Cyril Chauveau

Stéphane Fouquay

Guillaume Michaud

Frédéric Simon

Jean-Francois Carpentier
email: jean-francois.carpentier@univ-rennes1

ORCID Sophie M Guillaume
email: sophie.guillaume@univ-rennes1.fr

ORCID Jean-François Carpentier

Polyolefin/Polyether Alternated Copolymers: Silyl-Modified Polymers as Promising Monocomponent Precursors to Adhesives

Keywords:

HAL is

Introduction

Common silyl-modified polymers (SMPs) include polyolefins, polyurethanes (PUs), polyethers or polyacrylates bearing alkoxysilyl functional groups. They are mainly exploited in the coatings, adhesives, sealants and elastomers (CASE) industry. [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF][START_REF] Ebnesajjad | Handbook of Adhesives and Surface Preparation[END_REF][START_REF] Mittal | Handbook of Sealant Technology[END_REF][START_REF] Pizzi | Handbook of Adhesive Technology[END_REF] Indeed, SMPs can harden upon formation of a dense polysiloxane 3D network through the polycondensation of their alkoxysilyl groups with moisture. SMPs also provide an alternative to toxic isocyanateterminated moisture-curable PUs. Furthermore, they are valued for their good adhesion to a wide range of substrates (e.g. glass, plastics and metals), good resistance to temperature and UV irradiation, foaming-free, fast and controlled curing, lack of strong odor or staining, great durability, and reduced health issues. [START_REF] Chruściel | Modification of Thermoplastics with Reactive Silanes and Siloxanes[END_REF][START_REF] Owen | [END_REF][START_REF] Lee | Adhesion Science and Technology[END_REF] The adhesive market is a huge target with almost 14 million tons of adhesives consumed worldwide and a $50 billion turnover for the global adhesive market in 2019. [START_REF] Ceresana | Market Study: Adhesives -World[END_REF] In addition to binding substrates, adhesives provide many other valuable advantages including protection to corrosion, impact and grinding, flexibility between the substrates, lessening of noise and vibrations, reduction of the final weight and cost of the material compared to mechanical binding parts (screws, rivets,..), and insulation of electronic parts. [START_REF] Kinloch | Adhesion and Adhesives Science and Technology[END_REF] Given such a vast market of adhesives which are nowadays part of our daily life, and taking into account that an efficient adhesive is a polymer in a liquid state showing a high chemical affinity with the substrates to bound, and prone to harden into a strong solid upon curing, SMPs are thus both industrially and environmentally attractive since they provide water-based and solvent free monocomponent adhesives. [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF][START_REF] Ebnesajjad | Handbook of Adhesives and Surface Preparation[END_REF][START_REF] Mittal | Handbook of Sealant Technology[END_REF][START_REF] Pizzi | Handbook of Adhesive Technology[END_REF][START_REF] Chruściel | Modification of Thermoplastics with Reactive Silanes and Siloxanes[END_REF][START_REF] Owen | [END_REF][START_REF] Lee | Adhesion Science and Technology[END_REF][START_REF] Ceresana | Market Study: Adhesives -World[END_REF][START_REF] Kinloch | Adhesion and Adhesives Science and Technology[END_REF] Polyolefin-based SMPs (SMPOs) are valuable for their ability to adhere to non-polar and non-porous olefinic surfaces. SMPOs have been traditionally prepared from chemical modification (either in situ functionalization or post-polymerization functionalization) routes, or more valuably from olefin metathesis (self-metathesis, cross metathesis (CM), ringopening metathesis polymerization (ROMP) and acyclic diene metathesis (ADMET)

A c c e p t e d M a n u s c r i p t polymerization) approaches. In particular, the tandem ROMP/CM of a cyclic olefin, in the presence of a symmetric di(alkoxysilyl) functional alkene chain transfer agent (CTA), appears as a valuable, mild and rather highly selective route to SMPOs. [START_REF] Guillaume | Advances in the synthesis of silyl-modified polymers (SMPs)[END_REF] The functional olefinic CTA undergoes CM reactions with the internal C=C bonds throughout the growing polyolefin chains or with the active catalyst moiety bearing the functional group, thus advantageously giving a,ω-chain-end difunctional polyolefins. [START_REF] Chung | Synthesis of telechelic 1,4-polybutadiene by metathesis reactions and borane monomers[END_REF][START_REF] Hillmyer | Preparation of hydroxytelechelic poly(butadiene) via ringopening metathesis polymerization employing a well-defined metathesis catalyst[END_REF][START_REF] Hillmyer | Chain Transfer in the Ring-Opening Metathesis Polymerization of Cyclooctadiene Using Discrete Metal Alkylidenes[END_REF][START_REF] Pitet | Carboxy-Telechelic Polyolefins by ROMP Using Maleic Acid as a Chain Transfer Agent[END_REF][START_REF] Bielawski | Synthesis of End-Functionalized Poly(norbornene)s via Ring-Opening Metathesis Polymerization[END_REF][START_REF] Morita | A Ring-Opening Metathesis Polymerization (ROMP) Approach to Carboxyl-and Amino-Terminated Telechelic Poly(butadiene)s[END_REF] In this regard, we have recently reported a range of SMPOs based on different cyclic olefins prepared by ROMP/CM, catalyzed by some ruthenium complexes in the presence of several bis(trialkoxysilyl)alkene CTAs. [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF] Also, Wagener and co-workers previously reported the preparation by ADMET polymerization of bis(dimethoxymethylsilyl) telechelic polyether/carbosiloxane copolymers, which displayed enhanced elasticity and adhesion properties thanks to the incorporation of some oligo(oxyethylene) segments within the polyolefin. [START_REF] Yuan | Molecular design for silane-terminated polyurethane applied to moisture-curable pressure-sensitive adhesive[END_REF][START_REF] Matloka | Chain Internal/Chain End Latent Crosslinking in Thermoset Polymer Systems[END_REF][START_REF] Matloka | Synthesis and Characterization of Oligo(Oxyethylene)/Carbosilane Copolymers for Thermoset Elastomers via ADMET[END_REF][START_REF] Jiang | Alkoxysilane Functionalized Polyurethane/Polysiloxane Copolymers: Synthesis and the Effect of End-Capping Agent[END_REF][START_REF] Matloka | Chain-End and Chain-Internal Crosslinking in Latent Reactive Silicon Elastomers[END_REF] With the objective to expand the thermo-mechanical and adhesion properties of our SMPOs, we thus tackled the incorporation of "soft" polyether segments within a "rigid" polyolefin backbone. [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] Alternated copolyolefins have been reported by ROMP by several research groups. [START_REF] Ilker | Alternating Copolymerizations of Polar and Nonpolar Cyclic Olefins by Ring-Opening Metathesis Polymerization[END_REF][START_REF] Amir-Ebrahimi | Remarkable alternating effect in metathesis copolymerization of norbornene and cyclopentene using modified Grubbs ruthenium initiators[END_REF][START_REF] Bornand | Mechanism-Based Design of a ROMP Catalyst for Sequence-Selective CopolymerizationAngew[END_REF][START_REF] Lichtenheldt | Alternating Ring-Opening Metathesis Copolymerization by Grubbs-Type Initiators with Unsymmetrical N-Heterocyclic Carbenes[END_REF][START_REF] Vehlow | Alternating Ring-Opening Metathesis Copolymerization of Norborn-2-ene with cis -Cyclooctene and Cyclopentene[END_REF] However, the design of specific asymmetric catalysts was then required in order to achieve such an alternated topology. [START_REF] Bornand | Mechanistically Designed Dual-Site Catalysts for the Alternating ROMP of Norbornene and Cyclooctene[END_REF] Additionally, Grubbs, Choi and co-workers reported the first synthesis of alternated olefin-based copolymers through an original metathesis approach, namely the ring-opening insertion metathesis polymerization (ROIMP) of cyclic olefins and diacrylates (Scheme S1). [START_REF] Choi | Synthesis of A,B-Alternating Copolymers by Ring-Opening-Insertion-Metathesis Polymerization[END_REF][START_REF] Lee | Multiple Olefin Metathesis Polymerization That Combines All Three Olefin Metathesis Transformations: Ring-Opening, Ring-Closing, and Cross Metathesis[END_REF] It was then demonstrated that the fast ROMP of the cyclic olefin first occurs, followed by the slow and progressive insertion of the diacrylate segment within the polymer chains. The ROIMP is thermodynamically driven by the selective bond formation between the cycloalkene and the diacrylate (Table S1). Since the self-metathesis of two electron-deficient acrylate functions is highly unfavorable, [START_REF] Sinclair | Olefin cross metathesis and ringclosing metathesis in polymer chemistry[END_REF] the selective bond formation between the diacrylate and the olefin takes place. Provided a A c c e p t e d M a n u s c r i p t stoichiometric loading in monomers is used, this ensures the formation of highly alternated polymers. Cyclopentene, cycloheptene, cyclododecene, cyclooctene (COE), and COE derivatives were thus copolymerized with alkyl, aryl or diethylene glycol diacrylates. High conversions were obtained for their copolymerization with typical 7-and 8-membered cycloolefins and cyclododecene, with up to 98.5% alternation, high molar mass and moderate dispersity values (Table S1). [START_REF] Choi | Synthesis of A,B-Alternating Copolymers by Ring-Opening-Insertion-Metathesis Polymerization[END_REF] The newly established ROIMP route thus revealed particularly interesting for its tolerance to virtually any diacrylate (macro)molecules, thereby paving the way to the incorporation of functional groups (i.e. ether or aromatic segments) within polyolefins (Table S1, entries 6,7). The ADMET variant of the ROIMP, sometimes referred to as the alternating diene metathesis polycondensation (ALTMET, Scheme S2), was also described along with an example of tandem ROMP/ADMET. [START_REF] Demel | Alternating Diene Metathesis Polycondensation (ALTMET) -A Versatile Tool for the Preparation of Perfectly Alternating AB Copolymers[END_REF][START_REF] Schulz | Solvent Effects in Alternating ADMET Polymerization[END_REF][START_REF] Abbas | Alternating Diene Metathesis Polycondensation (ALTMET) -Opitimizing Catalyst Loading[END_REF][START_REF] Gorodetskaya | Hyperbranched Macromolecules via Olefin Metathesis[END_REF][START_REF] Ding | Efficient Synthesis of Long-Chain Highly Branched Polymers via One-Pot Tandem Ring-Opening Metathesis Polymerization and Acyclic Diene Metathesis Polymerization[END_REF] However, regardless of the improvements achieved during the optimization of this latter approach, the operating conditions (especially the catalyst loading and the reaction temperature) were not suitable for a metathesis polymerization. Noteworthy, to the best of our knowledge, the innovative ROIMP reaction has not been further explored, and there is not precedent of ROIMP or ALTMET performed in the presence of a CTA towards the synthesis of telechelic polyolefins.

We thus report herein on the incorporation of polyether segments within a PCOE backbone, through the ROIMP/CM strategy using commercially available diacrylate endcapped poly(propyleneglycol). Our initial report described the synthesis of a,ω-[Si(OEt) 3 ] 2 -PCOE/PPG* by a one-pot, one-step tandem ROIMP/CM of COE and PPG* with CTA Et catalyzed by G2 in a concentrated reaction medium, along with the thermomechanical and adhesives properties of (cured) SMP copolymers. [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] The present investigations further explore different routes and operating conditions to optimize the synthetic pathway, especially in terms of conversion in each reagent and suitability to access significant amounts of copolymers (Schemes 1, S3-S5). Studies are first based on the simpler tri(propyleneglycol) Comparison of these characteristics, to those of alike siloxane cross-linked PCOE/PPG* materials obtained from the one-step Method I as previously reported, [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] and benchmarking with the commercial adhesive Polyvest E100, reveal improved thermal, mechanical and especially, adhesives features of the new SMPs established in the present work from the twostep ROIMP/CM Method II.

Experimental Section

Materials.

All catalytic experiments were performed under inert atmosphere (argon, < 3 ppm O 2 ) using standard Schlenk line and glove box techniques. Grubbs' 2 nd generation catalyst, ([(IMesH 2 )(Cy 3 P)RuCl 2 (=CHPh)], G2, Aldrich) was used as received. Cyclooctene (COE) was purchased from ACROS, and dried and distilled over CaH 2 before use. Bis(acrylate)tripropyleneglycol referred to as PPG, was kindly provided by Sartomer, and purified by flash chromatography over silica (CH 2 Cl 2 ) and stored over 3Å molecular sieves prior to use (Figure S1). The diacrylate end-capped poly(propyleneglycol 31 diurethane) (PPG[C 6 H 3 (Me)(NHC(O)) 2 ] diacrylate, PPG*; Figure S2; the SEC trace shows three main A c c e p t e d M a n u s c r i p t peaks at M n,SEC = 3500 (59%), 7200 (24%), 12 000 g.mol -1 (13%) with Ð M = 1.0 for each of them, corresponding to three distinct values of repeating units within PPG*, namely n = 1, 2 and 3, respectively), and Polyvest E100 (Evonik, M n,SEC = 5700 g.mol -1 ) were kindly supplied by Bostik and used as received (Figure S3). (E)-But-2-ene-1,4-diyl bis((3-(triethoxysilyl)propyl)carbamate) (CTA Et ) was synthesized as previously described. [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF][START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] Instrumentation and measurements.

1 H (500, 400 MHz) and [START_REF] Hillmyer | Chain Transfer in the Ring-Opening Metathesis Polymerization of Cyclooctadiene Using Discrete Metal Alkylidenes[END_REF] C{ 1 H} (125, 100 MHz) NMR spectra were recorded on Bruker Avance AM 500 and AM 400 spectrometers at 23 °C in CDCl 3 . Chemical shifts (δ) are reported in ppm and were referenced internally relative to tetramethylsilane (δ 0 ppm) using the residual 1 H and [START_REF] Hillmyer | Chain Transfer in the Ring-Opening Metathesis Polymerization of Cyclooctadiene Using Discrete Metal Alkylidenes[END_REF] C solvent resonances of the deuterated solvent.

Monomer conversions were determined from 1 H NMR spectra of the crude polymer sample, from the integration (Int.) ratio Int. Polymer. /[Int. Polymer + Int. monomer ], using the methine hydrogens (-CH=CH-: δ 5.30, 5.66 ppm (PCOE, COE)). Quantitative COE conversion was thus established by 1 H NMR analysis. The typical 1 H and [START_REF] Hillmyer | Chain Transfer in the Ring-Opening Metathesis Polymerization of Cyclooctadiene Using Discrete Metal Alkylidenes[END_REF] C NMR spectra of the final copolymers evidenced the presence of four different chain-ends (i.e. functional groups (FG), Scheme 1), namely trialkoxysilyl chain-ends originating from the CTA (H a-i ), acrylate (Acryl., H l,m ) and vinyl (Vinyl, H j,k ) chain-ends arising from the reaction of PPG ( * ) with COE units, and isomerized (Isom., H n-p ) chain-ends issued from the internal isomerization of vinyl groups (Figure 1). Quantitative analyses of the [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF] 1;

Schemes S6,S7,S8). [START_REF]i.e. the amount of ethylene formed = 100%), and the sum of the amount of non-functional chain-end groups in the polymer plus the amount of isomerized chain-end groups (since no benzoquinone was used to prevent isomerization[END_REF] Experimental molar mass values could not be reliably estimated from NMR spectra due to the latter's complexity and especially because of the overlap of several characteristic signals.

The average molar mass (M n,SEC ) and dispersity (Ð M = M w /M n ) values of the freshly prepared polymer samples (at most within one week following their synthesis unless otherwise stated; stored under argon following synthesis and analyses) were determined by size exclusion chromatography (SEC) in THF at 30 °C (flow rate = 1.0 mL.min -1 ) on a

Polymer Laboratories PL50 apparatus equipped with a refractive index detector and a set of two ResiPore PLgel 3 µm MIXED-E 300 × 7.5 mm columns. The polymer samples were dissolved in THF (2 mg.mL -1 ). All elution curves were calibrated with twelve monodisperse polystyrene standards (M n range = 580-380,000 g.mol -1 ). M n,SEC values of polymers were uncorrected for their possible difference in hydrodynamic volume in THF vs polystyrene. The SEC traces of the copolymers all exhibited a monomodal and symmetric peak.

FTIR spectra of the polymers were acquired (16 scans) with a resolution of 4 cm -1 on a Shimadzu IRAffinity-1 equipped with an ATR module.

Thermogravimetric analyses (TGA) were performed on a Mettler Toledo TGA/DSC1 by heating polymer samples at a rate of 10 °C.min -1 from +25 °C to +500 °C in a dynamic nitrogen atmosphere (flow rate = 50 mL.min -1 ).

A c c e p t e d M a n u s c r i p t

Differential scanning calorimetry (DSC) analyses were performed with a Setaram DSC 131 apparatus calibrated with indium, at a rate of 10 °C min -1 , under a continuous flow of helium (25 mL.min -1 ), using aluminum capsules. The thermograms were recorded according to the following cycles: -100 to 150 °C at 10 °C min -1 ; 150 to -100 °C at 10 °C min -1 .

The apparent viscosity of the SMPs was measured with an ARES G2 planar viscosimeter equipped with a plate-plate geometry, at a speed gradient of 0.01 s -1 over a shear rate range from 0.01 to 100.s -1 . At each imposed shear rate, the apparent viscosity was determined in the steady state regime. The operating temperature was fixed at 30 or 60 ± 0.3 °C. For each sample, the viscosimetric test duration was 5 min. The polymer sample was introduced in between two flat plates inside an oven. A motor was spinning the superior plate, which was in turn spinning the polymer sample. Shear rate (γ, with γ = v/h, v the velocity of the plate (m.s -1 ), h the distance between the two plates (m)) was gradually increased from γ = 0.01 to 500 s -1 . During the measurement, h was kept constant at 0.5 mm. The viscosity of the sample in function of γ was then calculated from the formula:

𝜂𝜂 = 𝐹𝐹 𝛾𝛾 × 𝐴𝐴 (Pa. s)
with F = the force applied to the upper plate by the polymer in response to the movement of rotation (N), and A = the contact area between the sample and the plate (m 2 ). Noteworthy, rheofluidifying polymers are particularly adapted to adhesive applications. They can be easily formulated with catalyst and other additives, they remain homogenous for long periods of time, and their application on surfaces is easy.

Dynamic mechanical analysis (DMA) were performed on a MCR302 Rheometer (Anton Paar) equipped with a CTD450 furnace. An extensional tool was used to make DMA tensile tests. The films were then clamped between the two parallel rolls. The analyzed A c c e p t e d M a n u s c r i p t sample length was 20 mm. To avoid sample slipping during measurements, rough rolls were used. Adhesive films were cut in small rectangular pieces (ca. 30 x 8.5 m; thickness ca. 150 μm). Films were heated from -90 to +150 °C at 2 ° min -1 under nitrogen flow. Linear domains were first measured for each sample on the whole temperature range. Then, the method parameters were adjusted if samples were different from one another. Most of the time, oscillation parameters were fixed at 1 Hz, with a strain amplitude evolving from 0.1 to 0.3 %, between -90 and +150 °C.

CM of PPG ( * ) with several bis(trialkoxysilyl)alkene CTAs using various catalytic systems. Refer to Supporting Information for details (Scheme S3, Tables S2-S3, Figures S4-S13).

One-pot or two-pot, two-step ROMP/CM of COE catalyzed by G2 in the presence of

CTA Et and IM of PPG. Refer to the Supporting information for details (Scheme S4, Tables S4-S5).

One-pot, one-step ROIMP/CM of COE and PPG catalyzed by G2 in the presence of CTA Et . Refer to the Supporting information for details (Scheme S5, Table S6, Figure S14).

One-pot, two-step ROIMP of COE and PPG catalyzed by G2 and CM in the presence of

CTA Et -Method II. The ROIMP of COE and PPG catalyzed by G2 was performed as previously reported with PPG*, yet in the absence of a CTA, in CH 2 Cl 2 at 40 °C during 24 h

(Scheme 1, Table 1). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] The subsequent CM in the presence of CTA Et was next performed in situ (one-pot) upon addition of CTA Et to the reaction mixture at 40 °C during 24 h, as for a classical CM reaction (Scheme 1, Table 2). [START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF] The reaction times were not optimized. Refer to the Supporting information for details. Note that the amount of cyclic polymers could not be determined following the procedure previously reported. [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF] Indeed, the recovered a,ω-[Si(OEt) 3 ] 2 PCOE/PPG copolymers were too reactive to be successfully trapped onto acidified silica during their elution aimed to provide only cyclic copolymers. PPG* catalyzed by G2 followed by the CM with CTA Et was performed in situ (one-pot) as just described above for PPG (Scheme 1), with the following scale-up modifications. Ten individual batches of 10 g each were prepared so as to avoid scaling-up issues inherent to the preparation of 100 g at once. Thus, two-third of the required amount of G2 were sequentially introduced in four portions separated by 1 h in the ROIMP step 1, and the last 1/3rd was then introduced at once during the CM step 2. The 10 batches were next mixed together, and CH 2 Cl 2 was then distilled out under vacuum raising the temperature from 40 °C to 70 °C to ultimately give a brownish highly viscous liquid (Table S7, entries 1-3; each entry thus corresponds to ca. 100 g of copolymer sample recovered from 10 individual two-step

ROIMP/CM experiments) (Figures S15-S27).
One-pot, one-step ROIMP/CM of COE and PPG* catalyzed by G2 in the presence of CTA Et : Large-scale synthesis -Method I. All polymerizations were performed according to the previously reported typical procedure (Table S7, entry 4-6). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] Refer to the Supporting information for details.

All (co)polymers were recovered without purification as a brownish viscous liquid readily soluble in CHCl 3 and THF at 25 °C. All (co)polymer samples were stored under inert atmosphere at room temperature to avoid undesirable polycondensation of their alkoxysilyl groups with surrounding moisture, and analyzed rapidly following their preparation. The obtain the films: 1) SMPs were put in an aluminum cup that was placed on a heating plate.

When the sample was too viscous, the temperature was raised until complete softening of the polymer (ca. 30-65 °C). Then, the catalytic system (1wt% Neostan (S1) + 1wt% aminosilane promoter Geniosil (GF9) (Figure S28) was added and the mixture was manually stirred vigorously with a wooden spatula (thus being exposed to ambient moisture); 2) the mixture was then quickly poured on a silicone or polyethylene terephthalate (PET) foil (preheated when needed) and shaped into a 250 µm thin film by a film applicator; 3) the film was cured under controlled atmosphere (44% moisture, 25 °C) for 7 days (Figures S29-S31).

Tensile tests on the above-prepared tensile pieces. The thickness of the above-prepared tensile pieces was first measured to ensure their homogeneity; suitable values of 0.12-0.15 µm were thus obtained. A tensile piece was then placed in between two jaws, and the jaws then pulled the tensile piece (at a rate of 100 mm.min -1 ) until its rupture. The strain applied as well as the elongation of the material at the rupture point were measured to give an indication of its strength and elasticity, respectively. Satisfactory standard deviations of 0.2 MPa for the strain-at-break, and 6-10% for the elongation at break were then obtained. [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF][START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] affording SMPOs with remarkable selectivities (typically less than 25wt% of cyclic nonfunctional poly(cyclooctene) (PCOE) side-product) and productivities (turnover number (TON) up to 95 000 mol COE .mol Ru -1 and 5 000 mol CTAEt .mol Ru -1 ). [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF] Besides, CTA Et is straightforwardly prepared by the addition of 2-butene-1,4-diol to 3-(triethoxysilyl)propyl isocyanate in bulk conditions. [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF] Also, CTA Et featuring acrylate functions cannot react with the alike PPG ( * ) 's acrylate functions, [START_REF] Sinclair | Olefin cross metathesis and ringclosing metathesis in polymer chemistry[END_REF] thus implying that it can only be bound to a PCOE moiety, thereby driving the selectivity of the process and simplifying the characterization of the resulting polymers. The first screening experiments were performed using PPG, the one prepolymer providing simpler-to-analyze NMR spectra. Subsequent studies focused on the polyether diurethane PPG* segment, which is more valuable thanks to it readily availability and to its intrinsic urethane and aromatic moieties that may improve the properties of the ultimate materials.

Results and discussion

Synthesis and characterization of PCOE/PPG

The very first set of initial experiments, addressing either i) the CM of PPG or PPG* with several bis(trialkoxysilyl)alkene CTAs using various catalysts, or ii) the stepwise metathesis insertion of PPG into the already reported a,ω-bis(triethoxysilyl) PCOE (a,ω-[Si(OEt) 3 ] 2 -PCOE) [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF][START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] in a ROMP/CM/IM approach, or iii) the ROIMP/CM of COE and PPG catalyzed by G2 in the presence of CTA Et , all somehow featuring some limitation, are reported in the Supporting Information (Tables S2-S6; Schemes S3-S5; Figures S4-S14).

Ultimately, polyolefin/polyether PPG*-based SMPs were successfully and effectively prepared by the one-pot, two-step ROIMP/CM strategy on a larger scale (Scheme 1, Method II), for the subsequent evaluation of their (post-curing) thermo-mechanical, rheological and adhesive properties, as described thereafter. 1), [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF] followed by the CM upon addition of CTA Et (24 h; Table 2), successfully afforded the desired telechelic a,ω-bis(triethoxysilyl) PCOE/PPG alternated copolymers (Scheme 1).

Synthesis of PCOE/PPG based SMPs by the one-pot, two-step ROIMP of COE and PPG and subsequent CM with CTA Et

A c c e p t e d M a n u s c r i p t

In the ROIMP first step, regardless of the addition mode of G2 catalyst (all at once or stepwise), a quasi-quantitative conversion of PPG's acrylate end-groups was reached. The high amount of ethylene released during the reaction (Scheme S7) [START_REF]i.e. the amount of ethylene formed = 100%), and the sum of the amount of non-functional chain-end groups in the polymer plus the amount of isomerized chain-end groups (since no benzoquinone was used to prevent isomerization[END_REF] testified of the efficiency of the metathesis reactions, namely the ROIMP of COE/PPG and the CM between the C=C double bonds along the backbone and the acrylate moieties. The reaction was also highly effective, yet only when the catalyst was added stepwise in several aliquots, thus highlighting the importance to repeatedly introduce the catalyst by small portions over the course of the reaction rather than all at once. Under these operating conditions, the reproducibility was then excellent both in terms of acrylate conversion (99%) and ethylene released (89-94%) [START_REF]i.e. the amount of ethylene formed = 100%), and the sum of the amount of non-functional chain-end groups in the polymer plus the amount of isomerized chain-end groups (since no benzoquinone was used to prevent isomerization[END_REF] (Table 1, entries 2-4; Scheme 1). On the other hand, isomerization of the terminal C=C double bond significantly increased with repeated additions and with larger contents of the catalyst (Vinyl/Isom. = 0.05 vs 11.3; Table 1, entry 1 vs entry 2). The difference observed between the molar mass values calculated (M n,theo ) and measured experimentally by SEC (M n,SEC ) most likely originates from the distinct hydrodynamic radii of PCOE/PPG copolymers and of polystyrene standards used for the calibration, and/or from the presence of cyclic polymers formed by ring-closing metathesis upon the release of ethylene. [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | Simple Access to Alkoxysilyl Telechelic Polyolefins from Ruthenium-Catalyzed Cross-Metathesis Depolymerization of Polydienes[END_REF][START_REF] Michel | Tuning the Properties of α,ω-Bis(Trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP)[END_REF][START_REF]i.e. the amount of ethylene formed = 100%), and the sum of the amount of non-functional chain-end groups in the polymer plus the amount of isomerized chain-end groups (since no benzoquinone was used to prevent isomerization[END_REF]42,[START_REF] Vanbiervliet | ω-Epoxide, oxetane and dithiocarbonate telechelic copolyolefins: access by ring-opening metathesis/cross-metathesis polymerization (ROMP/CM) of cycloolefins in the presence of functional symmetric chain-transfer agents[END_REF][START_REF] Vanbiervliet | From Epoxide to Cyclodithiocarbonate Telechelic Polycyclooctene through Chain-Transfer Ring-Opening Metathesis Polymerization (ROMP): Precursors to Non-Isocyanate Polyurethanes (NIPUs)[END_REF] NMR analyses ( 1 H, J-MOD, COSY, HSQC, HMBC; Figures S15-S18) of an aliquot of the crude ROIMP reaction mixture confirmed the presence of COE units (H A-D , C A-D ), COE-PPG segments (H E-I , C E-I,M ), along with residual acrylate ( H c,d ,C c,d ),vinyl (H a,b ,C a,b ) and C=C isomerized (issued from the isomerization of vinyl groups; H e-g , C e-g ) chain-end groups (Schemes 1,S6).

Correspondingly, ESI-MS analysis of this same sample revealed the presence of linear non(alkoxysilyl) functional chains (i.e. terminated by a vinyl, an acrylate or an isomerized vinyl group; Figure S19, population in blue), and of cyclic nonfunctional chains (Figure S19, population in red) of alternated PCOE/PPG copolymers. These populations were also A c c e p t e d M a n u s c r i p t observed with a missing or an additional CH 2 in the ring opened octene chain, evidencing the internal isomerization processes (Scheme S8). [START_REF] Diallo | α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF][START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF] (%)

Released ethylene [c] (%)

Polymer chain-end ratio [d] M n,theo

[e]
(g.mol -1 )

M n,SEC [f] (g.mol -1 ) Ð M [f]
Acryl. Vinyl Isom. [a] [COE] 0 /[PPG] 0 = 1500:500, [COE] 0 +[PPG] 0 = 0.5 M, reaction performed with under a flow of argon to remove the ethylene formed; reaction times were not optimized; 100 % conversion in COE as determined by [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF] H NMR analysis (refer to the Experimental Section). [b] Conversion in PPG's acrylate functions as determined by 1 H NMR monitoring. [c] Determined by 1 H NMR spectroscopy; note that the amount of ethylene is underestimated. 41 [d] Ratio of acrylate (Acryl.), vinyl (Vinyl) and C=C isomerized (Isom.) chain end-groups as determined by [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF] H NMR spectroscopy (refer to the Supporting Information; Scheme S6). [e] Theoretical molar mass calculated from the formula: Once complete conversion of the acrylate achieved, the second CM step was performed in situ (one-pot) upon the simultaneous addition to the reaction mixture of G2 and CTA Et (Scheme 1). A single addition of two equiv of G2 revealed better than a stepwise addition in terms of CTA Et conversion (86-97% vs ca. 75%, Table 2, entries 1-4, 6 vs 5). The amount of ethylene released [START_REF]i.e. the amount of ethylene formed = 100%), and the sum of the amount of non-functional chain-end groups in the polymer plus the amount of isomerized chain-end groups (since no benzoquinone was used to prevent isomerization[END_REF] did not vary much from the ROIMP-step 1 to the CM-step 2, with a maximum increase of ca. 4% (within the uncertainty of the NMR measurements; Table 2).; this is most likely because most of the vinyl chains were consumed in the first ROIMP step and only a few isomerized, nonreactive ones remained. Under optimized conditions, a ratio of up to 66-73% of terminal ethoxysilyl end-functions was obtained, thus showing a fairly efficient CM reaction ( [START_REF] Choi | Synthesis of A,B-Alternating Copolymers by Ring-Opening-Insertion-Metathesis Polymerization[END_REF] These results highlight that the ROIMP of COE and PPG first step is decisive: if high conversions in both acrylate and eventually released ethylene are reached, the targeted telechelic copolymer is likely to be formed from the following CM step, with a high molar mass and a high content of alkoxysilyl chain-end groups. In this regards, sequential addition of G2 in the first ROIMP step is thus compulsory (yet, at the expense of increasing isomerization), whereas the catalyst should be introduced at once in the last CM step. Entry PCOE/PPG (Table 1)

M n,theo = {([COE] 0 × conv. COE × M COE ) + ([PPG] 0 × conv. PPG × M PPG )} / {[PPG] 0 × conv. PPG × (1 -released ethylene)} (
[G2] 0 (mol equiv)

[CTA Et ] 0 [b] (mol equiv) Conv. CTAEt [b] (%)
Released ethylene [b] (%)

Polymer chain-end ratio [b] M n,theo

[c] (g.mol -1 ) M n,SEC [d] (g.mol -1 ) Ð M [d]
Acryl. Si(OEt) 3 Vinyl Isom. [a] Reaction performed under a flow of argon to remove the ethylene formed; [COE] 0 +[PPG] 0 = 0.5 M, [G2] 0 = 0.2 mol%; 100 % conversion in COE as determined by [START_REF] Da Silva | Handbook of Adhesion Technology[END_REF] H NMR analysis (refer to the Experimental Section). [b] Determined by 1 H NMR spectroscopy (refer to the Experimental Section). [c] Calculated from the formula:

M n,theo = ([COE] 0 × conv. COE × M COE + [PPG] 0 × conv. PPG × M PPG + [CTA Et ] 0 × conv. CTAEt × M CTAEt ) / ([PPG] 0 × conv. PPG × (1 -release ethylene ) + [CTA Et ] 0 × conv. CTAEt )
, with M COE = 110 g.mol -1 , M PPG = 300 g.mol -1 and M CTAEt = 582 g.mol -1 . [d] Number-average molar mass (M n,SEC ) and dispersity (Ð M = M w /M n ) values determined by SEC vs polystyrene standards in THF at 30 °C.

A c c e p t e d M a n u s c r i p t

Thermal, rheological, mechanical and adhesive properties of (cured) a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs.

Thermal and rheological properties of a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs before curing.

The thermal and rheological properties of PCOE/PPG* SMPs, referred to as PCOE x /PPG* y -CTA Etz copolymers (with x, y, z = weight fraction of PCOE, PPG*, and CTA Et and x + y + z = 100 wt%; M n,SEC ca. 13 000 g mol -1 , Ð M ca 2.3), prepared from the two-step ROIMP/CM approach -large-scale synthesis Method II (ca. 100 g; refer to the Experimental Section; Scheme 1), have been studied before curing. They were then compared to the alike previously reported copolymers synthesized from the one-step ROIMP/CM Method I (Scheme S5), as previously characterized [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] (Table S7; Figure S25). A Si(OEt 3 ) 2 weight fraction of z = 0.15 was essentially considered in the present work since our previous investigations showed that a higher trialkoxysilyl content (z = 0.22) disfavored the copolymer thermal stability, while not significantly modifying its thermal transition temperatures (Table 3). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] The SMPs performances were benchmarked against a commercially available triethoxysilylfunctionalized polybutadiene used as adhesives resin (Polyvest E100). Polyvest E100 was selected, among the very few alkoxysilane-terminated polybutadiene available on the commercial market, for its low viscosity, a characteristic required for adhesive applications.

Due to its unsaturated backbone and terminal Si(OEt) 3 functionalities, this apolar and hydrophobic resin is used as a highly reactive binder for its very good dispersing properties of inorganic fillers in various fields of applications (in particular as adhesives and sealants, or as additive for tires, waterproofing membranes and coatings, dispersion additive for rubber based formulations). 45 TGA analyses of PCOE/PPG*-CTA Et15 SMPs (Method II) of similar molar mass (M n,SEC ca. 13 000 g mol -1 , Ð M = 2.5) showed that inclusion of more temperature sensitive 3, entry 2 vs 3-5; Table S8). All the PCOE/PPG*-CTA Et15 copolymers displayed a three-step degradation profile, corresponding to first the polycondensation and degradation of triethoxysilyl functions (ca. 150-250 °C), followed by the degradation of the PPG* segments (ca. 250-350 °C), and then the degradation of PCOE units (ca. 350-450 °C) (Figure S26). The thermal degradation profile of the samples prepared in the present work from the two-step ROIMP/CM Method II (Scheme 1) is the same as the one observed for the alike PCOE/PPG* samples obtained from the similar one-step ROIMP/CM Method I (Scheme S5). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] The copolymers prepared from the two-step tandem ROIMP/CM Method II exhibited a slightly lower stability (∆T d ca. 20-33 °C) than the previously reported samples prepared from the direct route Method I (Table S8); [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] this is possibly due to the presence of residual PPG* oligomers within PCOE [START_REF] Sinclair | Olefin cross metathesis and ringclosing metathesis in polymer chemistry[END_REF] /PPG* 50 -CTA Et15 reported herein that may act as plasticizers (vide supra, Figure S25). DSC analysis of all PCOE x /PPG* y -CTA [START_REF] Bielawski | Synthesis of End-Functionalized Poly(norbornene)s via Ring-Opening Metathesis Polymerization[END_REF] copolymers showed a semi-crystallinity that slightly increases with higher PCOE contents (Table 3, Figure S26). 46 The comparison with a PPG*-free PCOE-CTA Et sample (Table 3, entry 2) [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF] highlights the significant increase in glass transition temperature values for the PCOE/PPG*-CTA Et15 SMPs (∆T g ca. 18 °C), while upon PPG* inclusion, the crystallization (T c ) and the melting (T m ) temperatures were recorded at lower values and the crystallinity decreased drastically (∆H cryst ca. -103 J.g -1 ). Copolymers obtained from the one-step ROIMP/CM Method I that we previously reported [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] generally displayed higher T g and crystallinity than those prepared herein from the two-step Method II; this possibly originates from an earlier polycondensation during the DSC analysis that generates siloxane bridges which improve the thermal stability, as corroborated by TGA measurements.

On the other hand, the benchmarked Polyvest E100 (of yet a lower molar mass) was shown to A c c e p t e d M a n u s c r i p t be amorphous and more thermally stable (T d 10% = 329 °C) than any of the uncured PCOE/PPG*-CTA Et15 SMPs, regardless of their synthetic route (Table 3, Figure S26). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] A c c e p t e d M a n u s c r i p t (°C) [START_REF] Michel | ω-Bis(Trialkoxysilyl) Difunctionalized Polycyclooctenes from Ruthenium-Catalyzed Chain-Transfer Ring-Opening Metathesis Polymerization[END_REF] a,ω-[Si(OEt) [a] Degradation temperatures determined by TGA with T d x = temperature at which x% of mass loss occurs (refer to Supporting Information). [b] Glass transition (T g ), crystallization (T c ) and melting (T m ) temperatures, and crystallization enthalpy (∆H cryst ) determined by DSC (refer to the Supporting Information). [c] M n,SEC = 5700 g.mol -1 , refer to the Experimental Section. n.d. not determined; n.o. not observed.

T d 20% [a] (°C) T d 10% [a] (°C) T d 20% [a] (°C) T g [b] (°C) T c [b] (°C) T m [b] (°C) ∆H cryst [b] (J.g -1 ) T g [b] (°C) T c [b] (°C) T m [b] (°C) ∆H cryst [b] (J.g -1 ) 1 PPG* 294 317 - - -45 - - - - - - - 2

A c c e p t e d M a n u s c r i p t

The viscosities of α,ω-[Si(OEt) 3 ] 2 -PCOE/PPG* prepared herein from the two-step ROIMP/CM Method II feature a rheofluidifying behavior below their T m (i.e. at 30 °C). A quite high viscosity at low share rate (η γ=0.1 = 3000-11 000 Pa.s) and a low viscosity at high share rate (η γ=100 = 21-270 Pa.s) were recorded, while the viscosity generally increases with higher molar mass copolymers. Above their T m (i.e. at 60 °C), the copolymers then display a Newtonian behavior along with a lower viscosity (η γ=0.1 = 4-12 Pa.s, η γ=100 = 3-8) (Table 4;

Figure 2). A similar rheological behavior was observed with the alike previously reported copolymers prepared from the direct one-step approach Method I (Table S9); [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] on the other hand, Polyvest E100 displays a Newtonian behavior at 30 °C (Table 4; Figure 2). All these SMPs combine a rather high thermal stability and low crystallinity, with a very low viscosity either under stress or temperature, thereby foreseeing easy processing and hinting at promising industrial outcomes. a,ω-[Si(OEt) 3 ] 2 -PCOE n.d. [b] n.d. [b] n.d. [b] n.d. [b] n.d. [b] n.d. [a] Viscosity and rheological behavior as determined by viscosimetry using a Contraves Low Shear 30 viscosimeter; uncertainty = ±5% (refer to Supporting Information). [b] n.d. Not determined because the polymer is solid.

A c c e p t e d M a n u s c r i p t 4, S10). The last two data points depicted in the curves have most likely been impacted by the mass loss occurring during the rotation at high shearing and should thus not be taken into account.

Thermo-mechanical properties of a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs after curing.

The a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* copolymers synthesized from the two-step ROIMP/CMlarge-scale synthesis Method II, were then cured using the previously successfully investigated catalytic system composed of the organotin(IV) catalyst Neostan (S1, 1wt%) and aminosilane promoter Geniosil (GF9, 1wt%), and surrounding moisture (Figure S28). [START_REF] Pizzi | Handbook of Adhesive Technology[END_REF][START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF]47,48 Homogenous and solid films obtained from the cured PCOE/PPG* SMPs samples, then provided tensile pieces suitable for thermo-mechanical investigations (Figures S29-S31).

Note that following this same procedure, cross-linked (COE-free) a,ω-[Si(OEt) 3 ] 2 -PPG* A c c e p t e d M a n u s c r i p t generated a film that was too fragile to afford cohesive-enough tensile pieces. Also, the previously reported a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* copolymers prepared from the direct/one-step ROIMP/CM Method I, [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] turned out to be too hard to be stretched into an homogeneous film; this prevented the elaboration of suitable tensile pieces and precluded comparison of their thermomechanical properties to those of the copolymers herein investigated.

As expected, the formation of a siloxane network upon curing clearly increased the thermal stability of the SMPs, as revealed by TGA analysis (Table 3; following curing: ∆T d 10% ca. +33, ∆T d 20% ca. +44 °C). In particular, the thermograms evidenced the disappearance of the first degradation step, while the second one remained unchanged (Figure S26). In addition, all thermal transition temperatures, except the melting temperature, significantly decreased upon curing (∆T c = -(2-7) °C; ∆T g = -(13-15) °C; ∆T m = +12 °C). Also, the crosslinked SMPs were more crystalline (Table 3; before curing ∆H cryst ca. -8.5 J.g -1 , after curing, ∆H cryst ca. -13.5 J.g -1 ). These thermal profiles are yet difficult to be further rationalized in light of the complex structure of these materials and given the limited literature reports on the thermal stability of SMPs.

The viscoelastic behavior of the SMP materials reported herein has been investigated by DMA (Figure 3; Table S11). Polyvest E100 film displayed a rather constant modulus and only one rubbery plateau with a relatively high E' modulus. The peak at ca. 100 °C on the tan δ = E"/E' originates from both the increase of the loss modulus (E'') and the drop of the storage modulus (E'). This tan δ peak indicated a high mobility of the polymer in the 3D network, the latter which yet did not enable the material to flow (the two E" and E' curves staying separated, i.e. not crossing each other). For α,ω-[(EtO) 3 Si] 2 -PCOE/PPG* copolymers cured with S1/GF9 (1:1wt%), a first plateau appeared at ca. 25 °C (Figure 3b,d, Table S11)

with the corresponding E' value increasing with the PCOE content (Table S11, entries 2-4);

A c c e p t e d M a n u s c r i p t this highlighted the cohesion and mechanical strength imparted by PCOE units. After the first rubbery plateau, the elastic contribution E' dropped again. This second plateau was indicative of the PCOE melting: the larger the PCOE content, the larger the drop (Table S11, entries 2-4). We assumed that the first plateau was much higher due to the various contributions of entanglements of amorphous parts, of crystalline areas and of cross-linked chains. Thus, when the crystalline moieties merge, part of the rigid network is lost and the E' modulus falls down.

Finally, these PCOE/PPG* cross-linked copolymers do not display the second peak of tan δ observed with Polyvest E100. Instead, E' and E'' remain more constant, representative of a stiffer 3D network. (Table S11).

The average entanglement molecular weight (M e ) within the 3D networks has been estimated through a model based on the elastic deformation using the formula M e (g.mol -1 ) = (ρ × R × T)/E', where ρ is the density of the material, R the ideal gas constant, T the temperature and E' = the storage modulus at this temperature (Table 5). 49 However, since the present SMPs feature distinct segments, calculated M e values will deviate from the initial model and will only be indicative of the 3D network. Also, Polyvest E100 (M e = 300 g.mol -1 ; Table 5, entry 1) cannot reliably be compared to the SMPs due to their molecular differences. Since a larger PCOE content improved the chain flexibility, it induced more entanglements and thus lowered the corresponding M e value, as experimentally observed on the first plateau (Table 5, entries 2-4). M e evolution at the second plateau basically followed the trend observed at the first plateau, except for the PCOE [START_REF] Sinclair | Olefin cross metathesis and ringclosing metathesis in polymer chemistry[END_REF] /PPG* 50 -CTA Et15 cross-linked copolymer for which M e values were lower than expected (Table 5, entries 3). The differences observed between values at the two plateaus may arise from the difficulty to maintain a constant tension on the film after the second transition, due to the softening and relaxing of the film, thereby inducing some imprecision on the measurements.

Adhesion efficiency of cured a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs.

The adhesion efficiency of the S1/GF9(1:1wt%)-cured a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs synthesized by the two-step ROIMP/CM route -large-scale synthesis (Method II) was then evaluated and benchmarked against Polyvest E100 (Figure 4b). All PCOE/PPG* cross-linked SMPs showed good adhesion, with a strain-at-break of 3.4(0.1)-4.0(0.1) MPa, significantly superior to that of Polyvest E100 (strain-at-break value of 2.6(0.1) MPa). We assume that PPG* imparted a better elasticity to the polyolefin segment, in agreement with the abovementioned DMA and tensile data. Surprisingly enough, the PCOE/PPG* ratio did not seem to really impact the adhesive properties. In comparison, the previously reported S1/GF9(1:1wt%)-cured PCOE 50 /PPG* [START_REF] Sinclair | Olefin cross metathesis and ringclosing metathesis in polymer chemistry[END_REF] -CTA Et15 SMPs synthesized by the one-step ROIMP/CM Method I, [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] displayed a twice as low strain-at-break as the alike copolymer prepared in the present work by the two-step route -large-scale synthesis (Method II) (1.7 [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] vs 4.0 MPa, respectively). This most likely originates from the presence, within the present copolymer sample, of larger amounts of plasticizing oligomers (as evidenced by SEC analyses, Figure S25) that provide a higher resistance to strain.

Conclusion

Several original bis(trialkoxy)-functional polyether/polyolefin alternated copolymer materials were synthesized by Ru-catalyzed metathesis reactions following distinct CM, ROIMP/CM, A c c e p t e d M a n u s c r i p t

or ROMP/CM/IM strategies. Among these latter approaches, the herein described one-pot, two-step tandem ROIMP of COE with PPG* and subsequent CM with CTA Et (Method II, Scheme 1) revealed most performant for the large scale preparation of the desired SMPs.

a,ω-[Si(OEt) 3 ] 2 -PCOE/PPG* materials featuring various ether-to-olefins ratios were then prepared (M n,SEC up to 14 000 g.mol -1 ) and characterized molecularly by NMR and SEC investigations. The polyether/polyolefin copolymers showed lower thermal stability and thermal characteristics (T m and T c ) than both a PCOE (PPG*-free homopolymer) or the benchmark polybutadiene Polyvest E100 (Tables 3,S7). Oligomers present alongside the desired copolymers (as evidenced by SEC analyses; Figure S25) acted as plasticizers, enhancing in turn the thermal, mechanical and adhesive properties of the materials, as well as their ease of processability. The alternated copolymer samples were isolated as rheofluidifying solids, i.e. materials that behave as a solid under a weak solicitation, yet as a fluid when a force is applied onto them.

After curing of these SMPs from moisture using the catalyst system S1/GF9, DMA measurements evidenced that PPG* segments enhanced the elasticity of the cross-linked materials as compared to Polyvest E100 (Figure 3). Strains-at-break recorded from tensile tests were generally similar to that of Polyvest E100, while wood adhesion properties revealed superior for the PCOE/PPG* copolymers (Figure 4). Comparison of materials with different PCOE-to-PPG* ratio suggested that the higher the content in PCOE in the cross-linked alternated copolymers, the higher the thermal stability, the crystallinity, and the strength of the SMPs; however, the elasticity and the cross-linking density determined by DMA were then lower (Figure 3; Tables 3,5,S11). These cured PCOE/PPG* SMP materials showed a better resistance to strain than the previously reported alike PCOE/PPG* materials prepared from a direct one-step procedure (Method I). [START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] A c c e p t e d M a n u s c r i p t

The herein exploited ROIMP/CM strategy towards the large-scale preparation of alternated polyether/polyolefin (Method II) successfully provides monocomponent SMPs with promising thermal, mechanical and especially, adhesives characteristics (strain-at-break on wood up to 4.0 MPa) improved as compared to the benchmarked industrial Bostik adhesive Polyvest E100. Envisioned outcomes of these polyether/polyolefin materials are in particular for CASE applications requiring improved resistance to humidity and hydrolysis (as imparted by the polyolefin segments), and for (semi)structural bonding applications in automotive or transport markets. These preliminary results, obtained without optimization nor formulation of the adhesives (i.e. free of any additives, fillers or charges), can likely be further improved to enhance their properties and widen the field of applications, in particular as viable alternative to current polyurethane adhesives. 50

ASSOCIATED CONTENT

A c c e

  p t e d M a n u s c r i p t diacrylate polyether (PPG) model and next complemented with the industrially-relevant poly(propyleneglycol 31 diurethane) diacrylate (PPG*). These various synthetic strategies demonstrate that one-pot approaches based on the tandem ROIMP/CM of COE and PPG* with CTA Et catalyzed by G2 (two-step Method II -herein establishedand one-step Method I -previously reported -26 ) are the most suitable pathways towards the large-scale preparation of such polyolefin/polyether SMP materials. The thermo-mechanical, rheological and adhesive properties of the thus herein synthesized (Method II), and of the subsequently cured corresponding new PCOE/PPG* SMP materials, are next examined to probe in particular the impact of the polyether segments' length and the content of trialkoxysilyl moieties.

A c c e p t e d M a n u s c r i p t

  One-pot, two-step ROIMP of COE and PPG* catalyzed by G2 and CM in the presenceof CTA Et : Large-scale synthesis -Method II. Practically, the ROIMP/CM of COE and

  isolated a,ω-[(EtO) 3 Si] 2 -(PCOE)/PPG ( * ) (co)polymers were characterized by 1 H and 2D NMR and FTIR spectroscopies, and SEC analyses. Preparation of films and tensile pieces from cured PCOE/PPG* SMPs synthesized from the two-step ROIMP/CM approach. The cured SMP materials were first shaped as tensile pieces that were cut out of thin films made from them. The following procedure was used toA c c e p t e d M a n u s c r i p t

Scheme 1 .

 1 Scheme 1. Synthesis of a,ω-[Si(OEt) 3 ] 2 -PCOE/PPG ( * ) by the one-pot, two step ROIMP of COE with PPG ( * ) and CM with CTA Et catalyzed by G2 -Method II, illustrated with PPG, and chemical structure of the poly(propyleneglycol) diacrylates (PPG ( * ) ), bis(triethoxysilyl) diurethane CTA Et , Grubbs' second generation catalyst G2, and of the possible chain-end groups (FG) of the (co)polymers investigated in the present work.

  refer to the Supporting Information), with M COE = 110 g.mol -1 and M PPG = 300 g.mol -1 . [f] Numberaverage molar mass (M n,SEC ) and dispersity (Ð M = M w /M n ) values determined by SEC vs polystyrene standards in THF at 30 °C. n.d. not determined.

NMR ( 1 H

 1 , J-MOD, COSY, HSQC, HMBC) and FT-IR analyses of the recovered telechelic a,ω-bis(triethoxysilyl) PCOE/PPG alternated copolymers (a,ω-[Si(OEt) 3 ] 2 -PCOE/PPG), evidenced the same macromolecular structure as the one observed for PCOE/PPG copolymers obtained from the previous ROIMP step 1 (FiguresS15-S18), along with the additional signals of the ethoxysilyl functional end-groups being clearly identified (H a-i , C a-i,q ) (Figures1,S20-S23). Furthermore, ESI-MS analysis provided another strong support for the formation of the telechelic alternated PCOE/PPG copolymers, including mono-and difunctional, linear non-functional, cyclic non-functional and internally isomerized polymers (FigureS24). Overall, these observations nicely demonstrated the formation of telechelic a,ω-bis(triethoxysilyl) PCOE/PPG alternated copolymers as major products with minor defects. This latter tandem ROIMP/CM one-pot, two-step approach (Method II), along with the former simpler direct one-pot, one-step alike ROIMP/CM route (Method I, Refer to A c c e p t e d M a n u s c r i p t Supporting Information),[START_REF] Chauveau | ω-Bis(trialkoxysilyl) Telechelic Polyolefin/Polyether Copolymers for Adhesive Applications Using Ring-Opening Insertion Metathesis Polymerization Combined with a Chain-Transfer Agent[END_REF] thus provide two suitable synthetic pathways towards the targeted telechelic a,ω-[(EtO) 3 Si] 2 -PCOE/PPG ( * ) alternated copolymers (Schemes 1,S5). These two strategies were then next implemented and optimized for the larger scale preparation of PCOE/PPG* SMPs to evaluate their thermo-mechanical and rheological properties before and after curing, and ultimately their adhesive ability.

A c c e p t e d M a n u s c r i p t

Figure 1 .

 1 Figure 1. 1 H and J-MOD NMR spectra (400 and 100 MHz, 23 °C, CDCl 3 ) of an

A c c e

  p t e d M a n u s c r i p t PPG* segments along the polyolefin, greatly and proportionally alters its thermal stability (T d 10% = 406 vs 258-275 °C; Table

Table 4 .

 4 Rheological characteristics of α,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs synthesized by the one-pot, two-step ROIMP/CM route -large-scale synthesis (Method II) (TableS7, S10).

Figure 2 .

 2 Figure 2. Viscosity as a function of shear rate measured at 30 °C (dots) and 60 °C (squares)

Figure 3 .PCOE 20 /

 320 Figure 3. E', E'' and Tan δ as a function of temperature measured by DMA analysis of

Figure 4 .

 4 Figure 4. a) Strain-at-break (■) and elongation-at-break (■) of S1/GF9(1:1wt%)-cured

( * ) -based SMPs by a ROIMP/CM approach.

	The design of polyolefin/polyether based SMPs by metathesis reactions was focused on the
	tandem ROMP of a common cyclic olefin, COE, and insertion metathesis (IM) of
	commercially	available	polyethers	such	as	tri(propyleneglycol)	or
	poly(propyleneglycol 31 diurethane) diacrylate (PPG ( * ) ), catalyzed by Grubbs' second
	generation catalyst (G2), associated with a CM using the bis(triethoxysilyl) diurethane CTA
	{(EtO)

3

Si(CH 2 ) 3 NHC(O)OCH 2 CH=} 2 (CTA Et ) (Scheme 1). Indeed, G2 typically affords the best compromise in terms of price, commercial availability and efficiency. Also, the A c c e p t e d M a n u s c r i p t diurethane CTA Et was previously shown to be highly effective in metathesis ROIMP reactions,

Table 1 .

 1 ROIMP of COE and PPG catalyzed by G2 performed in CH 2 Cl 2 at 40 °C during 2 h

	(Scheme 1) -Method II.
	Entry	[G2] 0 [a]	Conv. acrylate [b]

Table 2

 2 redistribution of the chains mediated by the CTA during the CM (M n,SEC-ROIMP = 14 000-43 100 g.mol -1 vs M n,SEC-ROIMP/CM = 4400-6000 g.mol -1 ; Table1vs Table2 entries1,2,5). The dispersity values of the copolymers (D M = 1.7-1.8) were typical of a metathesis

	M a n u s c r i p t
	A c c e p t e d

, entries 1-5). As anticipated, M n,SEC values were systematically lower than the ones obtained after the first ROIMP step, due to the

Table 2 ,

 2 entry 6). Signals at δ 1H 1.8 ppm and δ 13C 35, 138 and 145 ppm could not be unambiguously assigned.

Table 2 .

 2 CM of PCOE/PPG catalyzed by G2 in the presence of CTA Et performed in CH 2 Cl 2 at 40 °C during 24 h (Scheme 1) -Method II.[a]

Table 3 .

 3 TGA and DSC thermal characteristics of α,ω-[(EtO) 3 Si] 2 -PCOE/PPG* synthesized by the one-pot, two-step ROIMP/CM route -largescale synthesis (Method II), before and after curing (TableS7).

			Before curing	After curing	Before curing	After curing
	Entry	Polymer	T d 10% [a]

Table 5 .

 5 Calculated Me values of S1/GF9(1:1wt%)-cured a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs synthesized by the one-pot, two-step ROIMP/CM route -large-scale synthesis (Method II).The mechanical properties of the S1/GF9(1:1wt%)-cured a,ω-[(EtO) 3 Si] 2 -PCOE/PPG* SMPs prepared from the two-step ROIMP/CM route -large-scale synthesis (Method II) were evaluated from tensile tests using the tensile pieces cut out from the films (refer to the Experimental Section). PCOE units were shown to provide strength and rigidity to the cross-linked copolymer materials, whereas PPG* units imparted elasticity, thereby confirming DMA data. All PCOE/PPG* SMPs reported herein showed a higher elongation-at-break than Polyvest E100, the benchmark material with a sole polyolefin backbone (Figure4a). The cured PCOE 50 /PPG* 35 -CTA Et15 afforded the best compromise with the highest strain-at-break (3.3 MPa) and a good elongation-at-break (44%), both being superior to those of Polyvest E100 (2.2 MPa and 40%, respectively). This is actually not surprising as PCOE 50 /PPG* 35 -CTAEt15

				M a n u s c r i p t
	Entry A c c e p t e d SMPs ρ (kg.m -3) (°K) T	E' (MPa) rubbery st	2 nd rubbery	M e (g.mol -1 ) rubbery 1 st 2 nd rubbery
					plateau	plateau	plateau	plateau
	1	Polyvest E100	997	298	8.4	-	300	-
	2	PCOE 20 /PPG* 65 -CTA Et15	892	298	3.2	1.6	700	1850
	3	PCOE 35 /PPG* 50 -CTA Et15	1014	298	13.7	8.7	250	3500
	4	PCOE 50 /PPG* 35 -CTA Et15	957	289	32.8	22.0	80	1350

also displayed the lowest M e values (80 and 1350 g.mol -1 ; Table

5

, entry 4), highlighting a denser and stiffer network. These results thus foresee PCOE/PPG-CTA Et copolymers as materials with promising mechanical properties for CASE applications.

ACKNOWLEDGEMENTS

Financial support of this research by Bostik (Ph.D. support to C.C.) is gratefully acknowledged. Dr B. Colin and Dr J. Brand (Bostik) are gratefully acknowledged for their help with the mechanical tests. P. Jehan (CRMPO -UMS Scanmat Rennes) is gratefully acknowledged for MS analyses.

A c c e p t e d M a n u s c r i p t

Supporting Information

The Supporting Information including detailed and complementary experimental section and complementary data on the PCOE/PPG* copolymers, is available free of charge on the ACS Publications website at DOI: XXX/.

AUTHOR INFORMATION

Corresponding Author

*E-mail: jean-francois.carpentier@univ-rennes1.fr; sophie.guillaume@univ-rennes1.fr


Jessye Dos Santos
email: j.dossantos@estia.fr

Guillaume Terrasson
email: g.terrasson@estia.fr

Alvaro Llaria
email: a.llaria@estia.fr

Improving Low Power Listening (LPL) Mechanism to Save Energy Consumption in WSN

As stated in the literature, Low Power Listening (LPL) duty cycle is one of the most common energy conservation solution for WSN. By using channel check mechanism, the purpose of LPL solutions is to reduce the energy consumption of the listening phase. In this paper, we propose to study the performances and limitations of this kind of solutions. Therefore, we deploy a ContikiMAC LPL on both real and simulated WSN platform to demonstrate the impact of LPL on the energy consumptions of the node radio and microcontroller but also on the application Quality of Service. Based on the obtained results, shortcomings of LPL solutions are highlighted and potential improvements are discussed such as the use of multi-parameter dynamic duty cycle.

I. INTRODUCTION

Wireless Sensor Networks (WSN) consist of hundreds or thousands of small devices called nodes. Nodes are in general composed of a microcontroller (MCU), memories and a wireless transceiver (RF) [START_REF] Johnson | A comparative review of wireless sensor network mote technologies[END_REF]. They also embed heterogeneous sensors (temperature, humidity, accelerometers...) to monitor their environments. Thanks to standards as 6LoWPAN [START_REF] Hui | 6lowpan: Incorporating ieee 802.15. 4 into the ip architecture[END_REF], WSN nodes become smart and can be part of Internet of Things (IoT) paradigm.

Therefore, deployed at different areas, these tiny devices allow various applications as smart agriculture [START_REF] Heble | A low power iot network for smart agriculture[END_REF]- [START_REF] Sales | Wireless sensor and actuator system for smart irrigation on the cloud[END_REF], Industry 4.0 [START_REF] Raza | Industrial wireless sensor and actuator networks in industry 4.0: Exploring requirements, protocols, and challenges a mac survey[END_REF]- [START_REF] Watteyne | Industrial wireless ip-based cyber-physical systems[END_REF] or smart campus/smart home [START_REF] Stavropoulos | A smart university platform for building energy monitoring and savings[END_REF]- [START_REF] Butt | Development of smart home automation system by using controlled network[END_REF]. All these applications need robust and reliable technologies for collecting and sending data. Nevertheless, sensor nodes are currently powered with batteries which leads to limit WSN lifetime [START_REF] Karray | A comprehensive survey on wireless sensor node hardware platforms[END_REF]. So, it is essential to propose and develop energy optimization solutions aimed at reducing node energy consumption without downgrading the network Quality of Service (QoS) [START_REF] Babayo | A review on energy management schemes in energy harvesting wireless sensor networks[END_REF].

As exposed in the literature, these solutions can be implemented at hardware or software levels [START_REF] Musaddiq | A survey on resource management in iot operating systems[END_REF]. For example, in [START_REF] Silva | Power-management techniques for wireless sensor networks and similar low-power communication devices based on nonrechargeable batteries[END_REF] and [START_REF] Patil | Fpga based power saving technique for sensor node in wireless sensor network (wsn)[END_REF], the developed nodes embed hardware solutions which manage parameters such as MCU frequency, supply voltage or current of the components in order to save energy. As pointed out in [START_REF] Musaddiq | A survey on resource management in iot operating systems[END_REF], this kind of hardware solutions cost the creation or addition of components and cannot be simply deployed on existing nodes. On the other hand, software solutions, can be deployed on each OSI layers [17] [18]. As an example, duty cycle methods, located on MAC layer, adapt the use of the hardware states (sleep, idle, ON...) with the application needs. Combined with the progress made to propose hardware running at lower power states [START_REF] Karray | A comprehensive survey on wireless sensor node hardware platforms[END_REF], the use of duty cycle seems to be the most efficient solution to save energy in WSN [START_REF] Rault | Energy efficiency in wireless sensor networks: A top-down survey[END_REF].

Consequently, several approaches of duty cycle have been proposed in the literature [START_REF] Memon | Optimal transmit power for channel access based wsn mac protocols[END_REF]. Because synchronization is energy intensive and difficult to deploy on WSN, the most adapted duty cycle techniques for WSN are asynchronous. In this context, Low Power Listening (LPL) solution is one of the most popular energy saving solutions [START_REF] Dinh | An adaptive low-power listening protocol for wireless sensor networks in noisy environments[END_REF] embedded as default solutions in the two common open source OS dedicated to WSN [START_REF] Wang | Review on open source operating systems for internet of things[END_REF], Contiki OS [START_REF] Uwase | Experimental comparison of radio duty cycling protocols for wireless sensor networks[END_REF] and Tiny OS [START_REF] Amjad | Tinyos-new trends, comparative views, and supported sensing applications: A review[END_REF]. In LPL, the node performs periodical wake-up to check the channel to detect possible communications from neighbor nodes. If a signal is detected, node stays awake to receive data and to route it if necessary. Otherwise, the node comes back to sleep state to save energy until the next channel check. By this mechanism, nodes can improve energy consumption by keeping network reliability. When a node wants to send, it just performs, before sending data, Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) protocol with Clear Channel Assessment (CCA) to be sure the media is free.

In this paper, performances of LPL based duty cycle solution are analyzed through the ContikiMAC [START_REF] Dunkels | The contikimac radio duty cycling protocol[END_REF] example. Wake-up interval called Channel Check Rate (CCR) determines the sleep/wake-up scheduling. It is predefined before WSN deployment and so it is static. Therefore, the impact of CCR on energy consumption and on Packet Rate Reception (PRR) and packet retransmissions are studied. Using the obtained results, shortcomings linked to CCR configuration are highlighted and solutions to improve LPL process are proposed and discussed.

The rest of this paper is organized as follows. In section II performance results obtained with our deployed platforms are described. Section III discusses countermeasures to improve LPL and the remaining issues. Then, we conclude and present future works.

II. PERFORMANCES ANALYSIS

In ContikiMAC, apart from application time, the duration the node can sleep to save energy is defined thanks to CCR. Different values of CCR can be configured. This CCR configuration must be made before node deployment and so it is static.

When nodes are in sleeping mode, no task is performed. Therefore, to study the impact of CCR values on WSN applications, important criterion to analyze are not only the energy consumption but also network performances such as PRR and the number of retransmitted application data. PRR represents the number of packets received compared to the number of packets sent. A 100% of PRR indicates application runs without disturbances. If no retransmission is necessary, more energy is saved. So, we study the impact of CCR values on these two parameters to quantify the QoS. An experimental testbed and a Cooja [START_REF] Osterlind | Crosslevel sensor network simulation with cooja[END_REF] simulation setup are proposed to analyze these performances. Table I summarizes the hardware used for each setup, the monitoring systems for energy and network performance evaluations. On testbed, we profile the global energy consumption of a XM1000 node. In this study, simulation platform allows us to have a more fine-grained analysis and to separate consumptions of MCU with RF (Radio ON, Receiver state (RX) and Transmitter state (TX)) but sensors and buses cannot be accessed. These missing components do not impact this study because CCR has no effect on them.

During experiments, after joining the network, End Device (ED), implementing ContikiOS 3.0, sends periodically sensors data (testbed) or a counter value (simulation) to a sink node. ContikiMAC wake-up is used as duty cycle solution on ED. Sink node keeps radio 100% ON.

A. Energy consumption investigation

Fig. 1a shows the energy profile obtained during sending data (application) phase with our experimental testbed for a node implementing ContikiMAC. As demonstrated, the Con-tikiMAC protocol performs two periodical consecutive CCA to check the media 1 . Next application starts and, at the end of 2 , the MCU is waked up. After that, before sending data, the node performs 6 CCA to be sure the media is free 3 . These 6 CCA are due to CSMA-CA protocol which is implemented as part of ContikiMAC protocol. Then the node sends its data 4 and switches on RX state to wait an acknowledgment 5 .

Finally, the MCU goes back to sleep mode 6 .

As illustrated by Fig. 1b, when ContikiMAC is enabled, the total energy can be divided approximately by 104 for CCR at 8Hz compared to No CCR. RF represents at least 70% of total energy consumption and until 99.7% when No CCR is used. RF spends the most energy in listening phase ( 1 & 6 of Fig. 1a). In case of No CCR, because MCU and RF are always ON, listen phase is 59.9mW against 0.335mW with CCR at 8Hz. Using Cooja setup, the percentage of time the radio spends in RX, TX or ON is shown in Table II for an application sending data every second with different values of CCR. The RX percentage stays equal to 0.04% (respectively 0.29% for TX) even when CCR changes. For the same application period, duty cycle (RF ON) increases with CCR from 1% to 10% in average. This phenomenon is explained by the listen phase which is multiplied by 7 in average when CCR changes from 8Hz to 128Hz. The node runs more often CCA to check the network which costs energy. Thus, a higher CCR implies a higher energy consumption.

At the origin, these different values of CCR allow to adapt the check frequency with the application needs and the network conditions (topologies, traffic, possible network congestion...) to offer correct QoS. Nevertheless, the obtained results demonstrate that CCR value has to be defined cautiously in the design phase because it could have a major impact on the energy consumption.

B. Network performances analysis

QoS values observed for the testbed are similar to them of simulation but, because network disruptions can deteriorate PRR and retransmissions, we use simulations to deploy repeatable WSN with no losing media to analyze only the impact of CCR values on the QoS.

First, using the scenario of section II-A, for all the values of CCR, PRR is equal to 100% and the retransmission is none. So, a CCR of 128Hz does not improve network performances in case of 1s application period and costs more energy consumption than 8Hz.

After that, the performances of WSN with a CCR defined lowly to save more energy and an application with high periodicity are studied. In this case, the CCR is configured at 4Hz and the application period is chosen below CCR period at 0.2s. Table III shows the PRR and the number of retransmitted data and routing frames (ReTX) for three kind of experiment. "CCR" entry indicates node with CCR at 4Hz, "NoCCR" entry is for node always ON and black grid is when node is not deployed on the experiment.

In Exp. 1, as sink node has no CCR, the PRR is 100%. We can observe 20% of packet retransmitted. This is due to the high frequency of the application. In Exp. 2, when sink node performs CCR too, the retransmission becomes 95.4%. This implies that the ED has no time to perform duty cycle between two transmissions. Nevertheless, the PRR stays high at 99.6%. If topology change as in Exp. 3 and a router R is placed between ED and a sink node always ON, 94.5% of frames are retransmitted for a PRR of 3.6%.

In conclusion, for network performances, when application period is high (1s), additional CCA linked with a higher CCR could be unnecessary in relation to the needs of protocols and application, costing more energy consumption without improving network performances. On the other hand, when CCR is defined inaccurately by choosing above period application to save energy or if network topology changes as in dynamic network, the static hard coded CCR, as demonstrated, is not adapted and the QoS performances can be disrupted. A lot of retransmission happened costing energy and disrupting duty cycle mechanism.

III. HOW TO IMPROVE ENERGY MANAGEMENT?

LPL solution is claimed as the best software solution in literature to improve energy consumption in WSN. Nevertheless, through the results obtained in section II-A, we shown radio energy consumption is multiplied by 7 for a CCR at 128Hz compared to a CCR at 8Hz. Moreover, network performances can be disrupted if CCR period is not adapted to network conditions, as shown in section II-B where PRR falls at 3.6% with 94.5% of retransmitted frames. So, these results demonstrate that static hard coded duty cycle is difficult to configure.

To limit the node energy consumption while keeping network performances suitable, one solution consists to update the value of the duty cycle in run time [START_REF] Dinh | An adaptive low-power listening protocol for wireless sensor networks in noisy environments[END_REF]. This dynamic solution can be based on application needs [START_REF] Yadav | Performance and analysis of mac protocols based on application[END_REF], traffic conditions [START_REF] Siddiqui | Adp-mac: An adaptive and dynamic polling-based mac protocol for wireless sensor networks[END_REF] or incoming/outgoing packet rate [START_REF] Ayele | Adaptive sleep-time management model for wsns[END_REF], or considering the battery capacity level [START_REF] Segura | Duty cycle based energy management tool for wireless sensor networks[END_REF]- [START_REF] Galmés | Analytical model for the duty cycle in solarbased eh-wsn for environmental monitoring[END_REF]. Nevertheless, all the previous LPL dynamic solutions use only one unique parameter to update their duty cycle.

Therefore, to preserve more energy, one solution could be to use a multi-parameter dynamic duty cycle. With the monitoring of parameters coming from different sources (sensors, application, hardware, batteries...) and a decision algorithm, the duty cycle can be dynamically managed on run time. This solution allows to take into account more phenomenon linked with the several dynamic changes happening in WSN to adapt the sleep period and so, to save more energy.

Nevertheless, multi-parameter dynamic duty cycle needs to monitor all the previously mentioned parameters. It requires hardware and software tools to collect and provide these data to the decision algorithm. Secondly, this duty cycle updating must be less energy costly than the use of a static one. So, the cost of this new process must be evaluated, and the policy must be determined. Finally, updated duty cycle has to be computed autonomously by the nodes to save more energy. This non-unified duty cycle value can cause missing neighbor communications, retransmissions needs and poor network performances. These issues stay open.

IV. CONCLUSION AND FUTURE WORK

In this article, we shown that when LPL solution is deployed to reduce the listening phase, the static hard coded value of the wake-up period performs unnecessary channel checks and so costs energy consumptions. Moreover, a bad configuration can cause poor network performances. To counter these issues, we have discussed the necessity to propose dynamic duty cycle solutions. Our future work will be dedicated to deployed multi-parameters dynamic duty cycle in Contiki OS. Moreover, to enable our solution to run, issues linked with non-unified duty cycle should be resolved. Work will also be made on development of tools for monitoring parameters useful for the dynamic update of the duty cycle. Monitoring and decision costs will be evaluated to choose the best policy.

  (a) Profile obtained with real testbed. (b) Energy consumption from collect view tool.

Fig. 1 .

 1 Fig. 1. Energy consumption results.

TABLE I DESCRIPTION

 I OF THE EXPERIMENTAL ENVIRONMENTS.

		Testbed	Simulation
	Node Hardware	XM1000 [26]	Z1 [27]
	Energy Monitoring System	1Ω shunt resistor 5% AOP AD620ANZ [28]	Cooja Collect View
		Osc. Tektronic MSO 2014 [29]	[30]
	QoS Monitoring System	Sniffer + Wireshark [31]	Python software


Hu Zhaoyu

Mounir Benkoulouche

Louis-Antoine Barel

Guillaume Le Heiget

Ben Akli

Yann Imeddourene

Nelly Le Guen

Catherine Monties

Magali Remaud Guerreiro

Claire Simeon

Moulis

A convergent chemoenzymatic strategy to deliver a diversity of Shigella flexneri serotype-specific O-antigen segments from a unique lightly protected tetrasaccharide core

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.