of two blue through-space conjugated TADF materials.

Figure 3 . 1 . 36

 3136 Figure 3.1. 36 Chemical structures of the TSCT-HABs

Figure 3 . 1 . 37

 3137 Figure 3.1. 37 The chemical structures of the four series of S1, S2, S3, and S4 polymers

Figure 3 . 2 . 1 Figure 3 . 2 . 2

 321322 Figure 3.2.1 The molecular structure of 26IPNDCz with the calculated spatial distributions of HOMO and LUMO energy levels.

Figure 3 . 2 .

 32 Figure 3.2. 4 1 H NMR spectrum of 2E in THF.

Figure 3 . 2 .

 32 Figure 3.2. 5 1 H NMR spectrum of 2B(-R2) in CD2Cl2.

Figure 3 . 2 .

 32 Figure 3.2. 6 1 H NMR spectrum of 2C(-R2) in acetone.

Figure 3 . 2 . 7

 327 Figure 3.2.7 The 1 H NMR spectra of S1 polymers in CD2Cl2.

Figure 3 . 2 . 8

 328 Figure 3.2.8 The SEC curves of S1 polymers.

Figure 3 . 2 . 9

 329 Figure 3.2.9 The normalized UV-Vis absorption and PL spectra of S1 polymers in toluene.

Figure 3 . 2 . 10

 3210 Figure 3.2.10 The normalized UV-Vis absorption and PL spectra of S1 polymers in CHCl3.

Figure 3 . 2 . 11

 3211 Figure 3.2.11 The transient PL decay curves of S1 polymers in toluene.

2 . 3 .

 23 Among the polymers, S1-11 exhibits the emission with the shortest PF and the longest DF lifetimes, while S1-91 holds the longest PF and the shortest DF lifetimes. The values of PF lifetimes for S1-11, S1-11-L, and S1-91 are 33.4, 39.6, and 42.8 ns, respectively, and the DF lifetimes of the polymers are around 0.7-1.0 μs, which is rather short, indicative of a quick reverse intersystem crossing process.

2 . 4 .

 24 Figure 3.2.12 and the photophysical parameters are reported in Table 3.2.4. The absorption spectra show the main characteristic peaks (312, 307, and 315 nm for S1-11, S1-11-L, and S1-91, respectively), corresponding to the π-π transition. The optical energy gap of 2.60, 2.67, and 2.34 eV for S1-11, S1-11-L, and S1-91, respectively, were obtained from the onset of absorption. The PL spectra display broad CT emissions peaked at 529, 513, and 530 nm for S1-11, S1-11-L, and S1-91, respectively. The Stokes shift can be calculated in the neat film for S1-11, S1-11-L, and S1-91:

Figure 3 . 2 . 12

 3212 Figure 3.2.12 The normalized UV-Vis absorption and PL spectra of S1 polymers in the neat film.

  respectively (Figure 3.2.13). The ES values of S1-11, S1-11-L, and S1-91 are 2.86, 3.00, and 2.33 eV, and the ET values of S1-11, S1-11-L, and S1-91 are 2.85, 2.98, and 2.31 eV. Based on these later values, the ΔEST values of S1-11, S1-11-L, and S1-91 were calculated to be 0.01, 0.02, and 0.02 eV, respectively.

Figure 3 . 2 .

 32 Figure 3.2.13 Fluorescence (300K) and phosphorescence (17K) spectra of S1 polymers in neat film measured by a streak camera.

Figure 3 . 2 . 14

 3214 Figure 3.2.14 Photoelectron spectra of S1 polymers in neat film.

  time-resolved fluorescence spectroscopy with time-correlated single-photon counting (TCSPC) in both air and argon atmosphere(Figure 3.2.15). All the decay curves are composed of one PF and one DF components, indicating the TADF character of the polymers in neat film. Unfortunately, no real difference in decays is observed between the air and argon environment. This indicates that the simple flow of argon around the S1 polymer films is probably not enough to remove all the oxygen quenchers.The PF lifetimes of the polymers can be calculated from the mono-exponential function and the values of S1-11, S1-11-L, and S1-91 are 8.7, 7.3, and 13.6 ns, respectively. Besides, the delayed fluorescence can be fitted with a bi-exponential function. These very short DF lifetimes (Table3.2.6) are consistent with the very low PLQY and TADF activity of the S1 polymer series in neat films.

Figure 3 . 2 . 15

 3215 Figure 3.2.15 Fluorescence decays of S1 polymers in neat films at room temperature.

2 . 16 ,

 216 obvious prompt and delayed fluorescence components can be observed. We can note that under vacuum, The DF components of the different neat films are much longer than those studied previously by TCSPC equipment under a simple argon flow. This also indicates that the previous PLQYs in neat film determined under Ar flow are probably underestimated.

Figure 3 . 2 .

 32 Figure 3.2.16 Temperature-dependent transient PL decay curves of S1 polymers in neat film ranging from 100 to 300 K measured by a streak camera.

Figure 3 . 3 . 1

 331 Figure 3.3.1 The molecular structure and conformation of Pm5 with the calculated spatial distributions of HOMO and LUMO energy levels 266

Scheme 3 . 3 . 1

 331 Scheme 3.3.1 The synthetic route of S2 polymers. Conditions: 1) Pd2(dba)3, P(t-Bu)3/HBF4, t-BuONa, toluene, 110 o C, Ar, 18 h, 65% ;2) bis(pinacolato)diboron, Pd(OAc)2, Sphos, 1,4-dioxane, KOAc, 101 o C, 3 h, 52%; 3) 2-chloropyrimidine-5-carbonitrile, Pd(dppf)2Cl2, Cs2CO3, 1,4-dioxane/H2O, 52%; 4) NBS, DCM/DMF, dark, 77%; 5) Pd(PPh3)4, K2CO3, THF/H2O, 85 o C, 3 d, 28-40%.

Figure 3 . 3 . 2 1 H

 331 Figure 3.3. 2 1 H NMR spectrum of the monomer 3D in CD2Cl2.

Figure 3 .

 3 Figure 3.3.3 1 H NMR spectra of S2 polymers in CDCl3 (600MHz).

Figure 3 . 3 . 4

 334 Figure 3.3.4 SEC curves of S2 polymers.

Figure 3 . 3 . 5

 335 Figure 3.3.5 The normalized UV-vis absorption and PL spectra of S2 polymers in toluene.

Figure 3 . 3 . 6

 336 Figure 3.3.6 The normalized UV-vis absorption and PL spectra of S2 polymers in CHCl3.

Figure 3 . 3 . 7 ,

 337 Figure 3.3.7, the transient PL decay spectra in air and nitrogen atmosphere are given in Figure 3.3.7

Figure 3 . 3 . 7

 337 Figure 3.3.7 The transient PL decay spectra of S2 polymers in toluene.

  displays a shoulder around 342 nm, resulting from the extended conjugation of acridine rings concerning the 3,6-carbazole ring. However, in these spectra, the long-wavelength absorption of S2-11 and S2-31 corresponding to the CT band of TADF chromophores ( ) almost disappears, which is in adequation with the low PLQYs of S2-11 and S2-31 in neat films (Table 3.3.4). Furthermore, the optical energy gap of 2.43, 2.32, and 2.30 eV for S2-11, S2-31, and S2-91, respectively, were obtained from the onset of absorption. The PL spectra of S2 polymers only exhibit single broad emissions, with maxima around 605, 581, and 545 nm for S2-11, S2-31, and S2-91, respectively. The absence of dual emissions observed in solution indicates that the energy transfer from the carbazole fragment to the TADF chromophore is more efficient in neat films than that in dilute solution, similarly to previous conclusions in some publications 217 . In addition, the gradual redshift of the emission band with the increasing Pm5 unit content in the polymers is also due to the gradual change of the polarity of the medium (more and more polar). From the absorption and emission spectra, the Stokes shift can be calculated for S2-11, S2-31, and S2-91 as well and the values are quite similar to the ones determined in solution (Table3.3.4).

Figure 3 . 3 . 8

 338 Figure 3.3.8 The UV-vis absorption and PL spectra of S2 polymers in neat films.

  To estimate the energy levels of the excited states of S2 polymers in neat film, the singlet and triplet energy values (ES and ET) were determined from the fluorescence and phosphorescence spectra, respectively (Figure 3.3.9). The ES values of S2-11, S2-31, and S2-91 are 2.50, 2.63, and 2.81 eV, and the ET values of S2-11, S2-31, and S2-91 are 2.44, 2.56, and 2.71 eV, respectively. The values of S2-11, S2-31, and S2-91 were calculated to be 0.06, 0.07, and 0.10 eV, respectively.

Figure 3 . 3 . 9

 339 Figure 3.3.9 Fluorescence (300K) and phosphorescence (17K) spectra of S2 polymers in neat film measured by a streak camera.

Figure 3 . 3 . 10

 3310 Figure 3.3. 10 Photoelectron spectra of S2 polymers in neat film.

  Time-resolved measurements TADF feature of S2 polymers was further confirmed by analysis of the neat and doped films transient PL characteristics using time-resolved fluorescence spectroscopy with time-correlated single-photon counting (TCSPC) and a streak camera. The transient PL decay spectra of S2 polymers in neat films were preliminarily recorded by the TCSPC technique (Figure 3.3. 11). For S2-11 and S2-31, the PL decay curves are almost overlapped in either argon or air atmosphere, while S2-91 displays a clear difference. Similar to the phenomena in toluene, both PF and DF components can be clearly observed in the transient PL decay curves in argon:the PF component can be fitted with a mono-exponential, while the DF component can be fitted with a bi-exponential function. The data are summarized in Table3.3. 6. And the polymers possess shorter PF and DF lifetimes, with an increasing ratio of the acceptor units in the polymer.

Figure 3 . 3 .

 33 Figure 3.3. 11 Transient PL decay spectra of S2 polymers in neat films recorded by TCSPC.

3 . 12 .

 312 The fluorescence decay spectra of S2 polymers consist of a similar nanosecond-scale component and a varying microsecond-scale component, which are ascribed to the prompt and delayed fluorescence, respectively. As already observed in section 3.2.2.2, the DF components of the different neat films in vacuum are longer than those observed by TCSPC under simple argon flow. This indicates that the Ar flow is not enough to remove all the O2 in the films and that the PLQYs in neat film determined previously are probably a little underestimated. The DF lifetimes of S1 polymers at room temperature in vacuum are summarized in Table3.3.7. The PF components exhibit almost no variation with temperature, but the DFs change significantly with temperature as shown inFigure 3.3.12.

Figure 3 . 3 . 12

 3312 Figure 3.3. 12 The temperature-dependent PL decay spectra of S2 polymers in neat films measured by a streak camera from 50 to 300 K.

  The transient PL decay curves of S2 polymers were further investigated in CBP doped films (10 wt%), as represented in Figure3.3. 13. Similar to the curves in neat films, even though there is no distinct difference between the PL decay curves in argon and air atmosphere, all the PL decay curves are composed of two obvious components: prompt and delayed components.

Figure 3 . 3 . 13

 3313 Figure 3.3. 13 The fluorescence decay curves of S2 polymers in CBP doped films at room temperature.

Figure 3 . 3 .

 33 Figure 3.3. 14 Temperature-dependent PL decay spectra of S2 polymers CBP doped films (10 w%t) measured in vacuum by a streak camera from 50 to 300 K.

Figure 3 . 3 . 15

 3315 Figure 3.3. 15 Energy level diagram for the OLED device based on S2-11.

Figure 3 . 3 .

 33 Figure 3.3. 16 OLED performance of S2-11: a) EL spectra at various voltage; b) EQE vs current density c) Current density-voltage-luminance curves; d) Current efficiency and EQE vs luminance.

Figure 3 . 4 . 1

 341 Figure 3.4.1 Chemical structures of TADF model 26IPNDCz and S3 polymer series.

Figure 3 . 4 .2 1 H

 341 Figure 3.4.2 1 H NMR spectra of monomers 4A and 4E.

Figure 3 . 4 .

 34 Figure 3.4.3 1 H NMR spectra of S3 polymer series in CD2Cl2.

Figure 3 . 4 . 4

 344 Figure 3.4.4 SEC curves of S3 polymers.

polymers (S3- 11 ,

 11 S3-31, and S3-91) in dilute toluene solutions are depicted in Figure 3.4.5. The polymers show absorption at around 294 nm which are mainly ascribed to the π-π transition of carbazole and isophthalonitrile units in diluted toluene. In the meanwhile, these polymers display wellresolved emission spectra whose maximum are located at 424, 425, and 427 nm for S3-11, S3-31, and S3-91, respectively.

Figure 3 . 4 . 5

 345 Figure 3.4. 5 The normalized (a) UV-Vis absorption and PL (RT) and (b) phosphorescence (77K) spectra of S3 polymers in toluene.

From

  photoluminescence properties.

Figure 3 . 4 . 6

 346 Figure 3.4. 6 The transient PL decay curves of S3-11, S3-31, and S3-91 in toluene under air and nitrogen atmosphere.

Figure 3 . 4 . 7

 347 Figure 3.4. 7 The normalized UV-Vis absorption, PL (a), and phosphorescence (b) spectra of S3 polymers in neat films at room temperature.

  As represented inFigure 3.4.8, the HOMO energy level of S3 polymers was determined in neat films by photoelectron spectroscopy and the values are equal to -6.19, -6.20, and -6.22 eV for S3-11, S3-31, and S3-91, respectively. LUMO energy level can be deduced as the sum of the HOMO and the optical energy gap.

Figure 3 . 4 . 8

 348 Figure 3.4. 8 The photoelectron spectra of S3 polymers in neat film.

Figure 3 . 4 .

 34 Figure 3.4. 10 Temperature-dependent transient PL decay curves over the 50 to 300 K temperature range for S3-91 neat film.

Figure 3 . 5 .

 35 Figure 3.5. 2 1 H NMR spectra of 5A and 5B in dichloromethane.

  .5.3, the signals belonging to the vinyl groups of 5A and 5B disappeared completely, demonstrating that no monomers (or oligomers) remain in the polymers. Besides, new signals, ascribed to the protons of the polymer backbones, appear from 2.50 to 1.60 ppm, and the sharp peaks corresponding to signals of protons of the aromatic rings became broad, indicative of the successful polymerization.The broad peaks in the range of 7.90-9.0 ppm are attributed to electron-accepting units (5B) in the polymers. The broad peaks, in the range of5.7-6.3, 6.67-7.09 ppm, correspond to the signals of protons of the electron-donating unit (5A). The peak around 7.3 ppm is probably attributed to both aromatic side groups.

Figure 3 . 5 . 3 1 H

 351 Figure 3.5. 3 1 H NMR spectra of S4 polymers.

Figure 3 . 5 . 4

 354 Figure 3.5. 4 The zoom of 1 H NMR spectra of S4 polymer.

Figure 3 . 5 . 5

 355 Figure 3.5. 5 SEC curves of S4 polymers.

Figure 3 . 5 .

 35 Figure 3.5. 6 a) The normalized UV-Vis absorption and PL spectra of S4-11, S4-31, and S4-91 in toluene; b) The PL spectra of S4-91 in toluene at the air, N2, and O2 atmosphere.

Figure 3 . 5 . 7

 357 Figure 3.5. 7 The transient PL decay curves of S4-11, S4-31, and S4-91 in toluene under air and N2 atmosphere

  5. 4. The absorption spectra of S4 polymers demonstrate the main band at 297, 293, and 290 nm for S4-11, S4-31, and S4-91), corresponding to the π-π transition of the aromatic groups. The optical energy gap of 2.95, 2.97, and 3.05 eV for S4-11, S4-31, and S4-91, respectively, were obtained from the onset of absorption peaks. The PL spectra display similar sole and broad CT emission with maxima at 541, 532, and 505 nm for S4-11, S4-31, and S4-91, respectively. Note that the slight blue-shift of the emission spectra when the quantity of acceptor units decreases along the polymer backbones is consistent with the decrease of the medium polarity.

Figure 3 . 5 . 8

 358 Figure 3.5. 8 The normalized UV-vis absorption, photoluminescence (a), and phosphorescence spectra (b, at 77K) of S4-11, S4-31, and S4-91 in neat film.

  .5. 9, the HOMO energy level of S4 polymers was also determined in neat films by photoelectron spectroscopy and the values are -5.99, -5.95, and -5.95 eV for S4-11, S4-31, and S4-91, respectively. Thus, LUMO energy levels were deduced from the HOMO and the optical energy gap measured by UV-Visible measurements (seeFigure 3.5.4).

Figure 3 . 5 . 9

 359 Figure 3.5. 9 The photoelectron spectra of S4 polymers in neat film.

Figure 3 . 5 .

 35 Figure 3.5. 10 The PL decay curves of S4-11, S4-31, and S4-91 in neat film measured by a streak camera at RT in vacuum.

Figure 3 . 5 . 11

 3511 Figure 3.5. 11 The temperature-dependent time-resolved PL spectra of S4-91 measured by a streak camera (100-300K) in vacuum.

  -phenyl)-5-(5-octyl-thiophene-2-yl)-[1,3,4]oxadiazole (0E). 5-n-octylthiophene-2carbonyl chloride (0C)(2.7 g, 10.5 mmol) and 5-(4-methoxy-phenyl)-2-h-tetrazole (0D)(1.54 g, 8.7 mmol) were dissolved in 10 mL of pyridine under an atmosphere of Ar. The resulting solution was heated under reflux for 12 hours. The reaction was cooled down to room temperature and successively quenched by pouring 50 mL of water, causing the precipitation of a yellow solid (Yield: 2.4 g, 74%). 1 H NMR (300 MHz, CDCl3): δH = 8,04 (2H, m, 3-Harom), 7.62 (1H, d, J = 3.7, 2-Harom), 7.02 (2H, m, 4-Harom), 6.85 (1H, m, 1-Harom), 3.89 (3H, s, -OCH3), 2.87 (2H, t, J = 7.5 Hz, -CH2-Ar), 1.73 (2H, m, Haliph), 1.41-1.28 (10H, m, Haliph), 0.88 (3H, t, J = 6.7 Hz, -CH3). 13 C NMR (75 MHz, CDCl3): δC = 162.

  Phenol)-5-(5-octyl-thiophene-2-yl)-[1,3,4]oxadiazole (0F). 2-(4-methoxy-phenyl)-5-(5-octyl- in dry diethyl ether (100 mL) was added dropwise in the above mixture over 1 h and the resulting Grignard mixture was stirred under reflux overnight.3-Bromothiophene (1.21 g; 7.455 mmol), Ni(dppp)Cl2 (0.038 g; 0.07 mmol), and dry diethyl ether(40 mL) were placed in a second flask and the mixture was cooled down to 0 o C. The resulting Grignard mixture was then slowly transferred via cannula to the second flask under argon. The mixture was heated to reflux for 24 h before quenched by a cold 0.2 M HCl and extracted with CH2Cl2. The organic phase was washed with water until pH = 7 and then dried over MgSO4. White solid was obtained after removing the solvent by vacuum evaporation and further purified by column chromatography (petroleum ether: diethyl ether = 15:1, silica gel) (Yield: 1.8 g, 58%).1 H NMR (400 MHz, CDCl3): δH = 7.24 (1H, dd, J = 4.9 Hz, J = 3.0 Hz),6.96-6.92 (2H, m), 6.84 (4H, s), 3.91 (2H, t, J = 6.6 Hz), 3.77 (3H, s), 2.63 (2H, t, J = 7.8 Hz),1.76 (2H, m),1.63-1.59 (2H, m), 1

8 x 10 4 ,

 4 Mw/Mn = 1.47, DP = 31 (SEC-THF, PS Standard);1 H NMR (600 MHz, CDCl3): δH= 7.96 (2H, s, Harom), 7.55 (1H, s, Harom), 6.96 (3H, m, Harom), 6.80 (1H, s, Harom), 3.94 (2H, s, -CH2-O), 2.82 (4H, m, -CH2-Ar), 1.75-1.69 (8H, m, Haliph), 1.42-1.31 (22H, m, Haliph), 0.86 (3H, s). (1B, 2.2 g, 6.35 mmol) and N-bromosuccinimide(1.246 g, 7 mmol) were dissolved in 10 mL of dry DMF. After stirring at room temperature in dark overnight, the mixture was poured into cold water (100 mL) and extracted with diethyl ether (3 x 100 mL). The organic phase was washed with water (3 x 100 mL), dried over anhydrous MgSO4 and the solvent was removed in vacuum. The crude product was further purified by column chromatography (petroleum ether, silica gel) as a yellow liquid (Yield: 2.2 g, 81%).1 H NMR (400 MHz, CDCl3) δH = 7.19 (d, J = 5.6 Hz, 2H), 6.83(s, 4H), 6.78(d, J = 5.6 Hz, 2H), 3.90(t, J = 6.6 Hz, 2H), 3.77(s, 3H), 2.56(t, J = 7.5 Hz, 2H), 1.75(m, 2H),1.56(m, 2H), 1.44(m, 2H), 1.30(m, 10H

  All glasswares were dried in an oven (60 o C) before manipulation. 2-bromo-3-(10-(4-methoxyphenoxy)decyl)thiophene(1.7 g, 4 mmol), PdCl2(PhCN)2 (46 mg, 0.12 mmol), potassium fluoride (KF) (0.465 g, 8 mmol) were added to 18 mL dry DMSO under argon. After stirring for 5 min, AgNO3(1.36 g, 8 mmol) was added in one portion. After stirring at 60 o C for 3 h, the same amount of PdCl2(PhCN)2, KF and AgNO3 were added and the mixture was stirred at 60 o C for another 18 h. After cooling down to room temperature, the mixture was filtered over a silica gel plug and the residue was washed with 250 mL of CH2Cl2.

  50 mL of dry DMF. After bubbling for 15 min, NaH (260 mg, 12 mmol) was added into the above solution under an argon atmosphere. After stirring for 1 h, 9-(bromomethyl)pentadecane (4.58 g, 15 mmol) was added under argon. After stirring at room temperature for 4 days, 2 mL of water was added to quench the reaction and DMF was removed via distillation. The resulting mixture was further dissolved in DCM and the organic phases were washed

  bis(pinacolato)diboron (2.29 g, 9 mmol) was dissolved in dry 1,4-dioxane (75 mL).

  dry DMF and NaH was added slowly into the solution under argon atmosphere. After stirring for 1 h, 2-chloroisophthalonitrile (2D) (10 mol) was added slowly and the mixture was stirred at room temperature for 24 h. The reaction was quenched by adding 2 mL of water and DMF was removed under vacuum. The obtained mixture was dissolved in DCM and washed by water, brine, and dried over anhydrous MgSO4. After filtration and evaporation, the crude product was further purified by column chromatography to give, among other fractions, a yellow solid (Yield: 450 mg, 15%).1 H NMR (400 MHz, THF) δ 10.

9-( 4 -

 4 Vinylphenyl)-9H-carbazole (4A). 9-(4-Vinylphenyl)-9H-carbazole was synthesized according to the literature 269 . To a solution of triphenylmethylphosphonium idode (3.27 g, 8.1 mmol) in 6mL of THF, t-BuOK (1 g, 8.7 mmol) was added under argon at 0 o C and the solution turns yellow. After stirring for 30min, N-(4-formylphenyl)carbazole (1.465g, 5.4 mmol) was added at 0 o C under argon.

- 1 , 3 -

 13 dicarboxylic acid (4B). Following the reference 268 , 2,6-dimethylbromobenzene (10 g,54 mmol) was dissolved in the mixture of t-BuOH (77mL) and water (150 mL), and the mixture was heated to 110 o C. Then, KMnO4 (51.2 g, 324 mmol, 6 equiv.) was added portionwise into the hot mixture during 1 hour. The reaction mixture was heated at 110 o C for S3-991: 1 H NMR (400 MHz, CD2Cl2) δ =

. 1 H

 1 NMR (400 MHz, CD2Cl2) δ = 7.70 (d, J = 8.26 Hz, 2H), 7.47(dd, J = 1.75Hz, J = 7.56Hz, 2H), 7.31(d, J = 8.30 Hz, 2H), 6.98-6.83 (m, 5H), 6.31(dd, J = 1.55 Hz, J = 7.94Hz, 2H), 5.90 (d, J = 17.59 Hz, 1H), 5.40 (d, J = 10.89 Hz, 1H),

  )pyrimidine-5-carbonitrile (5B). 2-(4-Vinylphenyl)pyrimidine-5-carbonitrile was prepared via Suzuki reaction. 4-Vinylphenylboronic acid (1.8 g, 10 mmol) and 2-chloropyrimidine-5carbonitrile(1.4 g, 10 mmol) were dissolved in 200 mL of 1,4-dioxane. Then, aqueous K3PO4 (2M, 25 mL) was added to the above solution, as well as Pd2(dba)3 (458 mg, 0.5 mmol) and Sphos (205 mg, 0.5 mmol) subsequently. After three freeze-thawing cycles, the mixture was heated at 100 o C for 4 h.

  S3 polymersAs the formula of 4A and 4E are C20H15N and C16H10N2, respectively, so the real compositions of S3

  b x value calculated according to the C:N ratio of EA results; c x value calculated according to the H:N ratio of EA results; d xEA value is the average of x b and x c . These data were calculated on the condition of only considering repeating units.

Figure S3

 S3 Figure S3Absorption and emission spectra of S1 polymers in CBP doped film (10 wt%).

Figure S4

 S4 Figure S4Absorption and emission spectra of S1 polymers in mCP doped film (10 wt%).

Figure S5

 S5 Figure S5Absorption and emission spectra of S2 polymers in blend films (10 wt% in mCP).

Figure S6

 S6 Figure S6Absorption and emission spectra of S2 polymers in blend films (CBP).

  photophysiques : c'est pourquoi plusieurs stratégies sont apparues comme des moyens très efficaces pour atteindre cet objectif.

  Un second objectif a été d'explorer 2 familles de nouveaux polymères D-A pouvant présenter un activité TADF (fluorescence retardée activée thermiquement): une première famille est composée de polymères (S1, S2) présentant un squelette donneur de carbazole ou acridan et des groupements accepteurs (tels que dicyano-benzene ou cyano-pyrimidine) en groupes pendants. La deuxième famille se compose de deux nouvelles séries de polymères vinylique (S3, S4) à base des mêmes groupement donneurs et accepteurs utilisés dans la première famille, interagissant à travers l'espace. Les propriétés photophysiques en solution et en film de ces composés ont été étudiées et leurs activités TADF ont été caractérisées. Aussi, c'est la raison pour laquelle dans cette thèse, le chapitre 1 fournit une introduction générale décrivant les principes de conception et les méthodes de synthèse contrôlée pour le réglage des propriétés électroniques des polymères semi-conducteurs organiques conjugués en général, avant de décrire également certaines méthodes spécifiques de synthèse contrôlée. Par la suite, nous présentons dans le chapitre 2 (respectivement chapitre 3) la conception, la synthèse et la caractérisation de nouveaux polymères testés comme alternatives aux OFET (respectivement OLED). Le chapitre 2 traite de la conception, de la synthèse et de la caractérisation de nouveaux polymères structurés π-conjugués pour les applications OFET. En effet, dans ce contexte, les propriétés de transport des porteurs de charges dépendent non seulement des propriétés électroniques intrinsèques des matériaux, mais également de la manière dont les molécules sont emballées ensemble en vrac. Par conséquent, l'un des paramètres clés pour améliorer les performances de tels composants à base organique est le développement de systèmes π-conjugués structurés et / ou plus ordonnés. Des exemples technologiques représentatifs sont le domaine de la microélectronique organique où la structuration des semi-conducteurs à canal p et n est l'un des principaux obstacles à l'implantation de l'OSC dans un circuit logique complémentaire organique. La première partie de ce chapitre 2 est consacrée à la bibliographie dans ce domaine spécifique (section 2.1): nous détaillons brièvement les mécanismes fondamentaux régissant les OFET, avant de décrire différentes familles de matériaux cristaux liquides. Ensuite, nous présentons une classe de matériaux organiques capables de donner spontanément des auto-assemblages, c'est-à-dire des cristaux liquides organiques, en se concentrant sur les systèmes π-conjugués et notamment les polymères. Les deux sections de résultats suivantes (sections 2.2 et 2.3) traitent de la conception, de la synthèse et de la caractérisation de nouveaux matériaux π-conjugués structurés cristaux liquides pour les futures applications OFET, à la recherche de propriétés ambipolaires potentielles. En effet, seules quelques nanostructures présentant les deux propriétés électroniques différentes, telles que les comportements des donneurs d'électrons et des accepteurs d'électrons, ont été étudiées jusqu'à présent pour les applications OFET. Plus précisément, dans la section 2.2, nous décrivons la synthèse et la caractérisation d'une architecture supramoléculaire résultant de la séparation de phase, à l'échelle nanométrique, de deux systèmes π-conjugués liés de manière covalente. Nous rapportons l'étude d'un polymère dit (Polythiophène-oxa), composé d'un poly (3-alkylthiophène) donneur d'électrons régiorégulier comme squelette et d'entités calamitiques types oxadiazole accepteurs d'électrons comme groupes latéraux. Dans la section 2.3, de même sont explorées les propriétés d'un polymère nommé (PBTTT-Tri) qui consiste cette fois en un squelette de type donneur étendu, à savoir le poly (2,5-bis (3alkylthiophén-2-yl) thiéno [3,2-b] thiophène) (PBTTT), ainsi que des groupes latéraux discotiques de type triphénylène comme contrepartie accepteur. Pour les deux types d'architectures macromoléculaires, nous décrivons d'abord l'optimisation de la stratégie de synthèse mise au point, avant de présenter la structure chimique mise en évidence par RMN et SEC essentiellement. Deuxièmement, le comportement thermique et d'auto-organisation des polymères est étudié plus en détail par POM, DSC et XRD. Troisièmement, les propriétés préliminaires de transport de charge des matériaux, évaluées en configuration OFET, sont discutées. Enfin, nous conclurons cette partie par quelques perspectives basées sur les nouvelles lignes directrices de conception que nous avons pu tirer de cette étude. Concernant nos apports dans le cas du (Polythiophène-oxa), nous avons tout d'abord développé une voie chimique innovante, même si le nombre d'étapes est plus long, pour atteindre un monomère de thiophène à substitution bromo-alkyle plus pur, conduisant à une méthode améliorée de préparation

Table 1 .1. 1

 1 Summary of merits and demerits of different types of films

	Films	discrete molecules vacuum-processed	discrete molecules solution-processed	polymer solution-processed
	fabrication cost	high	low	low
	material purity	high	high	low
	thermal stability	high	low	high
	large-area production	difficult	easy	easy
	multicomponent layer	difficult	easy	easy
	multilayer structure	easy	difficult	difficult
	molecular orientation	high degree	small anisotropy	high degree

Table 2 .2. 1

 2 The structural information of Polythiophene-Br and Polythiophene-oxa

	Polymers	Mn,SEC	Mw/Mn	Xn,SEC	Xn,NMR	Xn,SEC/Xn,NMR
	Polythiophene-Br	1.03 x 10 4	1.22	34	20	1.7
	Polythiophene-oxa	1.8 x 10 4	1.47	31	18	1.7
	2.2.2 Thermal and self-organization behavior study of Polythiphene-oxa
	The thermal behavior of Polythiophene-oxa was examined by POM and DSC (Figure 2.2.4). Because
	of the high viscosity of the obtained thin film, Polythiophene-oxa doesn't develop any characteristic
	optical mesophase texture under POM. However, on heating, a birefringent and homogeneous texture
	can be observed from room temperature to around 140 o C indicating an anisotropic medium. On
	further heating, the viscous bright phase started to transform slowly to a non-birefringent isotropic
	phase.

Table 2 . 3

 23

	Polymers	Mn,SEC	Mw/Mn	Xn,SEC
	PBTTT-Br	1.5 x 10 4	1.6	20
	PBTTT-Tri	2.0 x 10 4	1.5	10

.

1

The structural information of PBTTT-Br and PBTTT-Tri

Table 3 .1.1

 3 Photoluminescence and electroluminescence of linear conjugated TADF polymers

	Polymers	(nm)	ΔEST (eV)	(%)	(ns)/ (μs)	(nm)	Von (V)	Lmax (cd/m 2 )	CE/PE/ EQE	C.I.E	EL
	pCzBP 212	508 b	0.18 b	23/16 b	13/74 b	500	6.0	5100	24.9/9.0/8.1	0.28,0.43	G
	pAcBP 212	540 b	0.10 b	46/27 b	24/10 b	548	4.3	30800	31.8/20.3/9.3	0.38,0.57	Y
	PTCz 213	573	0.19 a	17/16.3	29.9/2.35	590	-	2733	6.5/13.7/8.6	0.51, 0.48	R
	PTD 213	629	0.05 a	8/7.9	22.9/2.53	670	-	514	0.91/0.46/0.24	0.64, 0.36	R
	PCzDPT5 213	591 c	-	50/14	38.4/5.24	432, 602	-	2553	3.2/5.2/4.1	0.55, 0.41	R
	P12 214	494	-	33.7/4.5	8.82/2.36	506	3.1 c	-	10.7/11.2/4.3	0.24,0.43	G
	PAPCC 216	487	0.37	8/0.5	5.8/0.50	508	3.0	554	3.6/3.67/1.34	0.25,0.47	G
	PAPTC 216	507	0.13	28/3.9	13.8/0.68	521	2.6	10251	41.8/37.1/12.63	0.30,0.59	G
	PCzAPT10 218	507	-	90/57.3	11.1/2.52	-	2.57	33262	-/48.5/16.9	0.35,0.54	G
	PCzATD5 219	531	0.09	89/45	27.9/1.1	555	2.57	15456	48.7/50.5/15.5	0.41,0.55	Y
	PCzABA10 220	521	0.22	51/34.8	21/1.272	-	2.7	-	35.3/30.1/10.6	0.39,0.57	-
	PABPC5 221	525	0.12	77/41.9	22/1.286	-	2.6	-	60.5/61.2/18.1	0.40,0.56	-
	PCzAB2Py5 222	555	0.10	62/28.3	32/0.951	573	3.0	-	34.2/26.3/11.9	0.48,0.51	Y
	PCzA3PyB5 222	555	0.16	35/13.3	19/1.134	568	2.6	-	15/14.4/5.2	0.47,0.51	GY
	PCzAB3Py5 222	544	0.10	65/27.3	32/0.876	557	2.9	-	39.2/33.1/12.2	0.44,0.54	G
	Cop-10 224	540	0.0428	21/9.9	82/2650	578	3.2	3000	42.9/45/15.7	0.46,0.49	Y
	PTDP-5 225	427, 537 b	0.06	100 c /-	14.7/283	428, 600	3.7	1247	4.8/11.6/7.1	0.38,0.35	W
	PFSOTT2 226	416, 567	0.26	76 (99 b ) /7.8	25.4/6.2	616	9	3771	8.1/1.8/4.8	0.55,0.43	R
	P3 228	508	0.18	81/72	4.4/124.5	507	3.9	-	26.0/18.5/8.7	0.23,0.40	G
	PCzDP-10 214	500	-	74/53	19.5/2.0	496	-	-	38.6/14.3/16.1	0.22,0.40	BG
	Poly(AcBPCz-TMP) 232	498	0.12	68	27.2/4.44	507	3.2	13500	68.8/60.0/23.

Table 3 .1.2

 3 Photoluminescence and electroluminescence of non-conjugated TADF polymers

	Polymers	(nm)	ΔEST (eV)	(%)	(ns)/ (μs)	(nm)	Von (V)	Lmax (cd/m 2 )	CE/PE/ EQE	C.I.E	EL
	LEP 210		0.22	43.6	-	-		-	-/-/10	0.32,0.58	G
	P(DMTRZ-Cp) 233b		0.023	97/48	12.2/1.8	528	4.0	-	50.5/31.8/15.4	0.35,0.57	G
	Copo1 234		0.35	-	-	533	5.8	-	40.1/61.3/20.1	0.36,0.55	G
	PCzPT-19 235b		0.06 a	21/10.3	35.1/10.2	552	5.2	4388	4.1/1.8/1.2	0.40,0.55	G
	POPT-25 235b		0.11 a	36/21.2	36.7/3.0	540	6.4	3386	16.8/7.8/5.2	0.36,0.50	G
	P2 236		0.06	23.5 d /-	-	-	2.9	1764	11/12.3/4.5	0.45,0.40	Y
	P3 236		0.04	19.5 d /-	-	-	2.9	1753	23/32.8/10.4	0.37,0.38	W
	PDTPT-1 247		0.03 f 0 .02 g	69/21 e ,61 f	-/6.9 e ,15.5 f	-	3.5	2900	38.8/20.3/14.2	0.33,0.42	W
	P12 237		-	64/22	24.1/1.9	552	4.4	14490	20.6/7.3/6.9	0.40,0.54	G
	VTD38 238		0.07	70.9/35	22.0/3.3	517	4.0	1953	76.3/53.2/22	0.30,0.53	G
	PBD-10 239		-	42/20	26.4/5.9	478	3.8		13.5/-/7.3	0.20,0.29	B
	PDT-2 240		0.03	54/40.8	-/5.87	436	5.0	993	8.7/3.9/5.3	0.15,0.09	B
	PFDMPE-R05 242		-	32/-	4.2/126	606	9.8	1677	10.3/3.2/5.62	0.57,0.42	R
	PCzDMPE-R07 241		-	27/	5.4/145	611	5.2	1124	3.35/1.88/2.03	0.58,0.41	R
	PTF-20 244		0.08	53	24/0.98				20.1/-/7.0	0.29,0.47	B
	P1-05 245		0.04	29/15.4	66/0.36	455	3.2	1902	10.6/-/7.1	0.17,0.17	DB
	P2-05 245		0.02	51/43.9	40/1.91	472	3.2	6150	21.8/-/12.1	0.18,0.27	B
	P3-05 245		0.04	74/68.8	44/1.98	525	3.0	10273	50.3/-/16.2	0.34,0.55	G
	P4-05 245		0.05	34/29.6	53/0.82	568	3.2	5339	21.1/-/7.8	0.46,0.50	Y
	P5-05 245		0.05	6/0.36	44/0.94	616	4.6	1283	1.7/-/1.0	0.57,0.41	R
	WP-0.4 245	-	-	-	-	-	3.2	5173	37.9/34.8/14.1	0.31,0.42	W
	P1 248		-	2.9,15.1/ -	-	-	-
	P2 248		-	7.4,33.8/6270
	P3 248		-	19.0/14.1
	P4 248		-	20.9/1.4,9.4
	P5 248		-	24.0/1.7,10.4
	P6 248		-	22.0/2.7
	P7 248		-	5.7,36.7/2.5

Table 3 .2.1

 3 The structural characterization of S1 polymers

	Polymers	Mn,SEC (kDa)	Xn,SEC	Mw/Mn	C:H:N a	C:H:N b
	S1-11	5.7	10	1.22	76.43 : 6.39 : 7.61	84.48 : 5.67 : 9.85
	S1-11-L	4.8	7	1.41	62.22 : 4.82 : 9.51	84.48 : 5.67 : 9.85
	S1-91	4.5	8	1.20	64.41 : 5.64 : 4.35	86.21 : 7.76 : 6.03

Table 3 .2.2

 3 Photophysical parameters of S1 polymers in solvents.

λabs a

Table 3 .2.3

 3 PF and DF lifetimes of S1 polymers in toluene

		APF		ADF	(μs)
	S1-11	3844.64	33.4	47.8644	1.01	27.4 / 72.6
	S1-11-L	4170.43	39.6	57.11	0.75	20.5 / 79.5
	S1-91	3542.61	42.8	59.8249	0.70	21.5 / 78.5

Table 3 .2.4 The

 3 Measured in air atmosphere; b Measured in argon atmosphere; c Measured by photoelectron spectroscopy; d the optical energy gap calculated from absorption spectra; e deduced from the HOMO and Eg values; f calculated from streak camera experiments.

		λabs, neat	λPL,neat	PLQYneatfilm a/b	HOMO c	Eg d	LUMO e	ΔEST f	Stokes shift
		(nm)	(nm)	(%)	(eV)	(eV)	(eV)	(eV)	(cm -1 )
	S1-11	312	529	3.3 / 3.4	-5.66	2.60	-3.06	0.01	13148
	S1-11-L	307	513	1.8 / 1.7	-5.61	2.67	-2.94	0.02	13080
	S1-91	315	530	4.4 / 4.5	-5.67	2.34	-3.33	0.02	12878

photophysical parameters of S1 polymers in the neat film a

Table 3 .2.5

 3 PLQYs of S1 polymers in mCP doped films with different content (Argon atmosphere)

		100%	50%	40%	30%	20%	10%	5%
	S1-11	3.4	8.8	11.9	14.1	17.5	24.6	25.8
	S1-11-L	1.7	11.1	12.5	14.2	17.0	21.0	24.1
	S1-91	4.5	3.4	5.1	5.5	9.2	8.0	16.3

Table 3 .2.6 PF

 3

		APF	(ns)	ADF1	(ns)	ADF2	(ns)
	S1-11	0.1517	8.7	0.00306	30.0	0.00244	128	5.3 / 18.1 / 76.5
	S1-11-L	0.33248	7.3	0.02667	80.7	0.00304	342	38.3 / 18.5 / 43.2
	S1-91	0.09785	13.6	0.00567	83.2	0.00183	451	17.9 / 31.4 / 50.6

and DF lifetimes of S1 polymers in neat films (argon atmosphere)

Table 3 .2.7

 3 The DF lifetimes of S1-11 in neat films measured by a streak camera (100-300K)

	T (K)	ADF1		ADF2	( s)	R 2
		0.00257	0.290	0.00279	2.87	0.95358
		0.00435	0.259	0.00483	2.02	0.96951
		0.00312	0.258	0.0043	1.74	0.98119
		0.00108	0.207	0.00427	1.37	0.98151
		0.03547	0.166	0.00625	1.24	0.98419
		0.00981	0.159	0.00486	1.07	0.98541
		0.01175	0.107	0.00554	0.79	0.98664
		0.02242	0.092	0.00530	0.66	0.99023

Table 3 . 2

 32

	T (K)	ADF1		ADF2	( s)	R 2
		0.00981	0.299	0.00403	2.04	0.98595
		0.01355	0.268	0.00509	1.78	0.98155
		0.01349	0.281	0.00395	1.63	0.98237
		0.00779	0.348	0.00338	1.75	0.97106
		0.00207	0.210	0.00333	1.28	0.9733
		0.00635	0.231	0.00339	1.23	0.98225
		0.00255	0.192	0.0022	0.96	0.98162

.

8

The DF lifetimes of S1-11-L in neat films measured by a streak camera (100-300K)

Table 3 .2.9 The

 3

	T (K)	ADF1		ADF2	( s)	R 2
		0.01052	1.17	0.00947	6.84	0.99484
		0.01122	1.27	0.00978	5.06	0.99645
		0.01952	0.91	0.01179	3.48	0.99689
		0.01442	0.88	0.00906	3.23	0.99608
		0.01046	0.72	0.00746	2.91	0.99603
		0.01344	0.71	0.00605	2.71	0.99628
		0.00556	0.38	0.00299	1.52	0.98709
		0.00462	0.31	0.00326	1.12	0.97942

DF lifetimes of S1-91 in neat films measured by a streak camera (100-300K)

Table 3 .2.11 DF

 3 lifetimes of S1-91 in mCP doped film (10 wt%) measured by a streak camera

	T (K)	A1		A2	( s)	R 2
	50	0.01779	31.4	0.02602	6.84	0.99339
	100	0.01443	25.3	0.02727	5.59	0.99722
	150	0.0165	22.7	0.11138	4.13	0.99704
	250	0.01085	16.4	0.01606	2.78	0.99495
	300	0.00509	11.8	0.02496	2.20	0.99596

Table 3 .3.1

 3 The physical properties of S2 polymers result from elemental analysis; b theoretical values from feeding ratio without considering end groups predominant role, consequently, a significant blue shift occurs. While for S2-11 and S2-31, the interplay of aggregation and solvatochromism leads to little change in the conjugation of the polymers, resulting in a small red shift in emission.

	Polymers Mn,SEC (kDa)	Xn,SEC Mw/Mn Conversion (%)	C:H:N a	C:H:N b
	S2-11	3.9	5.1	1.28	40	80.08 : 6.89 : 8.52	83.79 : 7.16 : 9.05
	S2-31	4.2	5.4	1.56	28	83.25 : 9.18 : 4.69	85.82 : 8.14 : 6.04
	S2-91	3.4	4.3	1.45	29	83.70 : 9.48 : 4.38	86.76 : 8.79 : 4.44

a

11, S2-31, and S2-91, being

  comprised between 13000 and 19000 cm -1 in toluene or CHCl3 (see

table 3 . 3

 33

.2).

Table 3 .3.2

 3 Photophysical parameters of S2 polymers in solventsThe photoluminescence quantum yields (PLQYs) of the polymers were measured in the presence and absence of oxygen, as oxygen would normally quench the emission from the triplet excited state. As summarized in Table3.3.2, all S2 polymers achieve much higher PLQY in toluene than that in CHCl3, and S2-31 achieves the highest PLQY of 16% and 44% in toluene in air and N2 atmosphere, respectively. Such behavior indicates that these polymers could present TADF properties.

		λabs a	λabs b	λPL a	λPL a	PLQYtoluene c/d	PLQYCHCl3 c/d	Stokes shift
		(nm)	(nm)	(nm)	(nm)	(%)	(%)	(cm -1 ) a/b
	S2-11 288,336 288,335	601	604	10 / 27	0.7 / 0.8	18100 / 18200
	S2-31 298,341 298,343 420,597	584	16 / 44	1.3 / 0.6	16300 / 16400
	S2-91	305	308	421,548 380,516	9 / 23	1.5 / 2.8	14500 / 13100
	a Measured in toluene; b Measured in CHCl3; c Measured in air atmosphere; d Measured after nitrogen-bubbling
	for 15 min.

Table 3 .3. 3 PF

 3 and DF lifetimes of S2 polymer in toluene measured by TCSPC The steady-state UV-Vis absorption and PL spectra of S2 polymers in neat films were shown in Figure 3.3.8. The photophysical properties are summarized in Table 3.3.4. The absorption spectra of S2 polymers in neat films are similar to that in dilute solution, with maxima corresponding to the π-π

		APF		ADF	(ns)
	S2-11	12696.5	17.4	93.0805	532	18.3 / 81.7
	S2-31	15009.2	20.8	105.877	896	23.3 / 76.7
	S2-91	14627	19.4	154.543	458	20.0 / 80.0
	3.3.2.2 In solid-state
	Steady-state measurements
	transition maxima at 293, 296, and 306 nm for S2-11, S2-31, and S2-91, respectively. S2-11 also

Table 3 .3.4

 3 The photophysical parameters of S2 polymers in the neat film Measured in air atmosphere; b Measured in argon atmosphere; c Measured by photoelectron spectroscopy; d the optical energy gap calculated from absorption spectra; e deduced from HOMO and Eg difference; f calculated from streak camera experiments

		λabs	λPL	PLQY a/b	HOMO c	Eg d	LUMO e	ΔEST f	Stokes shift
		(nm)	(nm)	(%)	(eV)	(eV)	(eV)	(eV)	(cm -1 )
	S2-11	293,342	605	6 / 6	-5.53	2.43	-3.10	0.06	17601
	S2-31	296	581	12 / 12	-5.52	2.32	-3.20	0.07	16572
	S2-91	306	545	13 / 23	-5.53	2.30	-3.23	0.10	14331

a

Table 3 .3.5

 3 PLQYs of S2 polymers in CBP doped films with different content

		100%	50%	40%	30%	20%	10%	5%
	S2-11	5.8	10.3	12.9	16.8	24.3	26.0	39.9
	S2-31	12.3	15.4	17.8	23.4	26.6	34.4	35.3
	S2-91	22.9	18.5	24.5	21.4	26.6	27.6	29.6

Table 3 .3. 6

 3 The photophysical parameters of S2 polymers in neat films measured by TCSPC

		APF	(ns)	ADF1	(µs)	ADF2	(µs)
	S2-11	3.75745	4.5	0.00379	0.06	0.0014	0.41	1.3 / 3.3 / 95.4
	S2-31	0.14959	9.8	0.00882	0.12	0.00463	0.68	18.0 / 56.0 / 26.0
	S2-91	0.61875	11.1	0.00181	0.26	0.00073	1.06	5.9 / 9.5 / 84.6

Table 3 .3. 7

 3 DF lifetimes of S2-11 in the neat films(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.00993	0.855	0.00419	5.49	0.98781
		0.01423	0.717	0.00516	5.15	0.98927
		0.02187	0.678	0.00771	3.92	0.9915
		0.0222	0.663	0.00732	3.55	0.99342
		0.01503	0.599	0.0069	3.16	0.99325
		0.01267	0.540	0.00779	2.49	0.99042
		0.01375	0.517	0.00766	2.28	0.99190
		0.01151	0.375	0.00758	1.83	0.99614
		0.22728	0.303	0.01199	1.73	0.99426

Table 3 .3. 8

 3 DF lifetimes of S2-31 in the neat films(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.01046	0.939	0.00812	5.60	0.99182
		0.01177	1.037	0.00715	6.16	0.99451
		0.04293	0.924	0.01014	5.18	0.99456
		0.0271	0.799	0.01076	4.19	0.99437
		0.01675	0.882	0.00826	4.01	0.99666
		0.01651	0.781	0.00802	3.81	0.99674
		0.0268	0.676	0.01144	2.87	0.99577
		0.0289	0.555	0.01336	2.24	0.99623
		0.22597	0.389	0.03118	1.64	0.99508

Table 3 .3. 9 DF lifetimes of S2-91 in

 3 the neat films(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.01598	1.34	0.01495	8.76	0.99602
		0.0616	1.17	0.02545	6.73	0.99623
		0.04202	1.17	0.0231	6.65	0.99724
		0.07957	1.08	0.02571	6.05	0.99756
		0.07159	1.08	0.02295	5.89	0.9980
		0.02879	0.94	0.0208	5.04	0.99778
		0.04818	0.90	0.02188	4.51	0.99798
		0.0497	0.78	0.02262	3.77	0.99745
		0.12344	0.68	0.02806	2.99	0.99805

Table 3 .3. 10

 3 The photophysical parameters of S2 polymers in CBP doped films(10 wt%)

		APF	(ns)	ADF1	( s)	ADF2	( s)
	S2-11	1.01824	20.2	0.0114	0.64	0.0014	2.43	23.3 / 10.9 / 65.8
	S2-31	1.5673	16.2	0.01794	0.85	0.00599	4.21	23.2 / 38.3 / 38.5
	S2-91	0.4106	14.4	0.02375	0.89	0.00434	5.32	42.1 / 46.1 / 11.8

Table 3 .3. 11 DF lifetimes of S2-11 in

 3 CBP doped films (10 wt%)(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.04781	2.99	0.00819	23.6	0.98932
	100	0.03827	2.58	0.01221	18.9	0.99428
	150	0.01393	2.80	0.00973	18.5	0.99487
	200	0.02346	2.49	0.0093	14.3	0.99565
	250	0.01426	2.16	0.00918	11.1	0.99772
	300	0.03866	2.04	0.00748	9.5	0.99719

Table 3 .3. 12 DF

 3 lifetimes of S2-31 in CBP doped films (10 wt%)(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.00646	11.3	0.00549	76.3	0.98686
	100	0.00994	13.4	0.00561	89.0	0.98732
	150	0.00904	9.04	0.00755	62.3	0.98968
	200	0.01734	7.41	0.0092	57.7	0.99292
	250	0.12638	5.82	0.01556	42.9	0.99282
	300	0.04433	3.46	0.02736	18.8	0.99726

Table 3 .

 3 3. 13 DF lifetimes of S2-91 in CBP doped films (10 wt%)(50-300K)

	T (K)	ADF1		ADF2	( s)	R 2
	50	0.00607	10.7	0.00866	82.8	0.98783
	100	0.00906	9.52	0.01086	72.1	0.99054
	150	0.01045	7.81	0.01094	63.7	0.99118
	200	0.02272	6.93	0.01371	63.4	0.98686
	250	0.03154	5.72	0.01874	62.2	0.99002
	300	0.07876	3.34	0.03695	32.2	0.99534
	3.3.3 Electroluminescent properties in device configuration

Table 3 .

 3 the theoretical content of 4E unit in the polymers, calculated from the feed ratio; xEA value is the real content of 4E unit in the polymers, calculated from the EA results; Mn, SEC is the relative number-average molecular weight obtained from SEC measurements in THF eluent, calibrated by polystyrene; Mw/Mn is dispersity; C:H:N is the ratio of C, H and N elements in the polymers, obtained from elemental analysis. Here, the xEA value of S3-991 can't be calculated correctly, because the content of 4E (C16H10N) is too low concerning 2-cyanoprop-2-yl unit (C4H6N), which comes from the decomposition of AIBN and initiates the polymerization.

				4.1 Physical properties of S3 polymers
	Polymers	xt	xEA	Mn,SEC (kDa)	Xn,SEC	Mw/Mn Conversion (%)	C:H:N
	S3-11	0.500 0.549	25	101	1.58	34	84.53 : 4.78 : 8.52
	S3-31	0.250 0.312	21	82	1.51	26	85.58 : 5.12 : 6.99
	S3-51	0.167 0.208	27	103	1.60	40	86.68 : 5.23 : 6.35
	S3-91	0.100 0.123	20	76	1.76	38	86.86 : 5.33 : 5.83
	S3-955	0.050 0.049	18	67	1.40	23	87.41 : 5.47 : 5.42
	S3-991	0.010	-	18	67 a	1.42	26	87.92 : 5.53 : 4.91
	xt value is

a calculated according to the feed ratio of 4A and 4E.

Table 3 .4. 2 The photophysical parameters of S3 polymers in toluene

 3

		λabs (nm)	λPL (nm)	λPhos (nm)	PLQYtoluene a/b/c	Stokes shift (cm -1 )
	S3-11	295,331,345	424	476	18 / 59 / 3	10313
	S3-31	294,334,340	425	485,455	11 / 46 / 2	10484
	S3-91	294,331,340	427	473	11 / 65 / -	10594
	a Measured in air atmosphere; b Measured after nitrogen-bubbling for 15 min; c Measured after oxygen-bubbling
	for 15 min

Table 3 . 4

 34

		APF	(ns)	ADF	(ns)
	S3-11	675.246	30.4	269.246	117	60.4 / 39.5
	S3-31	2100.84	42.1	511.699	182	51.3 / 48.7
	S3-91	1942.26	52.1	480.601	229	52.1 / 47.9

. 3 PF and DF lifetimes of S3 polymers in toluene

11, S3-31, and S3-91, respectively

  , which are mainly attributed to the π-π transition of carbazole and isophthalonitrile in the thin film. The optical energy gap of 2.86, 2.87, and 2.89 eV for S3

-11, S3-31, and S3-91, respectively

  , were obtained from the onset of absorption spectra (Table3.4.4).To estimate the TADF activity of S3 polymers, their singlet and triplet energies were determined according to the fluorescence and phosphorescence spectra, respectively. The ES values of S3

	The PL spectra display broad emission bands at 435, 431, and 426 nm for S3-11, S3-31, and S3-91,
	respectively, corresponding to the CT character of the excites state. As the content of the acceptor
	increases from 10 to 50%, the emission wavelength is slightly red-shifted by 4-9 nm, consistent with
	the increase of the media polarity surrendering the TSCT polymers. 270 Moreover, the Stokes shift can
	be determined by the main characteristics of absorption and emission spectra: 150 nm (12099 cm -1 ),
	140 nm (11162 cm

-1

), 130 nm (10310 cm -1 ), corresponding to S3-11, S3-31, and S3-91 in neat film, respectively

(Table 3.3.4)

. The PLQYs of S3-11, S3-31, and S3-91 in neat films under argon are consequently in the range of 13-15%, much lower than those in dilute toluene solution.

-11, S3- 31, and S3-91 are

  2.71, 2.73, and 2.75 eV and the ET values of S3

-11, S3-31, and S3-91 are

  2.43, 2.46, and 2.48 eV, respectively. The ΔEST values of S3

-11, S3-31, and S3-91 were

  calculated to be 0.28, 0.27, and 0.27 eV, which is quite large compared to those reported TADF polymers, indicating that these polymers might exhibit no or very weak TADF activity in solid-state (Table3.3.4).

Table 3 .4. 4

 3 The photophysical parameters of S3 polymers in the neat film

		λabs	λPL	λPhos	PLQY a	HOMO b	Eg c	LUMO d	ΔEST e	Stokes shift
		(nm)	(nm)	(nm)	(%)	(eV)	(eV)	(eV)	(eV)	(cm -1 )
	S3-11	285,330,343	435	491	13	-6.19	2.86	-3.33	0.28	12099
	S3-31	291,330,343	431	495	15	-6.20	2.87	-3.33	0.27	11162
	S3-91	296,331,343	426	485	13	-6.22	2.89	-3.33	0.27	10310

a Measured in the neat film under argon atmosphere; b Measured by photoelectron spectroscopy; c the optical energy gap calculated from absorption spectra; d deduced from the HOMO and Eg values; e calculated from the fluorescence (RT) and phosphorescence (77K) spectra.

Table 3 .4. 5

 3 PF and DF lifetimes of S3 polymers in the neat filmsThe prompt and delayed lifetimes were calculated from the PL decay curves (50 ns and 50 μs scale, respectively) in vacuum measured by a streak camera.

		APF	(ns)	ADF1	( s)	ADF2	( s)
	S3-11	0.77202	11.1	0.10542	0.20	0.02197	1.01	40.7 / 42.8 / 16.5
	S3-31	0.77454	8.5	0.0098	0.37	0.00475	1.81	19.3 / 45.7 / 35.0
	S3-91	0.88303	9.8	0.02963	0.22	0.01300	1.35	19.9 / 53.6 / 26.5

Table 3 .4. 6 DF lifetimes of S3-91 in

 3

	T (K)	ADF1		ADF2	( s)	( s)	R 2
	50	0.00553	0.56228	0.00664	3.1166	2.78	0.99098
	100	0.02142	0.63832	0.00602	3.54987	2.41	0.99357
	150	0.0216	0.66920	0.00452	3.87327	2.42	0.99144
	200	0.02733	0.63928	0.00378	4.25053	2.37	0.98755
	250	0.0152	0.49809	0.00392	3.26435	2.24	0.97945
	300	0.01523	0.60157	0.00206	4.31297	2.42	0.9797

neat films measured by a streak camera

(50-300K)

Table 3 .5. 1

 3 The structural information of S4 polymers value is the theoretical content of 5B unit in the polymers, determined by the feed ratio; xEA value is the real content 5B unit in the polymers, calculated from the elemental analysis results; Mn, SEC is the relative numberaverage molecular weight obtained from SEC measurements in THF eluent, calibrated by polystyrene; Mw/Mn is dispersity; C:H:N is the ratio of C, H and N elements in the polymers, obtained from elemental analysis.

	Polymers	xt	xEA	Mn,SEC (kDa) Xn,SEC Mw/Mn Conversion (%)	C :H :N
	S4-11	0.500 0.410	39	145	1.85	33	84.53 : 4.78 : 8.52
	S4-31	0.250 0.278	39	174	1.98	45	85.58 : 5.12 : 6.99
	S4-51	0.167 0.220	33	136	1.52	38	86.68 : 5.23 : 6.35
	S4-91	0.100 0.172	28	109	1.44	38	86.86 : 5.33 : 5.83
	S4-955	0.050 0.129	19	70	1.90	39	87.41 : 5.47 : 5.42
	S4-991	0.010 0.080	38	133	1.94	36	87.92 : 5.53 : 4.91

xt

Table 3 .5. 2 The photophysical parameters of S3 polymers in toluene

 3

		λabs (nm)	λPL (nm)	λPhos (nm)	PLQY a/b/c (%)	Stokes shift (cm -1 )
	S3-11	299	564	530	13 / 57 / 1.6	15714
	S3-31	292	566	499	11 / 57 / 3.0	16579
	S3-91	290	374,565	490	11 / 63 / 2.5	16784
	a Measured in air atmosphere; b Measured after nitrogen-bubbling for 15 min; c Measured after oxygen-bubbling
	for 15 min

Table 3 .5. 3 PF

 3

		APF	(ns)	ADF	(µs)
	S4-11	2756.98	203	213.433	0.58	18.2 / 81.8
	S4-31	2757.15	217	46.1219	1.40	9.8 / 90.2
	S4-91	2748.85	214	66.5285	2.17	19.7 / 80.3

and DF lifetimes of S4 polymers in toluene

Table 3 .5. 4

 3 The photophysical parameters of S4 polymers in the neat film

		λabs	λPL	λPhos	PLQY a	HOMO b	Eg c	LUMO d	ΔEST e	Stokes shift
		(nm)	(nm)	(nm)	(%)	(eV)	(eV)	(eV)	(eV)	(cm -1 )
	S4-11	297	540	541	23	-5.99	2.95	-3.04	0.05	15152
	S4-31	293	540	532	33	-5.95	2.97	-2.98	0.04	15611
	S4-91	290	522	505	52	-5.95	3.05	-2.90	0.03	15326

a Measured in argon atmosphere; b Measured by photoelectron spectroscopy; c the optical energy gap calculated from the onset of absorption spectra of polymers in the neat film; d deduced from the HOMO and Eg values; e calculated from the onsets of fluorescence (RT) and phosphorescence spectra (77K).

Table 3 . 5

 35

		APF	(ns)	ADF1	( s)	ADF2	( s)
	S4-11	0.61802	11.7	0.01404	0.63	0.00874	3.6	18.6 / 66.2 / 15.2
	S4-31	0.75455	6.7	0.03148	0.78	0.01522	5.8	20.8 / 74.9 / 4.3
	S4-91	0.52133	6.4	0.04456	0.91	0.05574	7.2	9.1 / 90.1 / 0.8

. 5 PF and DF lifetimes of S4 polymers in neat films

The prompt and delayed lifetimes were calculated from the PL decay curves (50 ns and 50 s scale, respectively) in vacuum measured by a streak camera.

Table 3 . 5

 35

	T (K)	ADF1		ADF2	( s)	( s)	R 2
	100	0.01251	0.840	0.01711	11.6	11.0	0.99199
	150	0.01805	0.793	0.02361	10.9	10.3	0.99391
	200	1.318E-4	0.753	0.02171	9.70	9.7	0.9948
	250	0.06689	0.694	0.04602	8.28	7.5	0.99542
	300	0.01702	0.894	0.04619	7.40	7.1	0.99704
	The average lifetime is calculated using

. 6 DF lifetimes of S4-91 in the neat film measured by a streak camera

  Thionyl chloride(3.9 mL, 54 mmol) was added dropwise via a syringe at 60 o C and then the solution was heated to reflux for 5 h.The reaction mixture was cooled to room temperature. Toluene and excess thionyl chloride were removed in vacuum to give a yellow oil (2.7 g, >95%).1 H NMR (300 MHz, CDCl3):δH= 7.82 (1H, d, J = 4.0 Hz, 6.89 (1H, d, J = 4.0 Hz, 2.86 (2H, t, J = 7.6 Hz, -CH 2 -Ar),1.71 (2H, m, Haliph), 1.33-1.27 (10H, m, Haliph), 0.88 (3H, t, J = 6.8 Hz, -

).

5-n-octylthiophene-2-carboxylic acid (2.6 g, 10.8 mmol)

was dissolved in 15 mL of toluene under an atmosphere of Ar.

  ). 5-(4-methoxy-phenyl)-2-h-tetrazole was synthesized according to the thesis of Andrea Castiglione (Pierre and Marie Curie University).4- methoxybenzonitrile (6.66 g, 50 mmol), sodium azide (4.88 g,75 mmol), and ammonium chloride (4.01 g,75 mmol) were dissolved in 80 mL of DMF under an atmosphere of Ar. The resulting solution was heated at 100°C for 24 hours. The reaction was allowed to cool down to room temperature and HCl was added until precipitation of a white powder occurred and was filtered as well as dried (Yield:

6.4 g, 73%

).

1

H NMR (300 MHz, DMSO-d6): δH = 16.60 (1H, s, NH), 7.98 (2H, d, J = 9.0 Hz, 1-Harom), 7.6 (2H, d, J = 9.0 Hz, 1-Harom), 3.84 (3H, s, -CH3).

[START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF]

C NMR (75 MHz, DMSO-d6): δC = 161.47,

  1 H NMR (600 MHz, CDCl3, T = 50 o C): δH = 7.26 (s, 2H), 7.04 (s, 2H), 3.40 (br t, 4H), 2.79 (br t, 4H), 1.86

  1 H NMR (600 MHz, CDCl3) δH = 7.80 (s, 12H), 7.21 (s, 2H), 7.00 (s, 2H), 4.21(s, 24H), 2.74 (s, 24H), 1.93(s, 24H),1.55 -1.26 (m, 72H), 1.34-0.96 (m, 30H).[START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (151 MHz, CDCl3) δC = 149.41, 124.01, 108.06,

Table S1

 S1 The physical properties of S3 polymers calculated from EA results

	polymers	xt	x a (C:H)	x b (C:N)	x c (H:N)	xEA d
	S3-11	0.500	0.625	0.541	0.556	0.549
	S3-31	0.250	0.301	0.313	0.311	0.312
	S3-51	0.167	0.247	0.205	0.210	0.208
	S3-91	0.100	0.133	0.122	0.124	0.123
	S3-955	0.050	-	0.052	0.046	0.049
	S3-991	0.010	-	-	-	-

Table S2

 S2 The physical properties of S3 polymers calculated from EA results

	polymers	xt	x a (C:H)	x b (C:N)	x c (H:N)	xEA d
	S4-11	0.500	1.034	0.345	0.474	0.410
	S4-31	0.250	0.931	0.226	0.331	0.278
	S4-51	0.167	0.913	0.169	0.270	0.220
	S4-91	0.100	0.876	0.126	0.218	0.172
	S4-955	0.050	0.830	0.088	0.171	0.129
	S4-991	0.010	0.818	0.041	0.120	0.080

H NMR spectra of S3 polymers are represented in Figure 3.4.3. After polymerization, the signals

H NMR (400 MHz, Acetone) δ = 8.60 (s,

2H),7.87 (dd, 2H, J = 8.22, 1.04 Hz), 7.55 (d, 2H, J = 8.20

Acknowledgements

Acknowledgements ................................................................................................................................. Summary .................................................................................................................................................

This work was performed in the équipe Chimie des Polymère (ECP), at the Institut Parisien de Chimie Moléculaire (IPCM) directed by Dr. BOUTEILLER I also want to give my thanks to all the friendly members of ECP. I am grateful for the financial support from CNRS (France) and China Scholarship Council (CSC). And I'd like to thank Prof. ADACHI Chihaya for allowing us to visit and work in the lab OPERA of Kyushu University

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< Copo3 (539 nm) < Homopo (556 nm), indicating the styrene units prevented the aggregation and improved the color purity. Among them, the best EL performance was achieved for Copo1-based device with 20.1% EQEmax, but only remained 5.3% at 100 cd/m 2 . 234 PCzPT-x and POPT-x were prepared to further explorer the effect of a hole-and electron-transporting spacers on TADF features. 235 PCzPT-x and POPT-x had small ΔEST of 0.05-0.07 eV and 0.09-0.13 eV. The PLQYs of PCzPT-x were smaller than 25% while POPT-25 can reach 51% in toluene in nitrogen. Consistent with the photoluminescent properties, POPT-x displayed better TADF performance than PCzPT-x.

POPT-25 also achieved the best EL performance in a solution-processed device with an EQEmax of 5.2%, a CE of 16.8 cd/A, and a PE of 7.8 lm/W with the CIE coordinates of (0.36, 0.50). P1-P3 had small ΔEST (0.04-0.09 eV) and exhibited obvious TADF and aggregation-enhanced emission (AEE) characteristics. 236 P3-based OLED showed warm-white emission with an EQEmax of 10.4%, which is the first reported white-emissive non-conjugated TADF polymers.

Scheme 3.2.1

The synthetic route towards target monomer (for homopolymerization).

To achieve the target homopolymer, a benzene ring bearing a substituent ethylhexyl R1 (-C8H15) was used and 7 steps were proposed to get the desired monomer, as shown in Scheme 3.2.1. However, the 6 th step was not successful and we then modified the synthetic route to start from a benzene ring bearing only a methyl group R2 (-CH3). When using -CH3, the 6 th step was successful but with low yield (<20%). However, after the bromination (7 th step), due to the low solubility of the starting material and the target monomer in common solvents, it was difficult to get pure the target monomer.

Most importantly, the low solubility of this monomer would also lead to poor solubility of the homopolymer, which means that the target homopolymer (R=-CH3) is not a good choice as TADF polymer, considering the fabrication of thin film. Therefore, we decided to modify our polymer design, and an additional comonomer with a long alkyl chain was introduced to improve the final solubility of the polymers (see the final design in Figure 3.2. 3). Besides, this new strategy can limit the possible aggregation-caused quenching and improve the TADF properties. In this strategy, we first prepared the monomer 2E, expected to be TADF chromophore in the polymer, in three steps: the two building blocks, 3,6-dibromocarbazole (2A) and 2-chloroisophthalonitrile (2D)

Final design

were successfully synthesized in one step, respectively. On the one hand, 2A was obtained through the bromination reaction of the commercial carbazole with NBS as the source of the bromine radical (Br•) atmosphere, as shown in Figure 3.2.17. The temperature dependence of the transient PL decay spectra of S1-91 in mCP doped film (10 wt%) was also investigated by a streak camera from 50 to 300 K in vacuum (Figure 3.2.18). We can clearly observe two components in all PL decay curves, among them, the PF components are overlapped with each other. While the delayed components show clear temperature dependence and each component can be fitted with a bi-exponential function (

Photophysical properties

The steady-state and the time-resolved fluorescence of S2 polymers were investigated in solution and solid-state. These investigations were performed in collaboration with the OPERA laboratory at Kyushu University in the scope of the JSPS core-to-core program between OPERA and IPCM (one month stay at OPERA in 2019).

In dilute solution

Steady-state measurements

The steady-state UV-vis absorption and photoluminescence (PL) spectra of S2 polymers in dilute toluene and chloroform are depicted in Figure 3.3.5 and Figure 3.3.6, respectively, and their photophysical properties in two different solvents are summarized in Table 3.

Through-space charge transfer (TSCT) TADF polymers based on Pm5

In this section, using the same strategy as in section 3.4, we designed another series of TSCT polymers (S4) but incorporating this time in the side chain and separately the donor and acceptor entities used in the TADF chromophore Pm5 266 (see Figure 3.5.1). After the description of the synthetic aspects, we will characterize their photophysical properties and determine if these new materials exhibit TADF activity with high PLQY. For the synthesis of this polymer series S4, two monomers were prepared in one step from the commercially available starting materials, respectively. As shown in Scheme 3.5.1, on the one hand, the electron-donating monomer 5A was obtained from the reaction between the -NH group of 9,9-triplets. This is in agreement with the change of emission intensity of fluorescence spectra in different atmosphere observed in Figure 3.5.6b.

Time-resolved measurements

Theoretically, S4 polymers were designed to exhibit TADF activity via through-space conjugation, thus these polymers might only display TADF behavior in solid-state rather than in dilute solution.

However, S4 polymers are not readily soluble in toluene. As a consequence, the polymers might aggregate in toluene to some extent, thus leading to through-space conjugation in this specific solvent.

We conducted the measurements of transient fluorescence decay under air and N2 atmosphere for the series of S4 polymers in toluene. As shown in Figure 3.5.7, when exposing the solutions to air, the delayed component disappeared, revealing that the delayed emission is originated from the triplet states.

Note that the potential of these materials in solution-processed OLEDs should be investigated very soon and we expect relatively good device efficiencies with low roll-off properties, considering the good PLQYs and the short delayed fluorescence lifetimes of these materials.

General conclusions and perspectives

Conclusions and perspectives

Organic semiconductors (OSCs), i.e. π-conjugated small molecules or polymers, have attracted researchers' attention due to their fascinating electronic and photophysical properties. These OSCs have been widely applied in organic electronics, such as organic electroluminescent diodes (OLEDs), organic photovoltaic cells (OPVs), and organic field-effect transistors (OFETs), since they are lightweight, solution-processable, flexible, and they possess tunable properties. This Ph.D. thesis aims to design and synthesize new π-conjugated polymers for OFET and/or OLED applications.

The first objective of this Ph.D. thesis (chapter 2) was the design, synthesis, and characterization of new side-chain liquid-crystalline π-conjugated polymers consisting of π-conjugated backbones bearing side-on semiconducting mesogenic groups, which can self-organize into an ordered nanostructure.

Two target polymers, i.e. Polythiophene-oxa and PBTTT-Tri, were successfully synthesized through optimized procedures and their chemical structures were determined by NMR, SEC, and elemental analysis. More precisely, Polythiophene-oxa is composed of regioregular poly(3-alkylthiophene) as the backbone and calamitic-type electron-acceptor oxadiazole entities as side groups. Similarly,

backbone and discotic-type triphenylene side groups.

The thermal behavior and self-organization of the polymers were further investigated by POM, DSC, XRD, SAXS, and GIWAX. The preliminary charge transport properties were also evaluated in OFET configuration. More specifically, Polythiophene-oxa was able to self-organize with an alternation of bilayer of calamitic mesogens side groups and of polythiophene backbone monolayers, and it exhibits p-type conduction with a hole mobility of around 1.2 x 10 -3 cm 2 V -1 s -1 in the saturated regime.

PBTTT-Tri can self-organize in a supramolecular arrangement with the alternation of triple rows of triphenylene columns and the backbone monolayer parallel to the substrate plane. PBTTT-Tri exhibits p-type conduction and its hole mobility in the saturated regime is around 1.2 x 10 -5 cm 2 •V -1 •s -1 .

These results are promising and further investigation to promote charge transport properties of the polymers will be performed.

The second objective of this thesis (chapter 3) was to design and explore 2 new families of donoracceptor (D-A) polymers as potential TADF materials. These polymers were successfully synthesized by multi-step chemical strategy and their chemical structures were also determined by NMR, SEC, and elemental analysis. As part of this project, I had the great opportunity to work for around one month in the laboratory of Prof. Chihaya Adachi (OPERA Laboratory) at Kyushu University in Fukuoka (Japan). In OPERA, I carried out the photophysical experiments by myself.

More particularly, two groups of polymers, S1 and S2, were linear conjugated polymers with the architecture of donor units fixed in the backbone and acceptor units endowed in the side chains. These polymers all exhibit typical TADF nature. Besides, one solution-processed OLED device, using S2-11

CBP blend film as the EML, was prepared and achieved a maximum luminance (Lmax) of around 5600 cd/m 2 , with an EQE of 1.9%. The electroluminescent properties could be further optimized by changing the parameters of the device fabrication, as well as doped emitting films and other layers.

S3

and S4 polymers were designed to achieve TADF character by through-space conjugation (TSC).

Unfortunately, only S4 polymers show TADF nature, while the fluorescence decay curves of S3

polymers don't show temperature dependence. Anyway, the preliminary results of S4 polymers are very promising and their photophysical properties in blend films and electroluminescent properties will be investigated soon.

To conclude the work undertaken during my Ph.D., I'd like to point out that this work was focused on the design and organic synthesis. Several synthetic procedures were optimized, in the meanwhile, some synthetic routes were given up. Through numerous attempts, I learned a lot about organic chemistry, experiment skills, and scientific research. ( 5.32, 53.84), acetone (2.05, 29.84 / 206.26), and DMSO (2.50, 39.52). The abbreviations for describing the multiplicity of NMR peaks are: s = singlet, d = doublet, t = triplet, q = quartet, and m = multiplet. The size exclusion chromatography (SEC) was performed using an Agilent 1100 Series SEC equipped with a 300 mm x 7.5 PLgel Mixed-D 5 µm 10-4 Å, a refractive-index (RI) detector, and diode-array UV-vis detector (DAD) (calibration: polystyrene standards). The column temperature and the flow rate were fixed to 40°C and 1mL/min in THF (HPLC-Grade). The THF solution used was filtered using a cellulose filter (pore size: 0.20 μm) before sample injection.

Appendices

The optical textures of the mesophases were studied with a Leitz polarizing microscope equipped with a Mettler FP82 hot-stage and an FP80 central processor. The transition temperatures and enthalpies were measured by differential scanning calorimetry with a TA Instruments DSCQ1000 instrument operated at a scanning rate of 20°C min -1 on heating and cooling. The SAXS patterns were obtained with a transmission Guinier-like geometry. A linear focalized monochromatic Cu Kα1 beam (λ = 1.5405 Å) was obtained using a sealed-tube generator (600 W) equipped with a bent quartz monochromator. In all cases, the crude powder was filled in Lindemann capillaries of 1 mm diameter and 10 μm wall-thickness. The diffraction patterns were recorded with a curved Inel CPS120 counter gas-filled detector linked to a data acquisition computer (periodicities up to 90 Å) and on image plates scanned by Amersham Typhoon IP with 25 µm resolution (periodicities up to 120 Å). GIWAXS measurements were conducted at PLS-II 9A U-SAXS beamline of Pohang Accelerator Laboratory (PAL) in Korea. Samples consisted in layers on a silicon wafer of thirty to sixty nanometers thickness.

The X-rays coming from the vacuum undulator (IVU) were monochromated using Si(111) double crystals and focused on the detector using K-B type mirrors. Patterns were recorded with a Rayonix 2D SX 165 CCD detector. The sample-to-detector distance was about 225 mm for an energy of 11.015

keV (1.1256 Å).

Photoluminescence and electroluminescence characteristics. UV/Vis spectra were recorded on a Shimadzu UV-2501 recording spectrophotometer and the fluorescence spectra were recorded on a Hitachi F-4600 fluorescence spectrophotometer. The PLQY measurements were performed on a Quantaurus-QY measurement system (C11347-11, Hamamatsu Photonics). The steady-state fluorescence decay and lifetime were measured by a single photon counting spectrometer from Edinburgh Instruments (FLS920) with a Picosecond Pulsed UV-LASTER (LASTER377) as the excitation source. Prompt fluorescence (PF), delayed fluorescence (DF), and phosphorescence spectra in solid states were measured under vacuum using a streak camera system (C4334, Hamamatsu Co.).

A nitrogen gas laser (MNL200, LASERTECHNIK BERLIN) with an excitation wavelength of 337nm was used. Excitation light was absolutely cut off by putting a 370 nm long band-pass filter (SCF-50S-37L, SIGMA KOKI CO., LTD.) in front of the photo-detector. The current density-voltage-luminance (J-V-L) characteristics of the OLED were measured using a semiconductor parameter analyzer (Agilent Co., HP4155C) with an optical power meter (Newport, Model 1835-C).

organic phase was washed with water (3 x 15 mL), dried over anhydrous MgSO4 and concentrated under reduced pressure. The crude product was deposited upon a column chromatography with silica gel, using petroleum ether as eluant, to give a colorless oil (Yield: 0.94 g, 76 %); 1 H NMR (400 MHz, CDCl3): δH = 6.77 (1 Harom, s), 3.41 (2H, t, J = 6.8 Hz, -CH2-Br), 2.50 (2H, t, J = 7.6 Hz, -CH2-Ar), 1.85 (2Haliph, m), 1.55-1.29 (14Haliph, m); [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (100 MHz, CDCl3): δC = 143. 08, 131.08, 110.45, 108.08, 34.17, 32.97, 29.68, 29.59, 29.52, 29.43, 29.18, 28.88, 28.30. The organic layer was successively washed by water (3 x 30 ml), dried over MgSO4, and concentrated under reduced pressure. The crude product was then precipitated using methanol and the resulting purple solid was filtered through a Soxhlet thimble. The title compound was obtained (Yield: 320 mg, 44%) after successive extraction with methanol; Mn = 1.03 x 10 4 , Mw/Mn = 1.2, DP = 34 (SEC-THF, PS Standard); 1 H NMR (600 MHz, CDCl3): δH = 6.98 (1H, s, Harom), 3.39 (2H, t, J = 6.8 Hz, -CH2-Br), 2.80 (2H, m, -CH2-Ar), 1.90-1.60 (4H, m, Haliph), 1.50-1.31 (12H, m, Haliph); [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (50 MHz, CDCl3): δC = 139. 98, 133.80, 130.59, 128.73, 34.16, 34.14, 32.95, 30.64, 29.64, 29.59, 29.56, 28.91, 28.31. Under an argon atmosphere, Pd(PPh3)4 (5%) was added into the above mixture and the oxygen was removed by freeze-pump-thaw cycling (3 times). After sealing it, the mixture was heated at 85 o C for 3 days. After cooling down, the mixture was precipitated in cold acetone for three times, and a yellow solid was collected after filtration (Yield: 15-30%).

Poly

10-(4-Chlorophenyl)-9,9-dimethyl-9,10-dihydroacridine (3A). A mixture of 9,9-dimentyl-9,10dihydroacridine (2.09 g, 10 mmol), 1-bromo-4-chlorobenzene (2.3 g, 12 mmol), and t-BuONa (1.92 g, 20 mmol) was dissolved in 100 mL of toluene. After freeze-pump-thaw cycling for three times, Pd2(dba)3 (183 mg, 0.2 mmol) and P(t-Bu)3/HBF4 (0.8 mmol) were added to the initial mixture, always under argon flow. The resultant mixture was refluxed at 110 o C for 18 h. After cooling down to RT, the precipitate was removed by filtration, and the mixture was washed by brine, then dried over anhydrous MgSO4. After filtration and evaporation, the crude product was further purified by column chromatography (eluent: DCM:PE=1:10) and (3A) was isolated as a white powder (Yield: 2.1g, 65%).

1 H NMR (400 MHz, DMSO-d6) δ = 7.73 (d, 2H, J = 6.82 Hz), 7.50 (m, 2H), 6.98 (m, 4H), 6.14 (d, 2H, J = 6.84 Hz), 1.61 (s, 6H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, DMSO) δ = 140. 49, 139.93, 133.44, 131.68, 130.11, 126.91, 125.85, 121.12, 113.95, 35.95, 31.63. overnight. After cooling down to room temperature, 5 mL of ethanol was added to quench the reaction.

The hot mixture was filtered through a 5 cm plug of Celite and the plug was washed with ethanol (10 mL). After removing the solvents from the filtrate under pressure, the remaining solution was acidified with 20% HCl (80 mL). The white precipitate observed was filtered, washed with water (20 mL), and collected (Yield: 6.7 g, 50%). 1 H NMR (400 MHz, DMSO) δ = 13.57 (br, s, 2H, COOH), 7.71 (d, J = 7.6Hz, 2H, Ar), 7.52 (t, J = 7.6 Hz, 1H, Ar). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (75 MHz, DMSO) δ = 168. 21, 137.17, 131.20, 128.26, 116.67.

2-Bromobenzene-1,3-dicarboxamide (4C

). 2-Bromobenzene-1,3-dicarboxamide was synthesized according to the literature 267 . Well dried 2-bromobenzene-1,3-dicarboxylic acid (6.6 g, 2.7 mmol) was suspended in SOCl2 (30 mL) and the mixture was heated to 85 o C for 4 h. After cooling down to room temperature, the excess of SOCl2 was removed under pressure to get 2-bromoisophthaloyl dichloride.

The latter was then dissolved in dry DCM (30 mL). The resulting solution was added to 80 mL of an aqueous solution of NH3 dropwise at 0 o C and a white precipitate appeared during the adding. The mixture was stirred at 0 o C for 30 min to make sure all products have precipitated. After filtration, the collected white solid was washed with water and n-hexane before being dried at 50 o C under pressure (Yield: 3.4 g, 52%). 1 H NMR (400 MHz, DMSO) δ = 7.88 (s, 2H, NH2), 7.57(s, 2H, NH2), 7. 45-7.41(m, 1H), 7.38-7.36 (m, 2H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, DMSO) δ = 169. 32, 140.51, 128.42, 127.53, 115.36.

2-Bromobenzene-1,3-dicarbonitrile (4D).

According to the literature 267 , 2-bromobenzne-1,3dicarboxamide (3.3 g, 13.6 mmol), and NaCl (1.85 g, 30 mmol) were suspended in POCl3 (17 mL, 17.7 mmol) and the mixture was refluxed for 4 h. After cooling down to room temperature, the access POCl3 was removed in vacuum. Then the residue was poured into ice water and stir for 10 min. The brown precipitate was formed, filtered, and washed with water. After drying, the crude product was further recrystallized in hexane to give light brown solids (Yield: 2.7g, 96%). 1 H NMR (400 MHz, CDCl3) δ = 7.89 (d, J = 8.06 Hz, 2H), 7.59 (t, J = 8.0 Hz, 1H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CDCl3) δ = 137. 74, 128.92, 128.55, 118.33, 115.77. were added as well. After three freeze-thawing cycles, the mixture was heated at 100 o C for 0.5 h. The hot reaction mixture was filtered through a 5 cm plug of Celite, before the mixture was washed with water, brine, and finally dried over anhydrous MgSO4. After removing the solvent, the crude product was further purified by silica gel column chromatography (eluent: PE:DCM = 1:1) to give a white powder (Yield: 0.8 g, 70%). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CDCl3) δ = 148. 69, 139.61, 137.25, 136.02, 133.43, 129.59, 128.46, 126.87, 116.76, 116.06, 114.44 ). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CD2Cl2) δ = 148. 74, 139.81, 137.54, 136.28, 134.22, 129.94, 128.93, 126.97, 117.05, 116.14, 114.67.

The general process of polymerization of S3. Monomers (4A and 4E) and AIBN (5%) were dissolved in dry toluene. After three freeze-thawing cycles, the mixture was placed in a temperaturecontrolled oil bath at 60 o C. The mixture was stirred for 48 h before exposure to the atmosphere. The resulting polymer was precipitated in acetone for three times, collected by centrifugation, and dried under a high vacuum to obtain a white solid (Conversion: 23-40%).

S3-11: 1 H NMR (400 MHz, CD2Cl2) δ = 7. 97, 7.67, 7.24, 7.05, 2.41, 2.14, 1.74, 1.52. S3-31: 1 H NMR (400 MHz, CH2Cl2) δ = 7. 97, 7.59, 7.22, 7.04, 2.21, 1.78, 1.53. S3-51: 1 H NMR (400 MHz, CD2Cl2) δ = 7. 96, 7.20, 7.00, 2.20, 1.78, 1.52. S3-91: 1 H NMR (400 MHz, CD2Cl2) δ = 7. 94, 7.21, 7.16, 6.97, 2.20, 1.77, 1.51. S3-955: 1 H NMR (400 MHz, CD2Cl2) δ = 7. 93, 7.22, 7.13, 6.96, 2.20, 1.79, 1.52. (Yield: 0.4 g, 20%). 84, 141.86, 136.27, 135.14, 129.66, 126.86, 116.57, 115.18, 106. 5.42 (d, J = 10.92 Hz, 1H). [START_REF] Wang | Computational Methods for Design of Organic Materials with High Charge Mobility[END_REF] C NMR (101 MHz, CD2Cl2) δ = 166. 14, 160.28, 142.01, 136.50, 135.63, 129.79, 127.06, 116.56, 115.49, 107.19, 62.53.

General process of polymerization of S4.

The polymerization of S4 is also a radical polymerization with 5% AIBN as initiator. Thus, the experimental conditions are the same ones as for S3 polymers.

Using 5A and 5B as monomers, the resulting S4 polymers are yellowish solids with conversions ranging from 33% to 45%. 8.22, 7.29, 7.09, 6.66, 6.17, 2.44, 1.93, 1.52. S4-991: 1 H NMR (400 MHz, CD2Cl2) δ = 8. 22, 7.28, 7.09, 6.64, 6.18, 2.43, 1.92, 1.52.

Appendix 3. Figures

Figure S2

The output and transfer characteristics of the as-prepared PBTTT-Tri transistor.

Abstract

In this work, new π-conjugated polymers were designed for the OFET and/or OLED applications.

First, two side-chain liquid-crystalline π-conjugated polymers, i.e. Polythiophene-oxa and PBTTT-Tri, consisting of π-conjugated backbones bearing side-on semiconducting mesogenic groups, were successfully prepared and their structures were determined by NMR, SEC, and elemental analysis. The thermal behavior and self-organization study indicated that Polythiophene-oxa and PBTTT-Tri can self-organize to lamello-lamellar and columnar-lamellar nanostructures, respectively. Moreover, both polymers exhibit p-type conduction.

Second, four families of new donor-acceptor (D-A) polymers were designed as potential TADF materials. Among them, two families are linear conjugated polymers, and the other two families are vinyl polymers with through-space conjugation (TSC). Their structures were also determined by NMR, SEC, and elemental analysis, and their photophysical properties were investigated. The results revealed that only S1, S2, and S4 series exhibit TADF character, among them, S4 polymers achieve the best performance, which is really encouraging. Anyway, their photophysical properties in blend films and electroluminescent properties will be investigated soon.