Rita Zakhia Douaihy

Houssein Nasrallah

Oleg Lebedev

Jaafar El Fallah

Rémy Guillet- Nicolas

Alexandre Vimont

Philippe Bazin
email: philippe.bazin@ensicaen.fr

Mohamad El-Roz
email: mohamad.elroz@ensicaen.fr

New approach for preparing zeolite-polymer hybrid materials with hierarchical porosity

Keywords: hybrid materials, zeolites, polymer, core-shell, dehydration

Here, we report a new approach for preparing zeolite-polymer core-shell like materials with hierarchical porosity via photopolymerization of trifunctional acrylic monomer (TMPTA) under UV-visible irradiation, using bifunctional Silane-based PhotoInitiator (SPI-1) as coupling agent. The free radicals, generated on the surface of zeolites, initiate the polymerization of the diluted monomers and therefore create an external and mesoporous polymer shell layer. The efficiency of the photopolymerization process and the textural properties of synthesized materials are investigated using different techniques including PXRD, TGA, UV-Vis, FTIR, SEM and TEM. The accessibility to the pores of the zeolite core are investigated by N 2 physisorption at 77 K and other probe molecules using IR spectroscopy.

Interestingly, the new approach is highly repetitive and reproducible and the accessibility to the zeolite's micropores is preserved with around 90 %. The newly synthesized hybrid materials show modified adsorption/separation capacities compared to the parent material toward water and ethanol adsorptions and during the dehydration of ethanol.

INTRODUCTION

In the last decades, mixed matrix membranes (MMMs) emerged to be excellent alternatives for polymeric and inorganic membranes [START_REF] Ebadi | Progress in Materials Science Substantial breakthroughs on function-Led design of advanced materials used in mixed matrix membranes (MMMs): A new horizon for efficient CO 2 separation[END_REF][START_REF] Jusoh | Current development and challenges of mixed matrix membranes for CO2/CH4 separation[END_REF] . This is due to their outstanding performance that exceeds Robeson's upper bound for gas separation [START_REF] Dechnik | Mixed-matrix membranes[END_REF][START_REF] Farnam | A Review on Glassy and Rubbery Polymeric Membranes for Natural Gas Purification[END_REF] . Their importance arises from the combination of the selective separative and adsorptive characteristics of the inorganic porous fillers and the mechanical and economical properties of the polymer matrices [START_REF] Castro-Muñoz | Progress on incorporating zeolites in matrimid® 5218 mixed matrix membranes towards gas separation[END_REF] . Different porous materials including zeolites [START_REF] Gong | Mixed-matrix membranes containing inorganically surface-modified 5A zeolite for enhanced CO2/CH4 separation[END_REF][START_REF] Liu | Preparation and characterization of S ilicalite-1/PDMS surface sieving pervaporation membrane for separation of ethanol/water mixture[END_REF][START_REF] Wu | Scale-up of zeolite-Y/polyethersulfone substrate for composite membrane fabrication in CO2 separation[END_REF] , silica nanoparticles 9 , MOFs [START_REF] Dechnik | Enhancing mixed-matrix membrane performance with metal-organic framework additives[END_REF][START_REF] Cheng | Ultrathin mixed matrix membranes containing two-dimensional metal-organic framework nanosheets for efficient CO2/CH4 separation[END_REF][START_REF] Elrasheedy | Metal organic framework based polymer mixed matrix membranes: Review on applications in water purification[END_REF] , COFs [START_REF] Kang | Mixed matrix membranes (MMMs) comprising exfoliated 2D covalent organic frameworks (COFs) for efficient CO2 separation[END_REF][START_REF] Shan | Mixed-matrix membranes containing an azine-linked covalent organic framework: Influence of the polymeric matrix on post-combustion CO2-capture[END_REF] , and others [START_REF] Sun | Fabrication of polyimide and functionalized multi-walled carbon nanotubes mixed matrix membranes by in-situ polymerization for CO2 separation[END_REF][START_REF] Molki | Mixed matrix membranes of polyurethane with nickel oxide nanoparticles for CO2 gas separation[END_REF][START_REF] Kononova | Polymer nanocomposite membranes[END_REF] were dispersed in the polymer matrix for gas separation [START_REF] Vinoba | Recent progress of fillers in mixed matrix membranes for CO2 separation: A review[END_REF][START_REF] Hamid | Recent advances on mixed-matrix membranes for gas separation: Opportunities and engineering challenges[END_REF][START_REF] Amooghin | Substantial breakthroughs on function-led design of advanced materials used in mixed matrix membranes (MMMs): a new horizon for efficient CO2 separation[END_REF][START_REF] Galizia | 50th anniversary perspective: polymers and mixed matrix membranes for gas and vapor separation: a review and prospective opportunities[END_REF] , permeation and water/alcohol purification [START_REF] Liu | Preparation and characterization of S ilicalite-1/PDMS surface sieving pervaporation membrane for separation of ethanol/water mixture[END_REF][START_REF] Elrasheedy | Metal organic framework based polymer mixed matrix membranes: Review on applications in water purification[END_REF][START_REF] Maghami | Zeolites-mixed-matrix nanofiltration membranes for the next generation of water purification[END_REF][START_REF] Castro-Muñoz | Mixed matrix membranes (MMMs) for ethanol purification through pervaporation: current state of the art[END_REF][START_REF] Kamelian | Fast, facile and scalable fabrication of novel microporous silicalite-1/PDMS mixed matrix membranes for efficient ethanol separation by pervaporation[END_REF] . Despite the divers applications of MMMs, the heterogeneous dispersion of the inorganic filler, the accessibility to its pores, and the undesirable defect between the organic matrix and the inorganic particles in addition to the non-homogeneous coverage are the common limitations emanating during the their synthesis [START_REF] Ebadi | Progress in Materials Science Substantial breakthroughs on function-Led design of advanced materials used in mixed matrix membranes (MMMs): A new horizon for efficient CO 2 separation[END_REF][START_REF] Wang | Advances in high permeability polymer-based membrane materials for CO 2 separations[END_REF] . To overcome these limitations, the polymer is treated either by its annealing above its glass transition temperature or by mixing it with a plasticizer to maintain its chain flexibility [START_REF] Maghami | Zeolites-mixed-matrix nanofiltration membranes for the next generation of water purification[END_REF][START_REF] Yang | Surface and interface engineering for organic-inorganic composite membranes[END_REF] . The inorganic filler can be thermally treated, or its surface can be modified by coating or grafted with integral chain linkers and silane-based coupling agents to assure better dispersion and promote the adhesion to the polymer matrix [START_REF] Maghami | Zeolites-mixed-matrix nanofiltration membranes for the next generation of water purification[END_REF][START_REF] Golemme | Surface modification of molecular sieve fillers for mixed matrix membranes[END_REF][START_REF] Maghami | Zeolite mixed matrix membranes (Zeolite-Mmms) for sustainable engineering[END_REF] . Moreover, the synthesis procedures reported in the literature could be classified in the following three main approaches [START_REF] Aroon | Performance studies of mixed matrix membranes for gas separation: A review[END_REF] : a) the polymer is added to a homogeneous suspension of inorganic particles, b) a predetermined quantity of inorganic particle is added to a homogeneous suspension of the polymer, or c) separate homogeneous suspensions of polymer and inorganic particles are mixed together. Nevertheless, the limitations previously mentioned were not completely surpassed via these approaches. Therefore, extensive work has been imputed to improve the synthesis of MMMs via radical or cationic photopolymerizationbased processes in the presence of a photoinitiator [START_REF] Bagheri | Photopolymerization in 3D printing[END_REF][START_REF] Corrigan | Seeing the light: advancing materials chemistry through photopolymerization[END_REF] .

Recently, a new approach has been validated by our group, where a MMM was synthesized by photopolymerization of an acrylate monomer on the surface of previously grafted silica nanoparticles with a silane-based photo-initiator [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF][START_REF] El Roz | Novel photoinitiators made from bifunctional silane[END_REF][START_REF] El-Roz | Radical and cationic photopolymerization: New pyrylium and thiopyrylium salt-based photoinitiating systems[END_REF] . Throughout this rapid and easy technique, and upon generation of free radicals on the surface of well-dispersed silica nanoparticles, a homogenous external layer of polymer is formed. The strong covalent bond between the silica particles and the polymer matrix resulted in a mixed membrane with enhanced mechanical properties. This synthesis procedure could be further conducted on other fillers such as zeolites.

To the best of our knowledge, few works on the photopolymerization of monomers with zeolites as seedings for MMMs have been reported [START_REF] Zhang | Photopolymerization of Zeolite/Polymer-Based Composites: Toward 3D and 4D Printing Applications[END_REF][START_REF] Xu | Effect of zeolite fillers on the photopolymerization kinetics for photocomposites and lithography[END_REF] . However, some limitations have been encountered such as the effect of the Si/Al ratio on the efficiency of the polymerization and the accessibility to the zeolite micropores that was only accessible after calcination and deterioration of the polymer layer. Thus, to surpass these limitations, we report here the synthesis of MFI-zeolite@polymer coreshell like structure, considered as a seeding for zeolite mixed matrix membrane. MFI nanoparticles are grafted with a previously synthesized silane-based photoiniator (SPI-1) by interactions between the silane groups of the zeolite and the ethoxy groups of the coupling agent. The grafted MFI nanoparticles are then tested in the free radical polymerization of diluted trimethylolpropane triacrylate (TMPTA). The obtained hybrid materials are then collected, purified and characterized using UV-Vis and IR spectroscopies and thermogravimetric analyses. Their morphologies are examined using SEM and TEM. The accessibility of the micropores in the zeolite-polymer hybrid materials are investigated using N 2 sorption and adsorption of probe molecules. Finally, the newly synthesized and the parent materials are tested in the preferential adsorption of ethanol, water, and water/ethanol mixture, a highly desirable process for bio-ethanol dehydration. The preferential adsorption is considered as an efficient and energy saving approach for purification of this mixture, since ethanol is always collected in an aqueous mixture and cannot be used directly as a biofuel or additive to gasoline.

EXPERIMENTAL

Materials: Industrial H-MFI zeolites provided by Clariant (formerly Süd Chemie, Si/Al= 45) were used in this work without any further treatment. Isobutyrophenone (IBP, 97 %), Allyl bromide (99 %), Potassium t-butoxide (99.99 %), tert-butanol (≥ 99.5 %), Diethyl ether (99 %), Sodium sulfate (99.99 %), Triethoxysilane (95 %), Dodecane (≥ 99%), Pt/Al 2 O 3 (5 wt%) and Trimethylolpropanetriacrylate (TMPTA) (technical grade) purchased from Aldrich, and Acetonitrile (AcN, 99 %) purchased from Alfa Aeasar, were used without any further purification.

Synthesis of 2,2-dimethyl-1-phenyl-5-(triethoxysilyl) pentane-1-one (SPI-1):

The synthesis of SPI-1 is detailed in the supporting information (Scheme S1 and Figure S1) and in reference 32.

Grafting of SPI-1 on the surface of the MFI zeolites (SPI-MFI):

1 g of MFI zeolites was dried at 150 °C and then dispersed in 10 mL of dodecane with 0.1 g of the previously synthesized SPI-1 under vigorous stirring for 20 minutes at 120 °C. The powder was collected by centrifugation and washed with acetonitrile (2 times) and several times with water and ethanol to remove the excess of the ungrafted SPI-1 and the solvent. The final precipitate is dried using a freeze-dryer before characterization. This procedure was repeated at least three times to check the repetition of the process and the reproducibility of the results.

Photopolymerization efficiency:

The capacity and the efficiency of the grafted SPI-1 on zeolite were investigated using IR spectroscopy by following the kinetic of the C=C bond conversion of the TMPTA monomer.

The conversion yield is calculated according to equation 1:

𝑪𝒐𝒏𝒗𝒆𝒓𝒔𝒊𝒐𝒏 ( % ) = (𝑨 𝟎 -𝑨 𝒕 ) 𝑨 𝟎 ⁄ * 𝟏𝟎𝟎 (equation 1)
where A 0 and A t correspond to the band area of the characteristic C=C stretching band of TMPTA at 1635 cm -1 at t = 0 and t = time of the photopolymerization, respectively.

The photopolymerizable samples were prepared by mixing the 1 wt.% of SPI- ). The bubbling and the stirring were maintained throughout the irradiation. After polymerization, the white precipitate was collected by centrifugation. Then, the excess of the monomer and the solvent were removed by washing with acetonitrile and water, respectively. The solid is then freeze-dried before characterization. The procedure was repeated at least three times to check the repetition of the process and the reproducibility of the results.

Characterization techniques:

The thermogravimetric analysis was recorded on a SETSYS analyzer (SETARAM) between 25 °C and 800 °C with a heating rate of 10 °C.min -1 under a flow of air (40 mL.min -1 ).

UV-Vis measurements were performed with a Cary 4000 (Varian) spectrophotometer in the spectral range between 200 and 400 nm. The spectrophotometer is equipped with a Praying Mantis diffuse reflection accessory.

PXRD patterns are recorded on a PANalytical X'Pert Pro diffractometer with an average Cu Kα radiation (λ = 1.5418 Å). The θ-2θ scans are recorded in the range of 2θ between 5° and 50° and a step size ~ 0.0167.

Nitrogen sorption isotherms at 77K were recorded using a Micrometrics ASAP 2020 volumetric adsorption analyzer. Before the measurements, the samples were degassed under vacuum at 150 °C, 180 °C or 200 °C for 12 hours. The specific surface areas are determined from the BET equation following the procedure recommended by Rouquerol et al. for microporous sorbents [START_REF] Rouquerol | Is the BET equation applicable to microporous adsorbents[END_REF] . The total pore volumes and the external surface areas are calculated from the t-plot method. Cumulative pore volume plots discussed in the SI were calculated via the VersaWin software 1.01 (Quantatec) using the adsorption branches of the isotherms and by applying the NLDFT kernel of (metastable) adsorption isotherms, considering an oxidic surface.

The morphologies of the parent and the modified samples were examined using electron microscopy. The SEM images were recorded using a TESCAN Mira field-emission scanning microscope at 20 kV. The TEM micrographs were recorded on a JEM200F cold FEG double aberration-corrected microscope equipped with a CENTURIO large-angle EDX detector. For SEM, the powder was dispersed on a thin layer of tin, fixed on carbon tape and the MFI powder was coated with platinum. Before TEM, the powder was dispersed in ethanol on a holey carbon film and coated with copper.

The pore accessibility and their acidity are investigated by in-situ IR experiments of pyridine and collidine adsorption on a ~20 mg self-supported pellets of the pressed powder (10 7 Pa/cm², S = 2 cm²). The spectra were recorded using an in-situ IR cell equipped with KBr windows connected to a Nicolet 6700 IR spectrophotometer, equipped with a DTGS detector and an extended-KBr beam splitter in the region between 400 and 5500 cm -1 (resolution 4 cm -1 , 128 scans) [START_REF] Zholobenko | Probing the acid sites of zeolites with pyridine: Quantitative AGIR measurements of the molar absorption coefficients[END_REF] . Before adsorption, MFI zeolites (MFI), MFI with grafted SPI-1 (SPI-MFI), and MFI with polymer (MFI@Polymer) were pretreated from room temperature to 150 °C (heating rate 2 °C.min -1 ) under vacuum (around 10 -5 Torr) for 1 hour in the IR cell connected to the vacuum apparatus. Pyridine and collidine adsorption were conducted at 150 °C. After establishing a pressure of 1 Torr at the equilibrium of each adsorbate, the cell was evacuated at 150 °C for pyridine, and at 100 °C for collidine to remove all physisorbed species.

Adsorption and coadsorption of ethanol and/or water:

The adsorption of water and ethanol, as well as their coadsorption at different relative pressures on MFI and MFI@Polymer, were performed using the AGIR technique [START_REF] Bazin | Interaction of water and ammonium in NaHY zeolite as detected by combined IR and gravimetric analysis (AGIR)[END_REF][START_REF] El-Roz | Pore Occupancy Changes Water/Ethanol Separation in a Metal-Organic Framework Quantitative Map of Coadsorption by IR[END_REF] . It couples the gravimetric analysis with IR spectroscopy to determine simultaneously the quantity of the adsorbed water and/or ethanol. The experiments were carried out on self-supported pellets (~ 20 mg, S = 2 cm²) and the samples were activated at 150 °C under a gas mixture of argon and oxygen (20 %) at 20 cm 3 .min -1 . The IR spectra were collected (64 scans at a resolution of 4 cm -1

, in the spectral region between 600 cm -1 and 6000 cm -1 ) using a Nicolet 6700 spectrometer outfitted with liquid nitrogen cooled MCT detector (mercury, cadmium, and tellurium detector). The mass of the sample and the corresponding spectra were recorded after reaching the equilibrium for each H 2 O, EtOH, or H 2 O/EtOH concentration. The stability at the equilibrium was detected by the absence of a change in the sample mass and in the intensity of the characteristic bands of ethanol (at 880 cm -1 ) and/or water (at 5275 cm -1 ). Additionally, the outlet flow was monitored by a mass spectrophotometer (Pfeiffer Omnistar GSD301) to ensure the steady state of H 2 O and EtOH in the gas phase.

RESULTS AND DISCUSSION

Grafting of SPI-1:

UV-Vis and FTIR spectroscopies: after grafting whereas the intensity of the bridged structural OH group (3610 cm -1 ) is hardly affected. This shows that the interactions between the zeolite and the SPI-1 are located on the outer surface of the crystallite [START_REF] El-Roz | Silicasilane reaction: Deciphering the silica-silane reaction mechanism for the development of a new generation of low rolling reistsnace tires[END_REF][START_REF] El-Roz | Infrared study of the silica/silane reaction. Part II. KGK Kautschuk[END_REF] , without affecting significantly the bridging OH groups. The decrease of the relative intensity of the bands -CH 3 at 2971 cm -1 and 1391 cm -1 respectively in the subtraction spectrum of SPI-MFI and MFI (Figure S2), validates also the grafting procedure through the ethoxy groups of the SPI structure.

SPI

Thermogravimetric analysis:

After grafting the silane-based photoinitiator SPI-1 on the surface of the MFI zeolites, the samples are subjected to thermogravimetric analyses (TGA) to determine the quantity of the grafted SPI-1 and to examine its thermal stability. The TG curves and their corresponding dTG

The efficiency of the grafted SPI-MFI in the photopolymerization of TMPA:

A photopolymerization kinetic study is performed thereafter to test the efficiency of the grafted SPI-1 on the MFI surface in the TMPTA photopolymerization under polychromatic and monochromatic (365 nm) irradiations conditions (Figure 2

Preparation and characterization of MFI@Polymer hybrid materials:

Based on the previous results, the preparation of the MFI@Polymer was performed by dispersing MFI-SPI in TMPTA/AcN solution under Ar atmosphere and polychromatic irradiation (Figure 3(A)). More details on the preparation of the hybrid materials can be found in the experimental part. After purification, the obtained MFI@Polymer powder is subjected to different characterization techniques including TGA, UV-Vis, and IR spectroscopy. The experiment was repeated several times and the error was estimated at around 10%.

Polymer loading in the MFI@Polymer hybrid material:

The sample is subjected to IR spectroscopy to investigate the formation of the polymer. The

Structural and textural properties:

After confirming the grafting and the polymerization processes, the crystal structure of the zeolite is examined using powder X-ray diffraction analysis. The PXRD patterns in Figure 4(A) indicate the preservation of the zeolite crystallinity after both grafting and photopolymerization processes.

Moreover, the porosity of synthesized hybrid materials is investigated using N 2 sorption at 77 K. The choice of the degassing temperature was made after a study conducted on MFI@Polymer at three different degassing temperatures: 150 °C, 180 °C, and 200 °C. The N 2 adsorption/desorption isotherms are represented in Figure S4 and Table S1. They show a significant decrease of the micropore volumes with the increase of the temperature. This It is worthwhile noticing that the SPI grafting and then the polymerization processes did not affect significantly the micropore volume of the MFI zeolites since more than 90 % of the micropore volume is preserved for MFI@Polymer material. This confirms that the polymerization occurs on the outer surface of the crystallite without affecting the accessibility of N 2 towards the zeolite micropores. By contrast, the external surface area significantly increases after polymerization suggesting that the polymerization process generates a supplementary mesoporosity confirmed by the presence of a H4-type hysteresis loop [START_REF] Thommes | Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report)[END_REF] . Of particular interest, for the MFI@Polymer, a sharp closure of the hysteresis loop is observed at P/P 0 = 0.4-0.5 during the desorption. This behavior is directly related with the so-called cavitation phenomena indicating that a substantial fraction of the pores only have access to the outer surface via opening/necks being smaller than ~ 5 nm, being very characteristic of coreshell materials [START_REF] Cychosz | Recent advances in the textural characterization of hierarchically structured nanoporous materials[END_REF] made from a mesoporous polymeric structure on the MFI zeolite,.

Additionally, the comparison between the NLDFT cumulative pore volumes of the MFI and MFI@Polymer (Figure S5) reveals no difference in the volume distribution between the two samples at small pore width (below 10 nm), confirming that the polymer grafting happens only on the external surface of the zeolites. The absence of the microporosity in the pure polymer confirms also that the microporosity in the hybrid material is solely coming from the core zeolites and is still accessible after the polymerization process. Considering the hydrocarbon content in SPI-MFI and MFI@Polymer, we can assume that the microporosity of the zeolite is highly preserved after both grafting and photopolymerization processes. The non-significant decreases of the porosity in both cases can be assigned to the covering/poisoning of the external acid sites or to a partial blockage of the porosity (lower than 20%). Further investigation of the samples' acidity will be presented later in this paper.

Morphological characterization:

The morphology of the MFI zeolites and the MFI@Polymer samples is then examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) (Figure 5).

The images in

Accessibility of the acid sites of the MFI in MFI@Polymer:

The accessibility of the acid sites of MFI zeolites (BAS (SiOHAl)), before (MFI) and after grafting (SPI-MFI) and polymerization (MFI@Polymer), is estimated upon adsorption of probe molecules: (i) pyridine that can be protonated by both internal and external acid sites and (ii) collidine, that specifically interacts with the external surface sites due to steric hindrance [START_REF] Thibault-Starzyk | 2D-COS IR study of coking in xylene isomerisation on H-MFI zeolite[END_REF][START_REF] Vimont | Analysing and understanding the active site by IR spectroscopy[END_REF] .

The resulting IR spectra are displayed in Figure 7 and correspond to the regions of the characteristic bands of each probe molecule. The band at 1547 cm -1 in Figure 7(A) is attributed to the pyridinium ions interacting with the BAS [START_REF] Vimont | Infrared spectroscopic study of the acidobasic properties of beta zeolite[END_REF] . For collidine, the bands situated at 1637-1645 cm -1 are characteristic of collidinium ions 49 (Figure 7(B)). The amount of adsorbed pyridinium and collidinium formed on the acidic sites was determined by integrating the area of their characteristic bands and using the following molar absorption coefficients: ε $%&' = 1.13 cm. µmol ($ 50 , and ε $)*' = 10.1 cm. µmol ($49 , respectively. The amount of BAS accessible to the two probe molecules in the three different samples are summarized in Table 2. The comparison of the amount of pyridinium (216 µmol. g -1 ) and collidinium species (17 µmol. g -1 ) detected on MFI shows that the proportion of Bronsted acid site located on the external surface is relatively low, about 9 % of the total number of BAS.

The comparison of the amount of pyridinium detected on the three materials clearly shows that more than 90 % of the Bronsted acid site remains accessible to pyridine molecules after both SPI-1 grafting and polymerization. Interestingly, these results agree with the preservation of the microporous volume determined by the N 2 sorption experiment. This demonstrates that the encapsulation method used in the present study conserved the Bronsted acidity of the core material in addition to the high permeability of the polymer towards pyridine.

The decrease of about 10 % of the total number of BAS in SPI-MFI and MFI@Polymer is mainly attributed to the significant decrease in the proportion of external Bronsted acid sites (more than 50 %). This is due to the poisoning or the disappearing of the outer BAS resulting from the grafting of the SPI-1 on the outer surface of the zeolite. The represented values with * and that with ** are normalized to the mass of zeolite (94 %) and (60 %), calculated by TG, respectively. The values between parentheses correspond to the percentage of the accessible sites compared to the parent zeolite.

Coadsorption of ethanol/water mixture on MFI and MFI@Polymer hybrid materials:

Water and ethanol adsorption capacities of MFI and MFI@Polymer:

After successfully synthesizing, characterizing the hybrid materials, and confirming the accessibility to the pores of the zeolites, the adsorption and separation capacities of the synthesized core-shell materials are tested for water, ethanol, and for ethanol/water mixture using the AGIR instrument. The evolution of the characteristic bands of ethanol at 880 cm -1 attributed to the C-C-O vibrations (ν ,(,(-) and 1450 cm -1 (𝛿 ,. ! ) and that of water at 1630 cm -1 (𝛿 . " -) and the combination band at 5270 cm -1 ((𝛿 + ν) . " -) was monitored using IR spectroscopy. However, in our case the characteristic band of ethanol at 1450 cm -1 (𝛿 ,. ! ) and that of water at 1630 cm -1 cannot be studied in the case of MFI@Polymer, due to their perturbation with a characteristic band of the polymer (δ (C-H) and ν ,/, , respectively). Since the coupling of the TG with the IR allows quantifying the adsorbed amount and the corresponding vibrational band area, respectively, the molar adsorption coefficient for the characteristic bands (ε (cm.µmol -1 )) of ethanol situated at ~880 cm -1 and that of water at ~5270 cm -1 for MFI and at ~5240 cm -1 for MFI@Polymer can be calculated (Figure S10). They allow later to determine the exact quantity of the adsorbed species once they are simultaneously present. The shift of the combination band of the molecular water on MFI@Polymer in respect to pure MFI (Δν = 30 cm -1 ) could reflect different configurations of adsorbed water and thus explains the difference between the values of the adsorption coefficients of the two materials. This shift might be explained by two hypotheses: the first one is that the external silanols on the zeolites of the MFI@Polymer sample are completely occupied by the polymer. Thus, the remaining active sites for water adsorption are the internal active sites in the pores of the zeolites. The second hypothesis is that the polymer is capable of adsorbing water by H-interactions between its carbonyl functions and water molecules. in the MFI@Polymer is filled with ethanol, slightly lower than that of MFI. Once the porosity of the zeolite is filled, the remaining ethanol is adsorbed on the mesoporous polymer.

Nevertheless, this trend is not observed for water (Figure 8(B)). The quantity of the adsorbed water in the zeolite micropores is low compared to the MFI zeolites and is not sufficient to fill its microporosity confirming the presence of a relatively hydrophobic barrier formed by the polymer around the MFI particles. However, the polymer demonstrates a capacity to interact weakly with water at relatively high partial pressure. The comparison between the water and the ethanol isotherms demonstrate that MFI have a good capacity to adsorb both water and ethanol, however MFI@Polymer's capacity to adsorb ethanol is much higher than that of water.

The main adsorption of water at the outer surface (probably via a weak hydrogen bond with the polymer carbonyl function) may explain the observed shift of the water vibration band and the 3 times higher extinction coefficient in respect to MFI. This result suggests the highly desirable behavior of the hybrid MFI@Polymer for ethanol dehydration.

Ethanol /water co-adsorption capacities of MFI and MFI@Polymer:

The coadsorption of ethanol/water mixture at RT is further studied on MFI and MFI@Polymer at a fixed water concentration and increasing ethanol partial pressure. First, a water partial pressure (P/P 0 = 0.3, 10000 ppm) is adsorbed on both samples and maintained constant. Once the equilibrium is reached, the gas flow is enriched with an increasing ethanol partial pressure.

The evolution of the IR spectra of MFI and MFI@Polymer during the coadsorption of ethanol/water mixture is represented in Figure 9((A)-(E)). Using the previously determined values of the molar adsorption coefficients, the quantities of adsorbed ethanol and water are calculated from the corresponding IR spectra (Figure 9(F)). The initial amount of adsorbed water on the MFI is greater than that adsorbed on MFI@Polymer, which is in accordance with the previous results of the pure adsorption of water. For MFI zeolites, at low ethanol partial pressure (P/P 0 < 0.1), water is strongly desorbed. With the increase of the vapor pressure of the ethanol, the quantity of desorbed water is increasing, simultaneously with the increase of the quantity of adsorbed ethanol. At P/P 0 > 0.3, the adsorption capacity of the zeolite is reached where a steady state of the amount of ethanol and desorbed water is observed. This might be explained by the high basicity of ethanol compared to H 2 O, that is being replaced on the acidic sites of the zeolite. A different trend is observed on MFI@Polymer. At P/P 0 of ethanol < 0.1, weakly adsorbed water molecules are replaced by ethanol. The remaining quantity not accessible for replacement on MFI@Polymer is greater than that on pure MFI (Figure S12).

Nevertheless, at higher pressures, the quantity of adsorbed H 2 O decreases slowly with the fast increase of the quantity of adsorbed ethanol. The residual adsorbed water is retained in the zeolite while ethanol is remained to be adsorbed on the polymer shell even at relatively high partial pressure, contrary to the MFI sample. This adsorption/desorption trend agrees with the previously discussed adsorption isotherms, where the modification of the surface engender higher ethanol adsorption capacity created in the mesoporosity of the polymer. Therefore, using the new synthesis approach it becomes possible to tune the hydrophobic/hydrophilic characters of the hybrid materials without modifying the core part, which can affect their adsorption capacity and their separation behavior.

  -1 was grafted on the surface of MFI zeolites via strong covalent interactions. The procedure is described in the experimental part. After grafting the SPI-1 on the surface of the MFI zeolites (SPI-MFI), the obtained samples are characterized by UV-Vis and in-situ transmission IR spectroscopies and compared to the MFI parent (Figure1). The UV-Vis of the grafted zeolite (spectrum (b) in Figure1(A)) displays new bands situated between 225 and 300 nm and at 325 nm, not observed for the parent zeolite (spectrum (a)). These bands are attributed to the 𝜋 -𝜋 * (225-300 nm) and 𝑛 -𝜋 * (325 nm) electronic transitions of the benzoyl groups of the SPI-1 structure[START_REF] Forbes | Light absorption studies: part XX. The ultraviolet absorption spectra and Infrared carbonyl bands of benzoyl chlorides[END_REF] .The reported IR spectrum in Figure1(B) of the SPI-MFI (spectrum (b)) displays the main characteristic bands of SPI-1: ν (CH) in the 3040-2700 cm -1 , ν (CO) at 1667 cm -1 , ν (CC) between 1580 and 1600 cm -1 and 1500-1350 cm -1 range assigned to the C=C stretching and CH deformation modes, respectively[START_REF] Thibault-Starzyk | 2D-COS IR study of coking in xylene isomerisation on H-MFI zeolite[END_REF] . The IR spectrum of MFI zeolite (Figure1(B) spectrum (a)) displays ν (OH) bands at 3743 and 3610 cm -1 attributed to silanol located on the outer crystallite surface and to structural bridged SiO(H)Al group respectively. The band at 3743 cm -1 totally disappears

  curves (Figure1(C) and (D)) reveal a first weight loss below 200 °C (at around 73 °C) for the two samples, which is attributed to the desorption of molecular water. The second weight loss in the SPI-MFI sample starting 180 °C to 800 °C with two peaks at 224 °C and 519 °C corresponds to the thermal degradation of the SPI-1 hydrocarbon. The total weight loss (around 9 wt.%) observed for the SPI-MFI sample is due to the loss of water (around 3 ±1 wt. %) and of SPI-1, which is estimated to be around 6 ±1 wt.%. The thermal stability of the SPI-1 structure is also investigated by IR spectroscopy under vacuum (10-6 torr). The evolution of the characteristic vibrational bands of the SPI attributed to the ν (CH) at different temperatures are reported in FigureS3. The results show a high thermal stability up to 180 °C with a low amount of physisorbed species (around 10 % of the total SPI quantity), which agree with the TG results.

Figure 1 :

 1 Figure 1: (A) UV-Vis and (B) FTIR spectra, (C) Thermogravimetric curves and (D) dTG of MFI ((a)-black) and SPI-MFI ((b)-red). The samples are activated at 150 °C before recording the IR spectra at RT. Inset (A): chemical structure of SPI-1.

  (A) and Figure 2(B), respectively).The evolution of the C=C of the TMPTA monomer is studied for SPI-1 (1wt%, curve (a)) and for 20 wt. % SPI-MFI (curve (b)). Freestanding polymer films are obtained for both samples under polychromatic UV irradiations.Under polychromatic UV irradiation (Figure2(A)), a decrease of around 20% in the conversion yield is observed when SPI-1 is grafted, which can be attributed to the shading effect of the inorganic filler on the absorbance of the SPI-1. On the other hand, under monochromatic irradiation (Figure2(B)), the conversion yield of the SPI dispersed in the monomer (curve (a)) (around 30 %) is lower than that obtained under polychromatic irradiation (around 55 %) attributed to a low absorption of SPI at 365 nm. This explains the choice of the polychromatic irradiation in further experiments. Similar behavior is observed for 20 and 30 wt.% SPI-MFI under monochromatic and polychromatic irradiations: a decrease in the C=C conversion yield compared to the pure SPI and an induction time of 20 seconds are observed under 365nm. This might be explained by the fact that the quantity of the quenchers is greater than that of the radicals in such irradiation conditions. As a conclusion, despite the impact of the zeolite on efficiency of the grafted SPI-1, this later still shows a high photopolymerization capacity under polychromatic irradiation, and the optimal filler:monomer ratio is around 1:2.

Figure 2 :

 2 Figure 2: Photopolymerization of trimethylolpropane triacrylate (TMPTA) under (A) polychromatic UV (Hg-Xe lamp) and (B) 365 nm (LED) irradiation using (a) 1 wt.% of SPI-1, (b) 20 wt.% of SPI-MFI and (c) 30 wt.% of SPI-MFI (correspond to 1.2 and 1.8 wt.% of SPI-1 equivalent, respectively). Photopolymerization condition: photopolymerization realized in laminated (air-free) condition (100 µm of thickness).

IR spectrum in Figure 3 (

 3 B) of the MFI@Polymer (spectrum (b)) shows the characteristic bands of the CH 2 -and CH 3 -groups of the polymer in the spectral region between 3040-2700 cm -1 and 1350-1480 cm -1 corresponding to the ν (C-H) and δ (C-H) respectively, the ν (C-C) of the alkene groups between 1650 cm -1 and 1540 cm -1 as well as the ν (C=O) at 1736 cm -1 . However, the relative intensity of the ν C=C band at 1650 cm -1 is very low confirming the high articulation of the polymers and the low content of terminal and unpolymerized function.The TG curves of the grafted SPI-MFI and the prepared sample (MFI@Polymer), as well as the corresponding dTG curves, are represented in Figure3(B) and (C). Similarly to the TG curve of SPI-MFI (Figure 3 (B) curve (a)), the TG curve of MFI@Polymer (Figure 3(B) curve (b)) reveals a first weight loss (around 4 wt.%) below 200 °C, attributed to the water desorption. Above 200 °C, the chemical and physical degradations of the polymer structure start as well as the degradation of the remaining anchoring group of the SPI-1. Thesedegradations are determined at the two-weight losses observed at 412 °C and 519 °C. The total weight loss is calculated around 44 wt.%. The quantity of the hydrocarbon loading in the MFI@Polymer sample is then determined to be around 40 ± 4wt.% (error estimated on three independent experiments). This result reveals a high polymer loading if we consider the low mass density of the hydrocarbon in respect to the filler (2 to 3 times lower than that of MFI).

Figure 3 :

 3 Figure 3: (A) Scheme of photopolymerization, (B) FTIR spectra, (C) thermogravimetric curves, and (D) dTG of SPI-MFI ((a)-black) and MFI@Polymer ((b)-red). The samples are activated at 150 °C before recording the IR spectra at RT.

  decrease could be explained by the physical change of the polymer with the increase of the temperature, making the polymers denser with the temperature around the zeolite particles and blocking partially the accessibility to the pores. Therefore, in all the coming experiments the activation temperature, when needed, is set at 150 °C. The N 2 isotherms at 77 K of MFI, SPI-MFI, MFI@Polymer and Polymer are represented in Figure4(B) and the corresponding NLDFT cumulative pore volumes are shown in FigureS5. The micropore volumes, the surface areas deduced from BET analysis, and the t-plot method are summarized in Table1. The measurements were conducted several times to ensure the reproducibility of the obtained results.

Figure 4 :

 4 Figure 4: (A) PXRD patterns and (B) N 2 adsorption/desorption isotherms at 77 K of MFI ((a)black), SPI-MFI ((b)-blue), MFI@Polymer ((c)-red)) and Polymer ((d)-green). The inset of (B) corresponds to zooming on the region of P/P 0 between 0.4 and 1. The adsorption/desorption isotherms of SPI-MFI ((b)) and MFI@Polymer ((c)) are offset vertically for clarification of 100 and 200 cm 3 /g, respectively.

Figure 5 (

 5 (A) and (C)) show that the pure zeolite sample is formed of agglomerated nanospheres of around 30-50 nm. After the photopolymerization process, these nanocrystals are covered by an opaque layer of the polymer (Figure5(B) and (D)). The SEM images didn't reveal the presence of any isolated polymer particles.

Figure 5 :

 5 Figure 5: SEM images (A and B) and TEM images (C and D) of MFI ((A) and (C)) and MFI@Polymer ((B) and (D)). The inset of (D) corresponds to a zooming on the polymer layer at the edge of the zeolites.

Figure 6 :

 6 Figure 6: (A) SEM image with EDX (O: green, Si: blue, C: red; scale = 2 µm) and (B) TEM images with EDX (O: blue, Si: green, C: red; scale = 50 and 20 nm) of MFI@Polymer.

Figure 7 :

 7 Figure 7: IR spectra of MFI ((a)-black), SPI-MFI ((b)-blue) and MFI@Polymer ((c)-red) before (dotted line) and after (solid line) (A) pyridine and (B) collidine adsorption. The inset of (A) corresponds to the subtraction spectra in the OH region. The spectra are collected after pyridine adsorption at 150 °C and after collidine adsorption at 100 °C and are normalized to the mass of the pellet (20 mg) and the mass of zeolite in each sample. The samples were previously degassed under vacuum at 150 °C.

Figure 8

 8 shows the gravimetric adsorption isotherms of adsorbed ethanol and water on MFI and MFI@Polymer. The isotherms are determined after measuring the recorded change in mass using the microbalance of the AGIR setup as a function of the increasing partial pressures of each adsorbate. The evolution of the corresponding IR spectra and the rise of the intensities of the corresponding vibrational characteristic bands are represented in Figure S11. Upon ethanol adsorption and after normalization to the mass of the zeolite (inset of Figure 8(A)), the microporosity of the zeolite

Figure 8 :

 8 Figure 8: (A) Ethanol and (B) water gravimetric adsorption isotherms on MFI ((a)-black) and MFI@Polymer ((b)-red). The adsorptions were conducted at RT. The insets figures correspond to the adsorbed quantities of ethanol and water after normalization to the mass of zeolite, determined from the TG (60 % of zeolites in the sample MFI@Polymer).

Figure 9 :

 9 Figure 9: (A) IR spectra of MFI (a) and MFI@Polymer (b) upon adsorption of ethanol/water mixture (P/P 0 C 2 H 5 OH = 0.013, P/P 0 H 2 O = 0.3). Evolution of IR spectra for characteristic bands of water ((B) and (C)) and ethanol ((D) and (E)) upon the coadsorption of ethanol/water mixture with increasing P/P 0 of ethanol from 0 to 0.65 on MFI@Polymer ((B) and ((D)) and MFI ((C) and (E)). The dashed-line spectra correspond to the spectra of the activated sample. (F) Variation of the quantities of adsorbed water ((a') and (b')) and adsorbed ethanol ((a), (b))on MFI (black) and MFI@Polymer (red) as a function of the partial pressure of ethanol (water concentration in the flow is fixed at 1%). The inset of (F) corresponds to the quantities on MFI@Polymer that are normalized to the mass of zeolite (60% of zeolite). The quantities of the adsorbates are determined from the areas of the characteristic bands of water at 5270 cm -1 and ethanol at 880 cm -1 .

Preparation of MFI@Polymer:

	Few drops of
	each mixture were spread on polypropylene films separated by a Teflon spacer (width = 100
	µm and diameter = 2 cm 2 ), and subjected to monochromatic (LED 365 nm, Irradiance (306.4
	mW/cm²)) and polychromatic UV irradiations (Xe-Hg lamp (LC8-01A spotlight, Hamamatsu,
	L10852, 200 W, I 0 ≈ 150 mW.cm -2 ).
	40 mg of the previously grafted MFI zeolites were dispersed in 20 mL of acetonitrile (AcN)
	via sonication. 80 mg of the TMPTA monomer were added to the solution in a transparent
	reactor. The overall mixture was bubbled with argon under stirring for at least 15 minutes and
	then subjected to polychromatic irradiation for 15 minutes using a polychromatic Xe-Hg lamp
	(LC8-01A spotlight, Hamamatsu, L10852, 200 W, I 0 ≈ 150 mW.cm -2

1 (used as reference) or the grafted SPI-MFI (1.8 and 3.6 wt.%) with TMPTA monomer.

Table 1 :

 1 Textural properties of MFI, SPI-MFI, MFI@Polymer, and Polymer tested by N 2 The represented values between parentheses are the raw values, without normalization to the mass of zeolite. Values with * and that with ** are normalized to the same mass of zeolite (94 %) and (60 %) respectively, based on the TG results.

	adsorption/desorption at 77 K.
				MFI	SPI-MFI	MFI@Polymer	Polymer
	S BET	a (m 2 /g)	413	378 * (355)	402 ** (241)	0
	External surface area b (m 2 /g)	83	101 * (95)	232 ** (139)	9
	Total (cm 3 /g)	Volume	0.420	0.415 * (0.390)	0.312 ** (0.187)	< 0.01
	Micropore volume c (cm 3 /g)	0.145	0.120 * (0.113)	0.133 ** (0.08)	0

a BET surface area, b,c t-plot.

Table 2 :

 2 Accessibility of MFI, SPI-MFI, and MFI@Polymer tested by adsorption of pyridine and collidine.

		MFI	SPI-MFI	MFI@Polymer
	n(µmol/g) Pyridine	216 (100 %)	187 * (93 %)	197 ** (92 %)
	n(µmol/g) Collidine	17 (100 %)	7 * (43 %)	9 ** (54 %)

Commented [ZR1]: change of numbering from A1-A2… to A-B-C-D

Funding Sources

This project is financed by European Union (3DZEOPOL project).

Notes

ACKNOWLEDGMENT

AUTHOR INFORMATION

Corresponding Authors

mohamad.elroz@ensicaen.fr philippe.bazin@ensicaen.fr

Author Contributions

The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

Authors acknowledge the Normandy region and European Union for the financial support (3DZEOPOL project). Rita Z.D acknowledges the Normandy region for the doctoral funding.


Houssein Nasrallah

Rita Zakhia Douaihy

Igor Telegeiev

Oleg I Lebedev

Armand Fahs

Mohamad El-Roz

New coupling agent structures for preparing fillerpolymer hybrid materials under soft-irradiation conditions

Keywords: Silane Based Photoinitiator (SPI), hybrid materials, silica, polymer, photolithography

The bifunctional coupling agents have become unavoidable products for preparing hybrid materials with enhanced properties. They are at the origin of the homogeneous dispersion of the filler in the polymerizable matrix and the strong chemical interactions between the composites during the thermal reticulation and vulcanization processes. However, only few structures can play this role in a photo-curable matrix, which is widely applied today in various manufactures (3D printing, cosmetic, medicine, etc.). Developing new structures capable of working under accurate irradiation conditions can extend the use of coupling agents for preparing hybrid photo-curable materials for various applications (e.g. membrane, masks, 2D-and 3Dnano/micro-objects). Recently, a new SPI (SPI-1) was proposed by our group and has revealed a high efficiency for preparing filler-polymer hybrid material. Despite its efficiency, its activity is the highest under the UV-B irradiation but lower under UV-A and inactive under visible light. In this paper, new coupling agent structures (bifunctional Silane-based Photoinitiators; SPI) are synthesized and tested under various irradiation conditions extensively used in the photocuring fields (365, 385 and 405 nm). All the new structures demonstrate higher performance than the first SPI generation (SPI-1) under the diverse light sources. More particularly, SPI-4, 5, and 6 (triphenylamine-based SPI) demonstrate a remarkable activity for preparing filler-polymer hybrid materials under visible light irradiation (LED 405 nm). The efficiency of the new structures in the photopolymerization as well as in the grafting of the silica particles (used as filler model) is elucidated. Finally, the enhancement of the mechanical properties of the hybrid composite films and the possible use of the new approach in photolithography is also demonstrated.

INTRODUCTION

Coupling agents have been widely used in the vulcanization processes [START_REF] Wang | Reinforcing Behaviors of Sulfur-Containing Silane Coupling Agent in Natural Rubber-Based Magnetorheological Elastomers with Various Vulcanization Systems[END_REF] and thermal polymerization [START_REF] Pan | Improved thermal conductivity and dielectric properties of hBN/PTFE composites via surface treatment by silane coupling agent[END_REF][START_REF] Wu | In situ polymerization of modified graphene/polyimide composite with improved mechanical and thermal properties[END_REF] . Their importance has risen from the dual types of their functional groups: one interacts with the organic matrix and one is attached to the surface of the inorganic filler 4, 5. They enhance the interactions between the inorganic fillers and the polymer matrix by preventing the agglomeration and the formation of clusters and assuring a homogeneous dispersion [START_REF] Kahraman | Synthesis of a novel bifunctional photoinitiator: hybrid coatings on polycarbonate[END_REF] .

Additionally, they improve the interfacial adhesion and therefore the stability and the mechanical behavior of the formed hybrid materials with respect to the fillers-free polymer [START_REF] Buestrich | ORMOCER® s for optical interconnection technology[END_REF][START_REF] Kahraman | The novel use of organo alkoxy silane for the synthesis of organic-inorganic hybrid coatings[END_REF] . Lately, light induced polymerization has been extensively developed since it can occur under mild conditions, in the absence of organic solvent and at room temperature with excellent spatial and temporal control [START_REF] Dietlin | Photopolymerization upon LEDs: New photoinitiating systems and strategies[END_REF][START_REF] Zhang | Radical photoinitiation with LEDs and applications in the 3D printing of composites[END_REF][START_REF] Layani | Novel materials for 3D printing by photopolymerization[END_REF] . Photocuring materials have consequently gained great interest since they can be used in the daily consuming [START_REF] Zhao | Recent advances in functional 3D printing of foods: A review of functions of ingredients and internal structures[END_REF] , electriconics [START_REF] Mendes-Felipe | State-of-the-art and future challenges of UV curable polymer-based smart materials for printing technologies[END_REF] and biomedical products [START_REF] Zheng | Visible light-induced 3D bioprinting technologies and corresponding bioink materials for tissue engineering: A review[END_REF][START_REF] Xu | Vat photopolymerization 3D printing for advanced drug delivery and medical device applications[END_REF][START_REF] Kessler | 3D printing in dentistry-state of the art[END_REF] . Inspired foremost by the role of the coupling agents, the development of new photoactive and bifunctional coupling agents for the photopolymerization is therefore highly required.

In this context, several coupling agents were developed to enhance the properties of the photocuring materials under UV irradiation such as titanate [START_REF] Elshereksi | Review of titanate coupling agents and their application for dental composite fabrication[END_REF][START_REF] Wang | Functionalizing graphene with titanate coupling agents as reinforcement for onecomponent waterborne poly (urethane-acrylate) anticorrosion coatings[END_REF] and silane [START_REF] Ahangaran | Recent advances in chemical surface modification of metal oxide nanoparticles with silane coupling agents: A review[END_REF][START_REF] Shokoohi | Silane coupling agents in polymer-based reinforced composites: a review[END_REF][START_REF] Provost | Influence of silane coupling agent on the properties of UV curable SiO2-PMMA hybrid nanocomposite[END_REF][START_REF] Liu | Preparation of UV curable organic/inorganic hybrid coatings-a review[END_REF] . Among them, a new bifunctional silane-based photoinitiator coupling agent (SPI-1) has been developed recently by our group [START_REF] El | Igor New photoinitiator based on bifunctional silane[END_REF][START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] which ensures strong covalent and chemical interactions between the filler particles and the polymer matrix [START_REF] Blume | Infrared study of the silica/silane reaction. 11 Kautschuk Herbst Kolloqium[END_REF][START_REF] El-Roz | Infrared study of the silica/silane reaction. Part II. KGK Kautschuk[END_REF] . Upon UV irradiation, ketyl radicals are engendered on the surface, initiating the polymerization of the acrylate monomer. Thus a homogeneous external polymer layer is obtained on the surface of the silica nanoparticles, creating therefore a hybrid material with enhanced mechanical properties. [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] However, SPI-1 demonstrates activity only under UV-B irradiation and is inactive under visible light. If the synthesis of photocuring materials under UV light irradiation achieved great interest, some safety concerns have risen from its use including eye and skin damages in addition to associated consumption and energy cost [START_REF] Yoshino | Effects of blue-light irradiation during dental treatment[END_REF][START_REF] Ibrahim-Ouali | Recent advances on chalcone-based photoinitiators of polymerization[END_REF] . Thus, 3D-printing systems are modified and adapted to work under near-UV-A (>350 nm) and visible-light irradiations (>390 nm).

To the best of our knowledge, only one photoactive coupling structure with dual activity, inspired from our previous work [START_REF] El | Igor New photoinitiator based on bifunctional silane[END_REF][START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] , has been very recently synthesized and studied for photopolymerization under visible light irradiation [START_REF] Peng | Visible-Light-Sensitive Triazine-Coated Silica Nanoparticles: A Dual Role Approach to Polymer Nanocomposite Materials with Enhanced Properties[END_REF] , where a commercial triazine photoinitiator has been silylated, in order to attach the silane functional groups.

Based on the market needs to develop photoinitiator coupling agents active in the visible region and based the promising advantages of the previously synthesized silane based photoinitiator, we aim in this work to widen the efficiency range of the previously synthesized SPI so it can be active under different visible irradiations, considering the cost effective of the proposed structure. The approach consists on the substitution of phenyl group of SPI-1 by near-UV/Visible responsive aryls while conserving the same linear alkyl-silane group. Thus, thioanisole, pyrene and mono-, di-and tri-substituted triphenylamine based photoinitiators SPI-2, -3, -4, -5 and -6 were synthetized, respectively. The efficiency of the new SPI structures is tested in the polymerization of trimethylolpropane triacrylate (TMPTA) under different light sources mostly used in the photocuring technology and commercial public equipment (as 3D-printers): LED 365 nm, LED 385 nm and LED 405 nm. The behaviors of the excited states of the synthesized SPIs are investigated by time-resolved absorption transient spectroscopy. Later, the efficiency of a selected SPI (SPI-4) and grafted on the surface of silica nanoparticles, is characterized and tested in the polymerization of TMPTA, and compared to that of the grafted SPI-1. Finally, dispersed SPI-4 in TMPTA is tested in photolithography using an ink-jet printed mask on transparent film in order to test the spatial resolution of the process and study the mechanical properties of the composites.

RESULTS AND DISCUSSION

SPI-X synthesis and characterization

The synthesis of SPI-1 was reported in our previous work starting from isobutyrophenone (Scheme 1) [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] . Inspired from this successful and relatively cost-effective approach, a series of new structures (called SPI-X; with X =2, 3, 4, 5 and 6) was prepared in the same general synthetic pathway with an additional electrophilic aromatic substitution (EAS) of aryl groups with the isobutyryl group using AlCl 3 . The SPI's precursors (P-SPI-X) were then obtained via a subsequent treatment with allyl bromide in a basic medium to introduce the allylic group. To obtain the new structures, triethoxysilane anchoring group was added to the precursors (P-SPI-X) by a platinum catalyzed anti-Markovnikov hydrosilylation using 5 wt.% of Pt on Al 2 O 3 catalyst. In the first step (step 1 in Scheme 1), the compounds P-1-SPI -2 and -3 were isolated starting from thioanisole and pyrene with yields of 99% and 77 %, respectively. However, to prepare P-1-SPI -4, -5 and -6, a controlled mono-, di-, and tri-electrophilic aromatic substitution of triphenylamine was realized by adjusting the quantity of the isobutyryl chloride (IBC) and that of the AlCl 3 as well as the temperature of the reaction. This optimization allowed isolating P-1-SPI -4, -5 and -6 with 61, 66, and 63% yields, respectively. Subsequently the allylation (step 2) was realized by introducing 3 equivalents of allyl bromide for each isobutyryl group to obtain the P-SPI -2, -3, -4, -5 and -6 precursors with satisfactory yields (62-80%). Finally, for the hydrosilylation (step 3), two equivalents of HSi(OEt) 3 were introduced for each allyl group to obtain the SPI -2, -3, -4, -5 and -6 structures with yields of 31, 26, 21, 11 and 18 %, and overall yield of 24, 13, 10, 5 and 7%, respectively. The relatively low overall yields are originated essentially from the hydrosilylation step where unidentified by-products with ratio of 50% are obtained. This selectivity issue is due to the heating requirement at 83°C with heterogenous Pt/Al 2 O 3 catalyst during the hydrosilylation to achieve higher conversion. Nevertheless, the heterogenous Pt/Al 2 O 3 was able to be recycled by filtration and was successfully tested for 3 efficient to obtain SPI-1 in 60 g scale. On the other hand, the yield of SPI -4, SPI -5, and SPI -6 can be significantly enhanced if their corresponding precursors are not separated where mixtures of SPI-4/SPI-5 and SPI-5/SPI-6 will be obtained, respectively. The mixtures will not affect their roles as coupling agents for real applications.

However, in this study, the separation was required in order to investigate separately the properties of each structure. The purity of all SPI was always higher than 90% except for SPI-6 (estimated purity of 70%) due to the difficult separation step from the unidentified by-product. The low overall yield of SPI -4, -5 and -6 can be enhanced by using homogeneous catalyst (e.g. [IrCODCl] 2 [START_REF] Xie | Iridium-catalyzed hydrosilylation of unactivated alkenes: scope and application to late-stage functionalization[END_REF] , Ru-based catalyst [START_REF] Glaser | Catalytic hydrosilylation of alkenes by a ruthenium silylene complex. Evidence for a new hydrosilylation mechanism[END_REF] ) in the anti-Markonikov hydrosilylation limiting step and minimizing therefore the by-product due to the use of Pt/Al 2 O 3 catalyst at 80°C. However, these catalysts are highly sensitive toward oxygen and moisture and their manipulation should be conducted in inert conditions making the process less costly despite the higher overall yield. In addition, contrary to the heterogeneous Pt/Al 2 O 3 which it was recycled and can be used at least for three cycles, the homogeneous catalyst cannot be recycled increasing furthermore the cost of the process. Detailed synthesis procedures, synthesis conditions and NMR spectra of the new structures are given in the supplementary information SI (Figure S1-Figure S27). Scheme 1. Illustration of the synthesis approaches of the various SPI structures studied in this work.

After successfully synthesizing the different SPI structures, they were characterized using UV-Visible spectroscopy to determine their optical and electrochemical properties. The molar extinction coefficient for every structure is determined using the Beer-Lambert law (Figure 1).

The characteristic band attributed to the electronic transition of the 𝜋 -𝜋 * of the benzoyl group is observed in all the UV-Vis spectra of the different SPI structures, in the region between 225 and 300 nm [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] . Additionally, the characteristic band of the electronic transition of the 𝑛 -𝜋 * of the benzoyl group is observed for SPI-1 and SPI-2 at 300 nm. Particularly, for SPI-2, the characteristic band of the thioanisole group ( 𝜋 -𝜋 * ) at 250 nm is observed [START_REF] Li | Computational simulation and interpretation of the lowlying excited electronic states and electronic spectrum of thioanisole[END_REF] . The electronic transitions of the pyrene structure of the SPI-3 are observed in the region between 250 and 380 nm [START_REF] Gališinová | A Study of Local Anaesthetics. Part 202. Determination of the Critical Micellar Concentration of Carbisocainium Chloride in Water Using Spectral Methods and the Probe Pyrene[END_REF] , whereas the electronic transition of 𝑛 -𝜋 * in of the SPI -4, -5 and -6 structures are detected between 300 and 400 nm. [START_REF] Hou | Stable hole-transporting molecular glasses based on complicated 9, 9-diarylfluorenes (CDAFs)[END_REF] As investigated, all new structures illustrate a significant redshift in respect to the previous SPI-1 structures. More particularly, SPI -4 to -6 demonstrate a promising overlap of their absorbance with the light emission of the various LED irradiations (Figure 1) frequently used in the lithography and the 3D-photoresine's printers. It should be noted that SPI and P-SPI structures show similar light absorbance profile and therefore siloxane group has no impact on the photochemical behaviors of the SPI.

Photopolymerization efficiency of the new structures

The activity of the SPI structures (1-6) in the radical photopolymerization of TMPTA using three different light sources (LED 365 nm, 385 nm and 405 nm) is examined by real time IR spectroscopy analysis (Scheme S1). Due to the relatively low purity of SPI-6, the P-SPI-6 is used after confirming that the precursor and its corresponding structure have similar photopolymerization performances by comparing SPI-4 with P-SPI-4 under monochromatic irradiation (365 nm) (Figure S28). The kinetics of photopolymerization process was determined by monitoring the evolution of the C=C vibration band (at 1635 cm -1 ) of the TMPTA monomer using IR spectroscopy and the results are assembled in Figure 2 (A-F). The apparent photopolymerization rate (Rp) and the conversion yields are summarized in Table S2.

Under the various irradiation sources, SPI-1 showed the lowest performance compared to the new SPI structures, with a maximum conversion of 36 % under 365 nm. An induction time (around 20 seconds) is observed for SPI-2 and SPI-3 under 365 nm, with a relatively higher conversion for SPI-3 (39% vs 51%, respectively). The induction time might be explained by the insufficient quantity of the radicals compared to the quantity of the quenchers (e.g. dissolved oxygen, etc.) in the first few seconds of the reaction. The efficiency and the conversion yields of SPI -2 and -3 are dramatically affected under 385 nm and 405 nm. However, SPI-4 shows the highest activity under the various irradiation condition as a mono-silane functionalized structure. These results are in good agreement with the absorbance of the SPI-4 structure.

The activity of the mono-, di-and tri-substituted triphenylamine based SPI is compared under the same previous conditions (Figure 2, D-F). All of them showed good efficiency with TMPTA conversions higher than 30 % with the highest conversion yield for SPI-6 (P-SPI-6). Nevertheless, only SPI-4 will be considered in our study due the synthesis issue encountered in the preparation of SPI-5 and -6 (lower yield and purity, respectively).

Absorption transient of the SPI-X excited states

The time resolved absorption transient spectroscopy shed more light on the behavior of the excited state of the different SPI structures (Figure 3). SPI-1 demonstrates an absorption transient (AT) band centered at 650 nm which corresponds to the absorption of the triplet state of the SPI-1. The SPI -2's and -3's AT-spectra reveal two maxima each at 640, 530 nm and at 460, 430 nm, respectively, revealing an impact of the substation group on the photochemical behavior of the excited state. The AT spectra of the SPI -4, -5 and -6 show low red-shift in respect to SPI-1, with a significant red-shifted bleaching at 340, 350 and 355 nm, respectively. In addition, a residual absorbance with relatively long lifetime could be observed in the visible range (except for SPI-3) and probably corresponds to the absorption of the relatively stable benzoyl radicals. It should be noted that the bleaching of SPI -4, -5 and 6 follows an increasing order and confirms the increase of the relative quantum yield with the structure substitution of the triphenylamine. S3) assemble the decay (and the absolute lifetime) of the excited state versus time at the corresponding maximum of the absorption transient for each structure (Figure 3). The results show a fast quenching of SPI-3 with respect to the other SPI without any residual absorbance. This could be the main reason of the relatively low activity of this structure. However, SPI-1 demonstrates similar kinetic decay of the excited state in comparison with SPI -2, -4, -5 and -6. Therefore, the highest activity is mainly related to their highest absorbance. Nevertheless, it is complicated to reveal with precision the origin of the activity of the new structures as many factors can contribute to the global activity (quantum yield of the different process and activity of the generated radicals). In addition, all structures show high sensitivity toward oxygen with a constant rate of oxygen quenching 3 to 7 10 9 M -1 s -1 (Table S3), which require an oxygen-free photopolymerization process. It is important to mention that the new structures are well designed in a way that the allyl radicals are always attached to the grafted surface, ensuring then an efficient initiation of the polymerization process, and therefore the efficiency of the shell formation around the particle is not altered by the stability of the chromophore/benzoyl radical moiety (due to the increase of the rearrangement with the conjugated bond). This justifies our initial choice to avoid the grafting of the siloxane grafting function on the benzoyl moiety of the SPI structures. (4), SPI-5 (5), and SPI-6 (6). The spectra were registered at the 𝜆 max of the absorption transient of the different SPI-structures (Figure 3). The negative region due to the photoluminescence of the products.

Grafting of SPI-1 and SPI-4 on silica nanoparticles

Based on the previous results, only SPI-4 and SPI-1 (used as reference) are considered for studying their efficiency in the grafting process of silica nanoparticles (used as filler) and the efficiency of the grafted filler for preparing silica polymer hybrid materials. The grafted silica samples with SPI-1 and SPI-4 are firstly characterized using thermogravimetric analysis (Figure 5(A)) to quantify the amount of the grafted SPI. A higher weight loss of the grafted silica in comparison to the parent silica (ref) is reported. The evaporation of adsorbed water on the surface of silica particles cause a weight loss at temperatures below 200 °C in all cases. The weight loss below 300 °C for the grafted silica nanoparticles is attributed to the degradation of SPI structure.

The weight loss from 300 to 700°C can be accredited to the thermal decomposition and the total oxidation of chemical-bonded groups on the surfaces, as well as to the condensation process of the vicinal silanol groups (the silica dehydration from this process is estimated to be less then 1 wt.% as observed on the pure silica (ref)). Thereby, the results indicate that both SPI-1 and SPI-4 are chemically bonded to the silica surface with a loading of 2.55 ±0.05 and 3.1 ±0.05 wt.%, respectively. The higher amount of grafted SPI-4 is mainly assigned to the higher molar mass of this later with respect to the SPI-1. S4 in the SI. The disappearance of the isolated silanol groups at 3744 cm -1 after grafting of SPI-4 (Figure S29) confirms that the grafting mechanism is similar to that previously reported. [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF][START_REF] El-Roz | Infrared study of the silica/silane reaction. Part II. KGK Kautschuk[END_REF] In contrast to the solvent-based chemical grafting, which has several significant technological and environmental disadvantages [START_REF] Telegeev | Modification of Nanosilica Surfaces by Methyl Methacrylate Oligomers[END_REF] , dry surface functionalization is considered more environmentally friendly, since it is occurs in the absence of a solvent [START_REF] He | Surface modification of fumed silica by dry silanization for PPbased dielectric nanocomposites[END_REF] . The TGA and FTIR spectra illustrating the difference in modified nanosilica, prepared by the two different grafting methods are reported in Figure S30 and Figure S31 in the supplementary information. The results reveal uniform distribution and similar loading of silane with both methods indicating the unnecessary excessive use of solvent for grafting the SPI compounds. The thermal stability of silica_SPI-4 is investigated using in-situ FTIR under vacuum conditions (10 -5 torr). The evolution of the IR spectra of silica_SPI-4 is reported in Figure 5(E) and the evolution of the vibration band at 1390 cm -1 characteristic of grafted SPI -1 and -4 at different temperatures is reported in Figure 5(F). The results show a low amount of physisorbed species (decrease from 125-225 °C ~ 8 % from the overall SPI amount) with a relatively high thermal stability (until 225 °C) of the residual species for both structures. These results agree with the results obtained from the TG analysis and demonstrate that the chemically grafted SPI is ranging between 92 and 95% of the total SPI content in silica_SPI -1 and -4, respectively. Thus, the mechanism of grafting can be determined by the covalent bonds between the alkoxy groups of SPI and isolated silanol groups of the silica occurs via the formation of new Si-O-Si bonds and the release of alcohol molecules.

Preparation of silica@polymer hybrid materials using SPI -1 and -4

Moreover, the viscosity of the UV curable dispersion is a key parameter which needs to be considered in order to control UV-curing kinetics as well as the processability of the system. It typically reveals particle-particle and particle-monomer interactions. The viscosities (measured at shear rate of 100 s -1 ) as a function of grafted nanosilica content in TMPTA monomer mixtures are represented in Figure 6. As could be expected, the viscosity of the TMPTA filled with grafted silica nanoparticles displays the lowest value compared to that with ungrafted silica and increases with the increase of the filler content. This is due to the agglomeration of ungrafted nanoparticles yielding highly viscous dispersion due to the presence of silanol groups on the silica surface (Figure 5(D)). On the contrary, the modified silica nanoparticles have shown an improved compatibility with TMPTA, due to the formation of the organic shell of SPI and the decrease of the silanol content on the nanosilica surface. This leads to the enhancement of the hydrophobic/hydrophilic interactions of the dispersion medium and the dispersion phase. The viscosities of the formulations containing modified nanosized silica (grafted with equimolar amount of SPI -1 and -4) reveal some differences at shear rate of 100 s -1 which could be assigned to a higher polarity of the SPI-4. As a consequence, 25 wt. % of silica_SPI -1 and -4 dispersed in TMPTA was chosen as appropriate filler loading. At this loading, photoinitiator content can sufficiently initiate photopolymerization process, while maintaining an appropriate viscosity for stereolithography applications (up to 10 Pa.s for 100 s -1 in 26 °C 37 ). and (C)). Accordingly, the kinetics of polymerization decrease after grafting SPI on the surface of silica nanoparticles. This might be due to the presence of the silica particles that hinders the movements of the polymer chains and/or causing a shading effect. At the same time no significant difference between the final conversion yields is revealed according to SPI/TMPTA photopolymerization results. Thus, silica_SPI-4 shows a high conversion yield (45 %) under irradiation at 365 nm with a decrease to 39 % at 385 nm and to 33 % at 405 nm. However, silica_SPI-1 shows low activity under 365 nm irradiation with a conversion yield of 30 %, in agreement with the activity of the pure SPI-1 structure (Figure 2). These results indicate that the activity of the new SPI-4 structure is not altered by the grafting process which is very promising for preparing hybrid materials under soft irradiation conditions. We should mention that the choice of the TMPTA as monomer is due to its desirable viscosity for both photopolymerization (homogeneous and hybrid). However, SPI -1 and -4 were also tested in the photopolymerization of the di-ethylene glycol di-acrylate (DEGDA, bifunctional acrylate) and methacrylate (MA, monofunctional acrylate) monomers. The results are assembled in Figure S33 and Figure S34, respectively, and demonstrate that SPI-4 presents always higher activity than SPI-1 under various irradiation conditions for polymerizing acrylate-based monomers (mono-, bi-and tri-acrylate). It should be noted that the induction time observed in the case of MA is probably assigned to a higher quenching of the SPI triplet state by the monomer and/or dissolved oxygen (more significant at lower viscosity).

washing the polymerized film, the none photopolymerized part was easily removed via a sample wash with ethanol (Figure 8) demonstrating that the photopolymerization occurred selectively in the irradiated zones and that the hybrid silica-polymer can be spatially controlled as in the case of a conventional photopolymerizable systems. The SEM images demonstrate an interesting spatial resolution and the EDX mapping shows a homogeneous dispersion and embedded of the silica filler in the polymer matrix. It should be noted that the deterioration of some the letters is happing during their transfer from the polymer support to the SEM-support. Finally, the mechanical properties of the composites' films prepared using SPI-4/silica were performed using atomic force microscopy (AFM) [START_REF] Bv | Effect of contact deformations on the adhesion of particles[END_REF][START_REF] Muller | On two methods of calculation of the force of sticking of an elastic sphere to a rigid plane[END_REF] . Three films with a thickness around 50 µm were prepared under 385 nm for 5 min from three photopolymerizable formula: TMPTA+P-SPI-4 (pure polymer), TMPTA + P-SPI-4 + ungrafted silica and TMPTA+Silica-SPI-4. The results are assembled in Figure 9 and show the AFM topographic and mechanical maps obtained for pure photopolymer film, and of the composites' films prepared in presence of ungrafted silica and by using silica-SPI-4. Smooth surfaces with roughness lower than 1 nm were demonstrated by the topographies of the surface of all films. Interestingly, the composite film prepared with SPI-4/silica nanoparticles shows nanodomains (≈50 nm) having high elastic modulus, associated to the silica nanoparticles. For the film prepared in presence of ungrafted silica (using P-SPI-4 as photoinitiator), aggregations of silica nanoparticles are most likely localized into the bulk of the film. These results are in agreement with our previous work obtained with SPI-1. [START_REF] Douaihy | Synthesis of silica-polymer core-shell hybrid materials with enhanced mechanical properties using a new bifunctional silane-based photoinitiator as coupling agent[END_REF] They demonstrate an enhancement of the mechanical properties of the composites once silica-SPI are used as photoinitiator fillers. The elastic modulus of the silica-SPI/Polymer composites is found to be 2 to 3 times higher compared to the pure polymer, or composite prepared with ungrafted silica. This increase is mainly assigned to the high dispersion and homogeneous silica nanoparticles and their chemical connection with the polymer matrices. mechanical maps (middle, z scale 4 GPa) and the corresponding histograms (bottom) of pure polymer (left), composite prepared with ungrafted silica (middle) and with silica-SPI-4 fillers (right). The light areas in the elastic modulus correspond to a higher rigidity of the analyzed zone and the white dotes nanodomain (≈50 nm) observed in the EM for the silica-SPI-4-Polymer film assigned to the highly dispersed silica nanoparticles near to the surface. Z-scale of the EM is identical for all images.

CONCLUSION 2D Topography

Elastic modulus (EM) of the SPI-X on the silica and the photopolymerization procedure; photopolymerization kinetic of P-1-SPI-4 and SPI-4; table summarizing the polymerization rates; the lifetime of the triplet excited states; characteristic vibrational bands; comparison between the two grafting methods;

and the conversion yields at different silica_SPI-4 loadings and photopolymerization kinetics of di-ethylene glycol di-acrylate and methacrylate using SPI-4 and SPI-1 .

For Table of Contents Only

Figure 1 .

 1 Figure 1. UV-Visible spectra of different SPI structures and spectrum of the different LED lights

Figure 2 .

 2 Figure 2. Photopolymerization kinetics of trimethylolpropane triacrylate (TMPTA) under (A) 365

Figure 3 .

 3 Figure 3. Evolution vs the time (1 𝜇s/spectrum) of the absorption transition (AT) of SPI-1 (1),

Figure 4 (

 4 Figure 4 (and TableS3) assemble the decay (and the absolute lifetime) of the excited state versus

Figure 4 .

 4 Figure 4. (A) Normalized kinetic decay traces of the triplet excited state of SPI-1 (1), SPI-2 (2),

Figure 5 .

 5 Figure 5. (A) TG, (B) dTG, (C), UV-Vis spectra, (D) IR spectre (E) Evolution of the FTIR spectra

Figure 6 .

 6 Figure 6. Evolution of the viscosity of the TMPTA with the amounts of the fillers: (ref) pure (non-

Figure 8 .

 8 Figure 8. (A) Optical and (B) SEM images of the polymer-silica films after photopolymerization

Figure 9 .

 9 Figure 9. The AFM 2D-topographic images (top) at 5x5 µm scale, the elastic modulus (EM)

To test the possible spatial resolution of the photopolymerization once silica_SPI-4 is used as photoactive filler, a homemade printed mask has been used to limit the light transmittance (405 nm) to the desired zone. The images of the corresponding films are reported in Figure 8. After Five new bifunctional coupling agent structures have been synthesized form three steps synthesis pathway using recyclable heterogeneous Pt/Al 2 O 3 catalyst and tested for preparing filler-polymer hybrid materials. The triphenylamine based structures (SPI-4 to 6) showed the highest activity under the various irradiation conditions going from UV-B to the visible light. Particularly, the cost-effective SPI-4 structure can be easily scaled up and therefore it is considered as promising candidate for preparing hybrid material by photopolymerization under soft irradiation condition.

The activity of the SPI-4 was tested in the photopolymerization of mono-(MA) bi-(DEGDA) and tri-(TMPTA) functional acrylate-based monomers and compared to that obtained with SPI-1. A higher activity of SPI-4 under the various irradiation conditions (365nm, 385 nm, and 405 nm) was obtained and mainly assigned to its high absorbance of light (higher quantum yield) with similar activity of the grafted radical moiety in respect to SPI-1. The spatial and temporal control of the process as well as the enhancement of the elastic modulus of the composite are demonstrated and assigned to a higher dispersion of the filler in the polymer matrices as well as to the formation of covalent chemical bonds between the nanoparticles as fillers and the polymer. This work opens the way for preparing new materials for various applications such as membrane, 3D-printing, medicine, photo-and stereo-lithography using various acrylate-based polymer or filler materials (e.g. zeolite, TiO 2 , etc.).

Supporting information

The following data and information are available free of charge via the Internet: list of materials used in this work; experimental part including the methods for characterization; detailed synthesis procedures and conditions; NMR spectra of the organic compounds; grafting procedure c Université de Toulon, Laboratoire MAPIEM, 83041 Toulon, France

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally: Houssein Nasrallah, Rita Zakhia Douaihy.

ACKNOWLEDGMENT

Authors acknowledge the European Union and the Carnot EPS institute for the financial support (3DZeoPol project). Authors acknowledge Dr. Jaafar El Fallah for helping in the SEM analysis.