METHOD FOR PRODUCING A COMB POLYMER AND ITS USE FOR PRODUCING A SOLID ELECTROLYTE

Description

Technical field

[0001] The present invention relates to a novel method for preparing a comb polymer, and to the comb polymer thus obtained.

[0002] Such comb polymers can be used, in combination with alkali or alkaline earth metal salts, to form solid electrolytes, which find particularly advantageous applications in different electrochemical systems or devices, in particular in rechargeable batteries, for example lithium batteries. Prior art

[0003] Classically, the operating principle of an electrochemical generator is based on the insertion and removal, also called "deinsertion", of an alkali metal ion or a proton, into and from the positive electrode, and the deposition or extraction of this ion, onto and from the negative electrode.

[0004] The main systems use the lithium cation as the transport ionic species. In the case of a lithium accumulator, for example, the lithium cation extracted from the positive electrode during battery charging is deposited on the negative electrode, and conversely, it is extracted from the negative electrode to be intercalated in the positive electrode during discharge.

[0005] The transport of the proton or the alkali or alkaline-earth cation, in particular the lithium cation, between the positive electrode and the negative electrode, is ensured by an ionic conductive electrolyte.

[0006] The formulation of the electrolyte used is essential for the performance of the electrochemical system, particularly when it is used at very low or very high temperatures. The ionic conductivity of the electrolyte determines the efficiency of the electrochemical system, given that it affects the mobility of ions between the positive and negative electrodes. Other parameters also play a role in the choice of the electrolyte used. These include its thermal, chemical or electrochemical stability within the electrochemical system, as well as economic, safety and environmental criteria, including the toxicity of the electrolyte.

[0007] Conventional electrolytes are typically produced by dissolving a metal cation salt in an organic or aqueous medium, and require a separator to provide insulation between the anode and the cathode for the development of a complete electrochemical system.

[0008] As such, solid-state electrolytes (SSEs) represent one of the most promising alternatives to conventional electrolytes. Lithium batteries, using solid-state electrolytes, are considered the next generation of energy storage devices, allowing higher energy densities and increased safety due to the absence of solvents. SSEs can be classified into three categories: inorganic solid electrolytes (ISEs), polymeric solid electrolytes (SPEs) and hybrid solid electrolytes (HSEs).Particular attention is paid to SPEs and HSEs, solid polymer-based electrolytes, due to the high flexibility of these electrolytes, which allows their use in the development of batteries with reduced thickness and greater flexibility.

[0009] Similar to a liquid electrolyte, these polymer-based solid electrolytes are composed of a host polymer in which an alkali or alkaline earth metal salt is dissolved. Historically, the most widespread SPEs and HSEs, particularly for lithium electrochemical devices, have been based on polyethers, and more specifically on poly(ethylene glycol), also called poly(oxyethylene) (POE) [1]. However, the use of this type of polymer has several limitations. In particular, POE is largely crystalline (the crystallinity of pure POE is around 75-80% at room temperature), which leads to a loss of ionic conductivity of the POE-based solid electrolyte below its melting temperature (around 60-65°C). The mechanical stability of POE is also insufficient at high temperatures (above 60°C) where it conducts ions well. Moreover, POE has a narrow electrochemical stability window (< 3.9 V vs.Li / Li +< ), which makes this type of SPEs suitable only for their implementation with low potential cathodes, such as LiFePO 4 (LFP) type.

[0010] In fact, alternative polymers have been developed in recent years, including polycarbonates and more specifically poly(trimethylene carbonate) (PTMC). PTMC provides improved performance compared to POE in terms of electrochemical stability (up to 5.0 V vs. Li / Li +< ), higher ion transport number (t + ≈0.8) and thermal stability. However, these polymers have limited mechanical performance.

[0011] In order to overcome these limitations, it has been proposed to synthesize copolymers [2-4], comprising a rigid block, providing mechanical properties suitable for their use as an electrolyte, and an ionically conductive block. These copolymers can be of the block copolymer type formed from different polymers or of the graft copolymer type, also called comb polymers, composed of a main polymer chain, onto which pendant polymer chains are grafted.

[0012] Recently, the synthesis of comb polymers comprising a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) main chain carrying poly(ethylene oxide) or poly(trimethylene carbonate) side chains, grafted in para pentafluorophenyl groups of the main chain via ether linkages [5-6].

[0013] Other examples of comb polymers comprising a main chain formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers bearing side chains are described in Ott et al., Chem. Comm., 30: 3516-3518 (2008) and Prithwira et al., ACS Applied Energy Materials, 5: 15520-15528 (2022). Polymers formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers are also described in the articles by Cai et al., Polymer Chemistry, 3: 1061-1068 (2012), Cho et al., Polymers, 12: 1-14 (2020) and Jing Chen et al., Polymer, 54: 3757-3766 (2013). The article by Guillaume Delaittre et al., 9:2679-2684 (2018) relates to the reaction para -fluoro-thiol.

[0014] These comb polymers can be formed, for example, by grafting hydroxyl functions onto the benzene rings of the PPFS monomeric units, for example, by reacting the PPFS polymer with potassium hydroxide in the presence of water, followed by polymerization of the side chains directly at the hydroxyl-functionalized PPFS polymer. The grafted hydroxyl functions, however, have limited accessibility during the subsequent polymerization of the side polymer chains, leading to a loss of control over the comb polymer structure.

[0015] There remains a need to propose a new route for the synthesis of comb-shaped ionic conductive polymers, making it possible to improve the control of the characteristics of the polymers obtained, in particular in terms of grafting rate, chain length and polydispersity of the pendant chains, and thus to optimize the performance of the solid electrolytes formed from these polymers.

[0016] The present invention aims precisely to meet this need. Statement of the invention

[0017] The invention thus relates, according to a first of its aspects, to a process for preparing a comb polymer comprising at least the steps consisting of: (i) having a polymer formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, called a “PPFS-type polymer”, intended to form the main chain of the comb polymer; (ii) functionalizing a portion of the pentafluorophenyl groups of the monomeric units of the PPFS-type polymer with pendant hydroxyl functions, by reacting said PPFS-type polymer with at least one molecule, called a “mercapto-alcohol”, comprising one or more free hydroxyl functions, preferably a single free hydroxyl function, and a free thiol function, said functionalization involving a nucleophilic substitution reaction between the fluorine atom in position paraof the pentafluorophenyl group and the thiol function carried by said mercapto-alcohol; and (iii) proceeding with the formation of polyester / polycarbonate type side chains on the functionalized PPFS polymer obtained in step (ii), by ring-opening polymerization from at least one cyclic monomer of five to eight members chosen from lactones and cyclic carbonates.

[0018] A "comb polymer," also known as a branched or branched copolymer, means a polymer that has a linear polymeric main chain and at least two side chains or pendant chains attached to the main chain at points between the two ends of the main chain, called branch points or branch points. Unlike linear polymers that have non-polymeric side groups or pendant groups, the side chains of comb polymers are oligomers, polymers, or copolymers.

[0019] In particular, a comb polymer is distinct from so-called hyperbranched or hyper-ramified polymer networks. In particular, the side polymer chains carried by the main chain of the comb polymer according to the invention do not themselves carry side polymer chains.

[0020] In the remainder of the text, the comb polymer obtained according to the invention will be referred to more simply as “comb polymer” or “comb polymer”.

[0021] In the present description, in the absence of contrary indications, the term "polymer" will be used to designate, in the broad sense, both homopolymers and copolymers. By "copolymer" is meant a polymer derived from at least two different species of monomers.

[0022] In the context of the present invention, the term "monomer unit" means the smallest constituent unit whose repetition leads to a polymer chain.

[0023] By "polyester / polycarbonate side chain" or more simply "polyester / polycarbonate chain" is meant a polymer chain obtained from one or more cyclic monomers with five to eight members chosen from lactones and cyclic carbonates. It may in particular be a homopolymer type chain, for example a polycarbonate chain obtained from the polymerization of a cyclic carbonate, or a polyester chain obtained from the polymerization of a lactone, or a copolymer type chain, obtained from the polymerization of at least two different cyclic monomers.

[0024] At the end of the functionalization step (ii) of the process of the invention, the PPFS type polymer thus has free hydroxyl functions linked in position para of a part of the pentafluorophenyl groups via thioether bonds.

[0025] The hydroxyl functions grafted onto the PPFS-type polymer will be used in step (iii) to initiate the ring-opening polymerization reaction. The PPFS-type polymer thus functionalized by hydroxyl functions thus serves as a “macro-initiator” for the polymerization of the side chains of the comb polymer according to the invention.

[0026] At the end of the polymerization step (iii) of the process of the invention, the PPFS type polymer thus has polycarbonate / polyester chains linked in position para of a part of the pentafluorophenyl groups via thioether bonds.

[0027] The invention thus relates, according to another of its aspects, to a comb polymer, in particular as obtained according to the process of the invention described above, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomeric units of the main chain carrying polymeric side chains, called polycarbonate / polyester chains, formed from at least one cyclic monomer of five to eight members chosen from lactones and cyclic carbonates; said polymeric side chains being grafted in para pentafluorophenyl groups via thioether bonds.

[0028] In particular, said polycarbonate / polyester chains are poly(trimethylene carbonate) (PTMC) or poly(ε-caprolactone) (PCL) chains, in particular having hydroxyl functions at the chain end in protected form, resulting from the reaction of said hydroxyl function with a protective agent as detailed in the rest of the text.

[0029] Preferably, as detailed in the rest of the text, the nucleophilic substitution reaction for the grafting of the mercapto-alcohol at the level of the PPFS type polymer in step (ii) is carried out in the presence of a weak aprotic base. Advantageously, the use of a weak base allows a substitution in para chemoselective pentafluorophenyl groups and thus good control of the grafting of the mercato-alcohol, only the thiol function reacting in the presence of a weak base and only the fluorine atom in para pentafluorophenyl groups are substituted.

[0030] The nucleophilic substitution reaction for grafting the mercapto-alcohol to the PPFS-type polymer in step (ii) is thus carried out in the presence of an aprotic base weaker than sodium hydride (NaH), sodium hydroxide and potassium hydroxide, preferably an aprotic base having a pKa strictly less than 15 and strictly greater than 10. In particular, the nucleophilic substitution reaction can be carried out in the presence of a base having a pKa strictly less than 14, more particularly less than or equal to 13 and strictly greater than 10, or even between 10.2 and 13, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethylamine (TEA) or potassium carbonate (K 2 CO 3 ), in particular DBU or TEA.

[0031] Advantageously, the method of the invention allows excellent control of the grafting rate of the polycarbonate / polyester type side chains. The grafting rate can be more particularly adjusted by varying the molar ratio between the mercapto-alcohol and the monomeric units of the PPFS type polymer during the functionalization step (ii). Preferably, as detailed in the rest of the text, the molar grafting rate obtained in step (ii) of said mercapto-alcohol at the level of the PPFS type polymer does not exceed 35%, to ensure good solubilization of said functionalized PPFS type polymer, called “macro-initiator”, in the solvent medium used for the polymerization of the side chains in step (iii).

[0032] Thus, the molar grafting rate of the polycarbonate / polyester side chains of the comb polymer obtained according to the invention is preferably between 1% and 35%, in particular between 5% and 35%.

[0033] Advantageously, the functionalization of the PPFS type polymer by the use of a mercapto-alcohol allows the hydroxyl function to be more accessible for the polymerization of the side chains.

[0034] Also, the method according to the invention allows excellent control of the polymerization of the side chains, in particular of the molar mass and the polydispersity of the polycarbonate / polyester chains obtained.

[0035] In particular, the process of the invention allows a large variability of the number-average molar mass in side chains of the comb polymer obtained. The number-average molar mass can be more particularly adjusted by varying, in step (iii), the molar ratio between the cyclic monomers and the hydroxyl functions grafted onto the PPFS.

[0036] In particular, the number-average molar mass Mn of the polycarbonate / polyester side chains may thus be between 800 g.mol -1< and 10,000 g.mol -1< . Advantageously, the number-average molar mass may be less than or equal to 2000 g.mol -1< , in particular between 800 g.mol -1< and 2000 g.mol -1< and more particularly between 800 g.mol -1< and 1500 g.mol -1< .

[0037] Furthermore, as detailed in the remainder of the text, the inventors have advantageously developed a method for purifying the comb polymer obtained according to the invention, which is easy to implement and makes it possible to eliminate the polycarbonate / polyester chains which have not been grafted onto the PPFS type polymer.

[0038] The method of synthesizing the side chains of the comb polymer according to the invention, associated with a purification of the product obtained, makes it possible to access, in a reproducible manner, comb polymers of good purity and controlled structure, in particular having grafted chains of controlled molar mass and low polydispersity.

[0039] It is thus possible to vary the characteristics of the comb polymer, in particular in terms of the length of the side chains, so as to optimize the performance of the solid electrolyte formed from these polymers.

[0040] Advantageously, the hydroxyl functions at the ends of the grafted polycarbonate / polyester chains of the comb polymer according to the invention are protected. As detailed in the rest of the text, the protection of the hydroxyl functions can be more particularly carried out at the level of the comb polymer obtained, before or after purification, by reaction of said hydroxyl function(s) at the ends of the side polycarbonate / polyester chains, with at least one compound, called a protective agent, chosen from acyl chlorides, acid anhydrides and isocyanates.

[0041] The comb polymers according to the invention find particularly advantageous applications for forming, in combination with at least one alkali or alkaline-earth metal salt, a solid electrolyte.

[0042] By "solid electrolyte" is meant an electrolyte excluding the presence of a component in liquid form, and acting both as a separator and as an ionic conductor in an electrochemical system. The solid electrolyte according to the invention is more particularly in the form of a solid electrolytic film or membrane in an electrochemical system.

[0043] As detailed in the remainder of the text, the solid electrolytes prepared according to the invention may be of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type. The solid electrolyte films or membranes prepared according to the invention advantageously exhibit good flexibility.

[0044] The invention thus relates, according to another of its aspects, to the use of at least one comb polymer according to the invention, in particular as obtained according to the process of the invention, to form, in combination with at least one alkali or alkaline-earth metal salt, a solid electrolyte intended for an electrochemical system, in particular for a rechargeable battery, in particular a lithium battery.

[0045] The invention also relates to a solid electrolyte, in particular of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type, comprising, or even being formed from: at least one comb polymer according to the invention, in particular obtained according to the process of the invention, preferably the hydroxyl functions of which at the ends of the grafted side chains are protected; at least one alkali or alkaline-earth metal salt, in particular a lithium salt; and optionally one or more inorganic fillers, in particular chosen from the conductive fillers and the non-conductive fillers of the alkali or alkaline-earth cation(s), in particular lithium.

[0046] The solid electrolytes formed according to the invention can find applications in various electrochemical systems, in particular in energy storage systems, in particular in rechargeable batteries, in particular lithium batteries.

[0047] Thus, the invention also relates to the use of a solid electrolyte according to the invention in an electrochemical system, in particular in a lithium battery.

[0048] It also relates to an electrochemical system, in particular an energy storage device, in particular a rechargeable battery, in particular a lithium battery, in particular a lithium-ion or lithium-metal battery, comprising a solid electrolyte, in particular a solid electrolyte film as defined previously.

[0049] As illustrated in the examples which follow, the solid electrolytes obtained from the comb polymers according to the invention lead to lithium batteries having excellent performances, in particular a high ionic conductivity, for example greater than or equal to 10 -7< S.cm -1< at 60°C, in particular greater than or equal to 10 -6< S.cm -1< , advantageously greater than or equal to 10 -5< S.cm -1< .

[0050] The solid electrolytes prepared from the comb polymers according to the invention also exhibit good mechanical strength and high thermal stability (which ensures the safety of the energy storage devices comprising them).

[0051] An electrochemical system, for example a lithium battery, comprising a solid electrolyte according to the invention, can operate over a wide temperature range, preferably between 20°C and 100°C, more preferably between 40°C and 80°C.

[0052] Advantageously, a solid electrolyte based on a comb polymer according to the invention, in particular comprising PTMC type side chains, can be advantageously implemented in high energy density batteries, in combination with so-called "high" potential positive electrodes, i.e. operating at a potential difference greater than 4 V versus Li / Li +< , such as Li 0< vs. LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 batteries, without impacting the thermal and electrochemical stability of the electrolyte.

[0053] Other characteristics, variants and advantages of the process for preparing a comb polymer according to the invention, of the comb polymer obtained and of its implementation in an electrochemical system, will emerge more clearly on reading the description, examples and figures which follow, given for illustrative and non-limiting purposes of the invention.

[0054] In the context of the invention, the following terms are understood to mean: “C tz” where t and z are integers, a carbon chain which may have from t to z carbon atoms; for example C 1-4 a carbon chain which may have from 1 to 4 carbon atoms; “alkyl”, a saturated aliphatic group, linear or branched; for example a C 1-4 -alkyl group represents a carbon chain of 1 to 4 carbon atoms, linear or branched, more particularly a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl; "alkylene", a saturated, linear or branched, divalent radical derived from an alkyl. For example, a C 1 -C 3 -alkylene group represents a saturated, linear or branched carbon chain of 1 to 3 carbon atoms, for example methylene, ethylene, 1-methylethylene or propylene. "polycyclic group", a group having two or more nuclei (cycles), fused (ortho-fused or ortho- and peri-fused) to each other, i.e. having, two by two, at least two carbons in common. "heterocycle", a cyclic group, preferably 4-, 5- or 6-membered, comprising one or more heteroatoms, in particular chosen from oxygen, sulfur and nitrogen. The mono- or poly(hetero)cyclic groups according to the invention may be unsaturated, partially saturated or saturated. An aromatic cycle can be benzene in particular.

[0055] In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated. Brief description of the drawings

[0056] [ Fig 1 ] represents the intensity of the measurement signal obtained by nuclear magnetic resonance (NMR) of 19< F as a function of the chemical shift, expressed in ppm, for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-03") synthesized in Example 1.1. [ Fig 2] represents the elution diagram obtained by Size Exclusion Chromatography (SEC) in THF at 30°C (TDS calibration), as a function of the retention volume, obtained for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-03") synthesized in Example 1.1. The ordinate represents the detection obtained by an intrinsic viscosity detector (IV-DP), low angle light scattering (LALS), right angle light scattering (RALS), and a refractomer (RI). [ Fig 3 ] represents the elution diagram obtained by CES (THF, 30°C, TDS calibration), as a function of the retention volume, obtained for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-Em-01") synthesized in example 1.2. [ Fig 4] represents the intensity of the measurement signal obtained by nuclear magnetic resonance (NMR) of 19< F as a function of the chemical shift, expressed in ppm, for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-Em-01") synthesized in example 1.2. [ Fig 5 ] represents the intensity of the measurement signal obtained by 19< F NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) functionalized by 6-mercaptohexan-1-ol ("PPFS-gS-OH-01") synthesized in example 2.1. [ Fig 6 ] represents the intensity of the measurement signal obtained by 19< F NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) functionalized by 6-mercaptohexan-1-ol ("PPFS-gS-OH-02") synthesized in example 2.2. [ Fig 7] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-03") synthesized in example 3.1. [ Fig 8 ] represents the elution diagram obtained CES (THF, 30°C, TDS calibration), as a function of the retention volume, for the comb copolymer poly(2,3,4,5,6-pentafluorostyrene) carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-03") synthesized in example 3.1. [ Fig 9 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-04") synthesized in example 3.2. [ Fig 10] represents the elution diagram obtained CES (THF, 30°C, TDS calibration), as a function of the retention volume, for the comb copolymer poly(2,3,4,5,6-pentafluorostyrene) carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-04") synthesized in example 3.2. [ Fig 11 ] represents the evolution of the ionic conductivity (in S.cm -1< ) ​​as a function of the temperature (T in °C, and 1000 / T, T being expressed in degrees Kelvin) for the solid electrolytes based on the comb polymers "PPFS-g 0.2 -S-PTMC 1000 -OH" and "PPFS-g 0.2 -S-PTMC 800 -OH" prepared according to example 4. Detailed description COMB POLYMER (i) PPFS type polymer intended to form the main chain of the comb polymer

[0057] As mentioned above, the comb polymer according to the invention is formed from a polymer obtained from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, and intended to form the main chain of the comb polymer.

[0058] The PPFS type polymer can be a homopolymer or a copolymer.

[0059] The monomers of the type 1-ethenyl-2,3,4,5,6-pentafluorobenzene, also more commonly called 2,3,4,5,6-pentafluorostyrene (PFS) and 1-allyl-2,3,4,5,6-pentafluorobenzene (IUPAC name 1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene) correspond to the following formula (M1): in which e is 0 (case of pentafluorostyrene) or e is 1 (case of 1-allyl-2,3,4,5,6-pentafluorobenzene).

[0060] Preferably, the PPFS type polymer is a homopolymer.

[0061] For example, the PPFS-type polymer may be a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) or a poly(1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene), preferably a poly(2,3,4,5,6-pentafluorostyrene).

[0062] For the purposes of simplification, polymers derived from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, in particular of the poly(2,3,4,5,6-pentafluorostyrene) or poly(1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene) type, are more simply referred to as “pentafluorostyrene-type polymer” or “PPFS-type polymer”.

[0063] The PPFS type polymer used to form the main chain of a comb polymer according to the invention advantageously has a number-average molar mass M n greater than or equal to 10,000 g.mol -1< , in particular between 10,000 g.mol -1< and 1,000,000 g.mol -1< , in particular between 40,000 g.mol -1< and 600,000 g.mol -1< , more particularly between 40,000 g.mol -1< and 400,000 g.mol -1< , or even between 50,000 g.mol -1< and 100,000 g.mol -1< .

[0064] The number-average molecular mass, also called number-average molar mass, of a PPFS-type polymer can be determined by size exclusion chromatography (SEC), preferably with TDS calibration.

[0065] In particular, the number-average degree of polymerization of the PPFS-type polymer, corresponding to the number of monomer units constituting the polymer, may be greater than or equal to 50, in particular between 50 and 4,200 and more particularly between 50 and 520.

[0066] According to a particular embodiment, the PPFS type polymer intended to form the main chain of a comb polymer according to the invention is a poly(2,3,4,5,6-pentafluorostyrene) (PPFS), in particular having a number-average molecular mass of between 10,000 g.mol -1< and 600,000 g.mol -1< and more particularly between 40,000 g.mol -1< and 100,000 g.mol -1<.

[0067] Preferably, the length of the PPFS type polymer, intended to form the main chain of the comb polymer according to the invention, in other words the degree of polymerization of the PPFS type polymer forming the main chain of the comb polymer according to the invention, is sufficiently high, so that the comb polymer formed according to the invention has a molar mass greater than the so-called critical entanglement molar mass.

[0068] The critical entanglement molar mass, denoted M c , for a given polymer, is generally defined as the mass from which the dynamics of the polymer is in a crawling regime. This critical entanglement molar mass can be determined empirically by methods known to those skilled in the art.

[0069] Controlling the average molecular mass of the comb polymer according to the invention makes it possible to control the mechanical properties of the comb polymer obtained, and in particular its viscoelasticity properties.

[0070] The comb polymer according to the invention is advantageously capable of forming a three-dimensional network, resulting from the entanglement of the polymer chains, and has a rubbery plateau identifiable for example by rheological measurements (for example, Young's modulus and shear modulus measured in multi-frequency dynamic mechanical analysis) on the polymer formed.

[0071] In a particular embodiment, the PPFS type polymer corresponds to the following formula (I): in which e is 0 or 1; s represents the number of monomeric units of the PPFS type polymer (corresponding to the degree of polymerization), in particular s is greater than or equal to 50, in particular between 50 and 4,200.

[0072] The PPFS type polymer used in the process according to the invention, intended to form the main chain of a comb polymer according to the invention, can be obtained beforehand by synthesis methods known to those skilled in the art. For example, it can be synthesized by a radical polymerization method, in particular by controlled radical polymerization, as described for example by Atanasov et al. [7].

[0073] Alternatively, it can be synthesized by Ziegler-Natta catalysis. Ziegler-Natta polymerization processes are well known for example for the synthesis of polystyrene [8]. They have been described in the case of the synthesis of PPFS in EP 3 763 748 A1 [9].

[0074] Advantageously, synthesis by Ziegler-Natta catalysis makes it possible to produce polymers with average molecular masses and adjustable dispersity, with good yields.

[0075] The PPFS type polymer can thus be formed by polymerization from the mixture of a Ziegler Natta type catalytic system comprising a catalyst and a co-catalyst; and 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers.

[0076] This synthesis method includes more specifically: bringing into contact a Ziegler Natta type catalytic system comprising a catalyst and a co-catalyst; with monomers of formula (M1) above; exposing the mixture thus formed to stirring and heating conditions conducive to the polymerization of said monomers.

[0077] The Ziegler-Natta type catalytic system can be of any generation, i.e. 1, 2, 3, 4 or later. Said catalytic system can be supported, homogeneous or heterogeneous.

[0078] The Ziegler Natta type catalytic system used for the synthesis of the PPFS type polymer can include: a catalyst containing a derivative, in particular a halide or an alcoholate, of a transition metal from group IV, V or VI of the periodic table of elements, preferably chosen from titanium, zirconium, vanadium, cobalt, chromium and nickel; and a co-catalyst containing a hydride or an alkyl derivative of an element from columns 1, 2 or 13 of the periodic table of elements, and preferably containing a hydride or an alkyl derivative of aluminium.

[0079] According to a particular variant of this embodiment, the catalyst containing a derivative of a transition metal from group IV, V or VI of the periodic table of elements is chosen from TiCl 4 , TiCl 3 , VCl 3 , VCl 4 , CoCl 2 , Ti(OBu) 4 and Cr(acac) 3 .

[0080] In particular, the co-catalyst containing a hydride or an alkyl derivative of an element from columns 1, 2 or 13 of the periodic table of elements is chosen from AlEt 3 , AlEt 2 Cl, AlEtCl, AlEtCl 2 , AlBu 3 , GaEt 3 and BeEt 2 . Preferably, according to this embodiment, the catalytic system is chosen from TiCl 4 / AlEt 3 , TiCl 3 / AlEt 2 Cl, TiCl 3 / GaEt 3 , TiCl 3 / BeEt 2 , VCl 4 / AlEt 2 Cl, CoCl 2 / AlEtCl, VCl 3 / AlEt 3 , Ti(OBu) 4 / AlEt 3 , Cr(acac) 3 / AlEt 3 , and even more preferably is TiCl 4 / AlEt 3 .

[0081] Such a Ziegler-Natta type catalytic system can be prepared, for example, by adding triethyl aluminum to titanium chloride and then allowing the mixture to stabilize for 30 minutes.

[0082] Alternatively, the Ziegler-Natta type catalytic system may comprise: TiCl 4 supported on MgCl 2 as catalyst; and AlEt 3 as co-catalyst.

[0083] Alternatively, the Ziegler Natta type catalytic system may comprise: a catalyst selected from metallocenes; and a co-catalyst selected from methylaluminoxane (MAO), Ph 3 C +< B(C 6 F 5 ) 4 -< and B(C 6 F 5 ) 3 .

[0084] Preferably, according to this embodiment, the catalytic system is chosen from ZrCp 2 Cl 2 / MAO, ZrCp 2 Cl 2 / B(C 6 F 5 ) 3 , ZrCp 2 Cl 2 / Ph 3 C +< B(C 6 F 5 ) 4 -< , CpTiCl 3 / MAO, and

[0085] According to a preferred embodiment, the catalyst / co-catalyst molar ratio is between 0.3 and 10, preferably between 0.5 and 2.

[0086] The contacting of a Ziegler-Natta type catalytic system, in particular as defined above, with the monomers of formula (M1) above can be carried out by simple mixing, in the presence or absence of a solvent such as fluorobenzene or tetrahydrofuran. The molar ratio of monomers (M1) / catalytic system can be between 10 and 1000, in particular between 10 and 250.

[0087] The mixture is then exposed to stirring and heating conditions conducive to the polymerization of the monomers (M1). In particular, the mixture may be exposed to a temperature level of between 60°C and 80°C, in particular for a period of at least 10 hours. Stirring may be carried out manually or mechanically, in particular using a conventional stirring device.

[0088] Preferably, the synthesis of the PPFS-type polymer is followed by a step of neutralization of the catalyst, for example with ethanol, then filtration of the catalytic system. The PPFS-type polymer thus formed can be precipitated, for example in methanol. (ii) Functionalization of the PPFS-type polymer by pendant hydroxyl functions

[0089] As mentioned previously, the PPFS type polymer is functionalized by pendant hydroxyl functions, via grafting in position para of a part of the pentafluorophenyl groups of the monomeric units of the PPFS type polymer, of at least one molecule comprising one or more free hydroxyl functions and a free thiol function.

[0090] In the remainder of the text, the term “mecapto-alcohol” refers to such a molecule comprising one or more free hydroxyl functions (either a mono- or poly-alcohol), preferably a single free hydroxyl function (mono-alcohol) and a free thiol function.

[0091] By free thiol function is meant an unprotected -SH function, which can react by nucleophilic substitution with a fluorine function under the conditions described in the rest of the text. By free hydroxyl function is meant an unprotected -OH function.

[0092] Preferably, the functionalization uses one or more mercapto-alcohols comprising a single free hydroxyl function.

[0093] Preferably, said mercapto-alcohol(s) used for the functionalization of a PPFS-type polymer according to the invention are chosen from mercapto-alkanols, in particular of formula: [Chem 4] HS-(CH 2 ) q -CH 2 -OH, in which: q is 0 or is an integer between 1 and 10, in particular between 3 and 7, preferably is 5.

[0094] The mercapto alcohol may be chosen, for example, from 4-mercaptobutan-1-ol, 5-mercaptopentan-1-ol, 6-mercaptohexan-1-ol and 7-mercaptoheptan-1-ol. For example, the mercapto alcohol is 6-mercaptohexan-1-ol.

[0095] It is understood that the method may implement one or more distinct mercapto-alcohols according to the invention. Preferably, the method of the invention implements a single mercapto-alcohol, in particular as described above.

[0096] The functionalization of the PPFS type polymer by pendant hydroxyl functions is more particularly carried out by nucleophilic substitution between the thiol function carried by the mercapto-alcohol, in particular as described previously, and the fluorine atom in position para of a pentafluorophenyl group.

[0097] This nucleophilic substitution reaction is regioselective, meaning that only the fluorine atom in position paraof a pentafluorophenyl group is substituted. Such a nucleophilic substitution reaction between a fluorine atom and a thiol function has for example been described for the grafting of a perfluorinated decanethiol or a mercapto-propanoic or mercapto-acetic acid onto a PPFS type polymer [10,11].

[0098] The nucleophilic substitution reaction for the functionalization of the PPFS-type polymer is more particularly carried out in the presence of a base. Advantageously, it is carried out in the presence of an aprotic base weaker than sodium hydride (NaH), sodium hydroxide (NaOH) and potassium hydroxide (KOH), preferably an aprotic base having a pKa strictly less than 15 and strictly greater than 10, in particular strictly less than 14, more particularly less than or equal to 13 and strictly greater than 10, or even between 10.2 and 13.

[0099] Advantageously, the nucleophilic substitution reaction for the functionalization of the PPFS type polymer is carried out in the presence of a base chosen from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, or IUPAC name 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine), triethylamine (TEA) and potassium carbonate (K 2 CO 3 ), in particular chosen from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and triethylamine (TEA). More preferably, the base is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0100] In particular, the base can be implemented in a base / mercapto-alcohol molar ratio of between 0.1 and 1.

[0101] The substitution reaction for the functionalization of the PPFS-type polymer can be more particularly carried out in a solvent medium. The solvent medium makes it possible to solubilize the PPFS-type polymer and the mercapto-alcohol. It can be formed from one or more aprotic polar solvent(s), in particular chosen from tetrahydrofuran (THF), amides such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP); methyl ethyl ketone (MEK), N-methyl-2-pyrrolidone and mixtures thereof, preferably tetrahydrofuran (THF), N,N-dimethylformamide (DMF) or methyl ethyl ketone (MEK), more preferably methyl ethyl ketone (MEK).

[0102] The substitution reaction may be carried out at a temperature between 10°C and 100°C, in particular between 15°C and 40°C, preferably between 20°C and 30°C, for example at room temperature. The reaction time may be between 1 hour and 16 hours, in particular between 6 hours and 16 hours.

[0103] Preferably, the reaction medium is kept stirring during the substitution reaction.

[0104] The polymer obtained following grafting of the mercapto-alcohol onto the PPFS type polymer is designated in the remainder of the text as “macro-initiator”, in that it comprises free, pendant hydroxyl functions in position para of a part of the pentafluorophenyl groups of the monomeric units, and intended to initiate the polymerization by ring opening for the formation of the side polymer chains in step (iii).

[0105] The grafting rate of the polycarbonate / polyester side chains of the comb polymer prepared according to the process of the invention can thus be controlled by the grafting rate of said mercapto-alcohol at the level of the PPFS type polymer in step (ii) of the process of the invention. The molar grafting rate is defined as the percentage of repeating units of the main chain of the PPFS type carrying a group or a pendant chain. The molar grafting rate, also called the substitution rate, can be characterized by nuclear magnetic resonance (NMR) of fluorine F 19<.

[0106] The grafting rate can be more particularly adjusted by varying the molar ratio between the mercapto-alcohol and the monomeric units of the PPFS-type polymer. In particular, said mercapto-alcohol(s) and said PPFS-type polymer can be used in a molar ratio of mercapto-alcohol(s) / monomeric units of the PPFS-type polymer of between 0.05 and 0.5, in particular between 0.1 and 0.5.

[0107] Preferably, the molar grafting rate obtained in step (ii) of said mercapto-alcohol at the level of the PPFS-type polymer is less than or equal to 35%, in order to allow the solubilization of the functionalized PPFS-type polymer, serving as macro-initiator, in the solvent medium used for the polymerization of the side chains in step (iii), in particular as described below. Advantageously, the molar grafting rate can thus be between 1% and 35%, in particular between 5% and 35%. In particular, the grafting rate can be between 10% and 30%.

[0108] The free hydroxyl functions of the macro-initiator derived from the mercapto-alcohol advantageously have good accessibility to initiate the polymerization of the side chains by ring opening.

[0109] Following the nucleophilic substitution reaction, the functionalized PPFS-type polymer can be recovered by precipitation in a solvent such as methanol.

[0110] In a particular embodiment, the monomeric units of the functionalized PPFS type polymer, obtained at the end of step (ii) of the process of the invention, correspond to the following formula (II): in which e and q are as defined previously.

[0111] In a preferred embodiment, the functionalized PPFS-type polymer results from the grafting of a single mercapto-alcohol at the level of the PPFS-type polymer.

[0112] In a particular embodiment, the comb polymer obtained according to the invention is of formula (III): in which e and q are as defined previously; g corresponds to the average number of functionalized monomeric units; m corresponds to the average number of non-functionalized monomeric units; with g / g+m representing the molar grafting rate, being in particular between 0.01 and 0.35, more particularly between 0.10 and 0.30; the order of succession of the two types of monomeric units forming the polymer of formula (III) being completely random. (iii) Obtaining the comb polymer

[0113] As mentioned above, the process of the invention comprises in step (iii) the formation of polycarbonate / polyester chains directly at the level of the PPFS type polymer, by polymerization from cyclic monomers with five to eight members chosen from lactones and cyclic carbonates.

[0114] More specifically, the pendant hydroxyl functions of the functionalized PPFS type polymer at the end of step (ii) make it possible to initiate the polymerization by ring opening of the monomers.

[0115] The cyclic monomer(s) from which the side chains of the comb polymer are formed correspond more particularly to the following formula (M2): in which: X represents a carbon atom or an oxygen atom; n 1 is 0 or is an integer between 1 and 3; said monomers being optionally substituted, on one or more of the carbon atoms of the cycle, by one or more substituents R 1 . The substituents of the cyclic monomer, R 1 , may be more particularly chosen from alkyl groups, in particular C 1 to C 5 , linear or branched.

[0116] According to a particular embodiment, the side chains formed in step (iii) are polycarbonates, in other words are obtained by polymerization from monomers of the cyclic carbonate type with five to eight members.

[0117] Cyclic carbonates can more particularly be of the following formula (M3): in which m being an integer between 1 and 3, preferably m is 1 or 2, more preferably m is 2; x is 0 or is an integer between 1 and 2m+2; and R 1 , carried by one or more carbon atoms of the cycle, represent, independently of one another, substituents, in particular alkyl groups, in particular C 1 to C 5 , linear or branched.

[0118] Preferably, x is 0.

[0119] Examples of cyclic carbonate monomers include trimethylene carbonate and its derivatives, particularly trimethylene carbonate.

[0120] According to another particular embodiment, the side chains formed in step (iii) are polyesters, in other words are obtained by polymerization from lactone-type monomers.

[0121] By lactone, we mean more particularly monomers corresponding to the following formula (M4): in which n is an integer ranging from 1 to 3, in particular n is 2; y is 0 or is an integer between 1 and 2n+6; and R 1 , carried by one or more carbon atoms of the cycle, represent, independently of each other, substituents, in particular alkyl groups, in particular C 1 to C 5 , linear or branched. In particular, y is 0.

[0122] An example of a lactone monomer is ε-caprolactone.

[0123] As previously mentioned, the side polymer chains formed in step (iii) can be homopolymer or copolymer type chains.

[0124] Preferably, the side polymer chains, preferably of homopolymer type, are formed from one or more cyclic monomer(s) chosen from trimethylene carbonate and ε-caprolactone.

[0125] In particular, the side chains formed in step (iii) may be poly(trimethylene carbonate) (PTMC) chains or poly(ε-caprolactone) (PCL) chains.

[0126] The synthesis of polyesters or polycarbonates by ring-opening polymerization (ROP) under the action of a catalyst and an initiator comprising a hydroxyl function is well known. More particularly, ROP by the cationic route (

[12] -

[14] ) of PCL or PTMC has been proposed, for example by Makiguchi

[14] who uses, as organocatalyst, diphenyl phosphate (DPP) and a phenyl propanol type initiator and allows access to controlled polymerization, in particular a low polydispersity index (PI) and good control of the molar mass as a function of the initial monomer / initiator molar ratio. Polymerization involves almost exclusively the activated monomer mechanism, in other words, the initiation and propagation of the polymerization operate by reaction between the monomer and a hydroxyl function carried by the initiator or located at the end of the propagating chain.In fact, the nature of the linear chain ends is controlled, one of the ends having a hydroxyl function and the other end is dictated by the nature of the initiator, and therefore, in the case of a phenyl propanol type initiator, has a non-reactive character. 1,1' binaphthyl 2,2' diyl hydrogen phosphate (BNPH) has also been proposed as a catalyst, and has better activity than DPP

[15] .

[0127] In the context of the process according to the invention, it is the PPFS polymer functionalized by the hydroxyl functions which thus serves as a macro-initiator for the formation by ROP of the polycarbonate / polyester chains.

[0128] The polycarbonate / polyester chains of the comb polymer formed in step (iii) are advantageously obtained by ROP of one or more cyclic monomers as described previously, for example trimethylene carbonate or ε-caprolactone, in the presence of the functionalized PPFS type polymer as macro-initiator and a catalyst, preferably an organo-catalyst.

[0129] In particular, the ring-opening polymerization reaction in step (iii) is carried out in the presence of a catalyst, preferably an organic or organocatalyst catalyst, such as, for example, diphenyl phosphate (DPP) or 1,1' binaphthyl 2,2' diyl hydrogen phosphate (BNPH). The catalyst and the functionalized PPFS-type polymer are preferably used in proportions such that the molar ratio of the catalyst to the pendant hydroxyl functions of the functionalized PPFS-type polymer is between 0.5 and 5.

[0130] A person skilled in the art is able to adjust the operating conditions of the ROP reaction. The reaction can be carried out with stirring in a solvent medium, for example in one or more apolar and aprotic solvents.

[0131] Preferably, the ROP reaction is carried out in one or more organic solvents capable of solubilizing said PPFS-type polymer functionalized by the pendant hydroxyl functions and said cyclic monomer(s). For example, the ROP reaction can be carried out in dichloromethane (DCM) or toluene, preferably dichloromethane. Preferably, the concentration of cyclic monomer in said organic solvent(s) is between 10 and 1000 g / L, in particular between 50 and 330 g / L.

[0132] The polymerization can be carried out at a temperature between 10°C and 50°C, in particular between 15°C and 40°C, preferably between 20°C and 30°C, for example at room temperature.

[0133] The polymerization time can be between 1 hour and 75 hours. It can be adapted depending on the nature of the cyclic monomer and the desired molar mass of the polymer chains.

[0134] The synthesized comb polymer can be recovered by precipitation in a solvent such as methanol.

[0135] Advantageously, the process of the invention allows good control of the polymerization of the polycarbonate / polyester side chains, in particular of the molar mass and the polydispersity of the polycarbonate / polyester chains obtained directly at the level of the PPFS type polymer.

[0136] In particular, the molar mass of the side chains obtained can be adjusted by varying the molar ratio between the cyclic monomers and the number of pendant hydroxyl functions, in particular the number of monomeric units of the PPFS-type polymer functionalized by a pendant hydroxyl function. According to a particular embodiment, said cyclic monomer(s) and the functionalized PPFS-type polymer are used in proportions such that the molar ratio of said monomer(s) to the pendant hydroxyl functions of the functionalized PPFS-type polymer is between 10 and 100, preferably between 10 and 25.

[0137] Advantageously, the polymerization of the side chains directly at the level of the functionalized PPFS type polymer makes it possible to vary the length of the grafted polycarbonate / polyester type chains very widely.

[0138] Thus, it is possible according to the method of the invention to form polycarbonate / polyester side chains with a number-average molar mass ranging from 800 g.mol -1< to 10,000 g.mol -1< , in particular from 800 to 5000 g.mol -1< .

[0139] In particular, the polycarbonate / polyester side chains formed in step (iii) of the process of the invention may have a number-average molar mass less than or equal to 2000 g.mol -1< , in particular strictly less than 2000 g.mol -1< , in particular between 800 g.mol -1< and 2000 g.mol -1< and more particularly between 800 g.mol -1< and 1500 g.mol -1< . The number-average molecular mass of the polycarbonate / polyester side chains can be determined by size exclusion chromatography (SEC). It can also be obtained from 1< H NMR analysis.

[0140] Advantageously, the polycarbonate / polyester chains obtained have a low polydispersity index, advantageously strictly less than 1.2, preferably between 1 and 1.1. The polydispersity index, noted IP, is equal to the ratio of the weight-average molar mass Mw to the number-average molar mass Mn. Comb polymer

[0141] At the end of step (iii) of the process of the invention, the PPFS type polymer thus has polycarbonate / polyester chains linked in position para of a portion of the pentafluorophenyl groups via thioether bonds, originating from the functionalization in step (ii) of the PPFS type polymer with said mercapto-alcohol(s). Comb polymer purification

[0142] The comb polymer obtained after the formation in step (iii) of the polycarbonate / polyester side chains can be subjected to one or more subsequent purification steps.

[0143] Advantageously, the purification of the comb polymer according to the invention can be carried out by precipitating the comb polymer solubilized in an organic solvent, in a mixture of a first solvent chosen from methanol, ethanol, diethyl ether and their mixtures and a second solvent chosen from dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) and their mixtures, liquid / solid separation, for example filtration, and drying (evaporation of the solvents).

[0144] In particular, said first solvent and said second solvent are miscible.

[0145] The solubilization solvent of the comb polymer may be, for example, dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) or mixtures thereof, in particular dichloromethane. Preferably, the polymer is precipitated in a mixture of acetone and methanol, the person skilled in the art being able to adjust the acetone / methanol volume ratio. In particular, the acetone / methanol volume ratio may be between 20 / 80 and 90 / 10, more particularly between 40 / 60 and 80 / 20, in particular between 50 / 50 and 70 / 30, or even between 55 / 45 and 65 / 35.

[0146] Surprisingly, as illustrated in examples, the inventors have shown that such a purification protocol advantageously makes it possible to eliminate non-grafted polycarbonate / polyester chains, i.e. chains not linked to the PPFS type polymer.

[0147] In a particular embodiment, the purification can be carried out from the reaction medium obtained at the end of the formation of the side polymer chains, comprising said comb polymer in the solvent(s) used for the polymerization of the polycarbonate / polyester chains, in particular in dichloromethane. In particular, notably in the context of the elimination of ungrafted polycarbonate / polyester chains of low molecular mass, the purification can be carried out from the reaction medium obtained at the end of step (iii), by precipitation of said comb polymer in methanol.In another particularly preferred embodiment, the purification can be carried out from the comb polymer recovered at the end of the formation of the side chains in step (iii), by solubilizing said comb polymer in an organic solvent, for example in dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) or mixtures thereof, in particular dichloromethane, then by precipitation in a mixture of a first solvent chosen from methanol, ethanol, diethyl ether and mixtures thereof and a second solvent chosen from DCM, acetone, THF, MEK, DMF and mixtures thereof, in particular in an acetone / methanol mixture, followed by liquid / solid separation, for example filtration, and drying (evaporation of the solvents).

[0148] Preferably, the purification is carried out from the comb polymer recovered at the end of the formation of the side chains in step (iii), by solubilization of said comb polymer in dichloromethane (DCM), then by precipitation in an acetone / methanol mixture, in particular as described previously, followed by a liquid / solid separation, for example filtration, and drying (evaporation of the solvents). Protection of the hydroxyl chain ends of the comb polymer

[0149] In a particular embodiment, the hydroxyl functions present at the ends of the side polycarbonate / polyester chains of the comb polymer may be in protected (or “capped”) form.

[0150] The process for preparing a comb polymer according to the invention may thus further comprise a step of protecting the hydroxyl functions present at the ends of the side polycarbonate / polyester chains of said comb polymer, by reaction with at least one compound, called a protective agent, in particular as described in the remainder of the text. The protection of the hydroxyl functions may be carried out at the end of the synthesis of the comb polymer, preferably after purification as described above.

[0151] The formation of capped hydroxyl ends (more generally referred to as “end-capped” in English terminology) advantageously makes it possible to increase the electrochemical stability of the solid electrolyte formed from said comb polymer(s), the terminal hydroxyl functions being sensitive to reduction and oxidation, and likely to degrade upon contact with lithium salts.

[0152] A hydroxyl function is more particularly protected by forming a more chemically and electrochemically stable function. For example, the protection of hydroxyl functions can be more particularly carried out by reacting said hydroxyl function at the end of the chain with at least one compound, called a protective agent, chosen from acyl chlorides, for example benzoyl chloride, acetyl chloride, etc.; acid anhydrides, for example acetic anhydride, etc., and isocyanates such as p-toluenesulfonyl isocyanate, etc.

[0153] The protection of the hydroxyl functions can be carried out by directly adding said protective agent(s) to the reaction medium obtained at the end of the synthesis of the comb polymer in step (iii) or subsequently in a purification step as described previously, of the comb polymer.

[0154] A person skilled in the art is able to adjust the operating conditions to achieve protection of the hydroxyl function(s) of the ends of the side chains of the comb polymer according to the invention.

[0155] The invention thus relates to a comb polymer, in particular as obtained at the end of the process of the invention described above, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomeric units of the main chain carrying polymeric side chains, called polycarbonate / polyester chains, formed from at least one cyclic monomer of five to eight members chosen from lactones and cyclic carbonates; said side polymeric chains being grafted in para pentafluorophenyl groups via thioether bonds.

[0156] The characteristics described above in the context of the process for preparing the comb polymer, in particular for the PPFS type polymer forming the main chain of the comb polymer and for the polyester / polycarbonate chains of the comb polymer prepared according to the invention, also apply to the comb polymer according to the invention.

[0157] In particular, the comb polymer according to the invention preferably has a main chain of PPFS type having a number-average molar mass M n greater than or equal to 10,000 g.mol -1< , in particular less than or equal to 1,000,000 g.mol -1< , in particular less than or equal to 600,000 g.mol -1< and more particularly between 40,000 g.mol -1< and 400,000 g.mol -1< , in particular between 50,000 g.mol -1< and 100,000 g.mol -1< .

[0158] The polycarbonate / polyester side chains may have a number-average molar mass ranging from 800 g.mol -1< to 10,000 g.mol -1< , in particular from 800 g.mol -1< to 5,000 g.mol -1< . Advantageously, the number-average molar mass of the polycarbonate / polyester side chains may be less than or equal to 2,000 g.mol -1< , in particular strictly less than 2,000 g.mol -1< , in particular be between 800 g.mol -1< and 2,000 g.mol -1< and more particularly between 800 g.mol -1< and 1,500 g.mol -1< .

[0159] As previously indicated, given their mode of polymerization, the side chains advantageously exhibit low polydispersity. In particular, the polydispersity index, the ratio of the weight-average molar mass Mw to the number-average molar mass Mn, is strictly less than 1.2.

[0160] The molar grafting rate of the polycarbonate / polyester type side chains may be less than or equal to 35%, and in particular greater than or equal to 1%, in particular between 5% and 33% and more particularly between 10% and 30%.

[0161] The polycarbonate / polyester side chains preferably have hydroxyl functions at the chain end, in protected or capped form, resulting from the reaction of said hydroxyl function with a protecting agent, as described previously.

[0162] In a particular embodiment, the monomeric units of the comb polymer according to the invention carrying a side chain, in particular obtained according to the process described previously, can thus be of the following formula (IV): in which e, q, X and n 1 are as defined previously; p represents the number of monomeric units of the side chain (corresponding to the degree of polymerization), in particular p is greater than or equal to 4, in particular between 5 and 500, more particularly between 5 and 100, in particular strictly less than 20, or even between 7 and 15, said hydroxyl function at the end of the chain possibly being in protected form, for example in the -OAc form (Ac representing an acetyl group).

[0163] It is understood that X and n 1 may be identical or different for the p monomeric units of the side chain, the side chain thus being able to be a homopolymer of polycarbonate type, for example a PTMC, a homopolymer of polyester type, for example a poly(caprolactone) or even a copolymer formed from one or more distinct cyclic monomers chosen from lactones and cyclic carbonates. Preferably, X and n 1 are identical for the p monomeric units of the side chain.

[0164] In a particular embodiment, the monomeric units of the comb polymer according to the invention carrying a side chain, in particular obtained according to the process described previously, can thus be of the following formula (IV-a): in which e, q, n 1 and p are as defined previously, said hydroxyl function at the end of the chain possibly being in protected form, for example in the -OAc form.

[0165] In another particular embodiment, the monomeric units of the comb polymer according to the invention carrying a side chain, in particular obtained according to the process described previously, can thus be of the following formula (IV-b): in which e, q, n 1 and p are as defined previously, said hydroxyl function at the end of the chain possibly being in protected form, for example in the -OAc form.

[0166] According to a particular embodiment, the side chains of a comb polymer according to the invention, in particular obtained by the process according to the invention, are poly(trimethylene carbonate) chains, said chains being linked to the main chain of PPFS type via a thioether group and preferably having hydroxyl functions at the chain end in protected form, for example in the -OAc form. According to another particular embodiment, the side chains of a comb polymer according to the invention, in particular obtained by the process according to the invention, are poly(ε-caprolactone) chains, said chains being linked to the main chain of PPFS type via a thioether group and preferably having hydroxyl functions at the chain end in protected form, for example in the -OAc form.

[0167] In a particular embodiment, the comb polymer obtained according to the invention is of formula (V): in which e, p, q, n 1 and X are as defined above; said hydroxyl functions at the ends of the side chains being optionally protected, as described above; g corresponds to the average number of monomeric units carrying polymeric side chains; m corresponds to the average number of ungrafted monomeric units; with g / g+m representing the molar grafting rate in polymeric side chains, being in particular less than or equal to 0.35, in particular between 0.01 and 0.35, for example between 0.05 and 0.35, in particular strictly less than 0.35, more particularly between 0.10 and 0.30; the order of succession of the two types of monomeric units forming the polymer of formula (V) being completely random. PREPARATION OF SOLID ELECTROLYTE

[0168] As mentioned above, the comb polymers according to the invention, in particular obtained by the process according to the invention, preferably after protection of the hydroxyl functions at the ends of the side polycarbonate / polyester chains, can be used, in combination with at least one ionic salt, to form a solid electrolyte, in particular in an electrochemical system, in particular in a lithium battery.

[0169] The solid electrolyte can be a solid polymer electrolyte (also called SPE for “Solid Polymeric Electrolyte” in Anglo-Saxon terminology) or a hybrid solid electrolyte (HSE for “Hybrid Solid Electrolyte” in Anglo-Saxon terminology).

[0170] The electrolyte formed according to the invention may be in any suitable form, in particular in the form of a film or a membrane.

[0171] In particular, the polymer network formed from the comb polymers according to the invention, in particular obtained by the process according to the invention, forms more than 50% by mass, in particular more than 75% by mass, of the total mass of said solid electrolyte.

[0172] Advantageously, the solid polymeric electrolyte film according to the invention is free from plasticizing agents, such as carbonates, for example ethylene carbonate or diethyl carbonate.

[0173] In particular, the solid electrolyte film according to the invention is distinct from a gel-type electrolyte, comprising a majority quantity of plasticizer.

[0174] The preparation of a solid electrolyte from the comb polymers according to the invention more particularly implements at least the following steps: (a) mixing, in the presence or absence of a solvent medium, of at least: one or more comb polymers according to the invention, as described previously, in particular obtained by the process according to the invention, at least one alkali or alkaline-earth metal salt, in particular a lithium salt; and optionally, in particular in the case of the preparation of an HSE, at least one inorganic filler; (b) formation, in particular on the surface of a substrate, of a solid electrolyte from said mixture.

[0175] The alkali or alkaline earth metal salt is used with the comb polymer according to the invention to ensure the conduction of the ions.

[0176] In the context of the invention, the following terms are understood to mean: “alkali metals”, the chemical elements of the first column of the periodic table of elements, and more particularly chosen from lithium, sodium, potassium, rubidium, cesium. Preferably, the alkali metal is lithium, sodium or potassium, and more preferably lithium; “alkaline earth metals”, the chemical elements of the second column of the periodic table of elements, and more particularly chosen from beryllium, magnesium, calcium, strontium, barium, radium. Preferably, the alkaline earth metal is magnesium or calcium.

[0177] The salt of an alkali metal may be, for example, a lithium salt or a sodium salt; the salt of an alkaline earth metal may be, for example, a magnesium salt.

[0178] Examples of lithium salts include LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiCF 3 SO 3 , LiN(C 2 F 5 SO 2 ) 2 , lithium bistrifluoromethylsulfonylimide LiN[SO 2 CF 3 ] 2 (known as LiTFSI), lithium bis(fluorosulfonyl)amide (known as LiFSI) LiN[SO 2 F] 2 , lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (known as LiTDI), lithium bispentafluoroethylsulfonylimide (known as LiBETI), lithium bis(oxalato)borate (known as LiBOB) and lithium difluoro(oxalato)borate (known as abbreviation LiFOB) and mixtures thereof.

[0179] Preferably, the electrolyte comprises, as lithium salt, LiTFSI or LiFSI, preferably LiTFSI.

[0180] It is up to the person skilled in the art to adjust the quantity of alkali or alkaline earth metal salts, in particular with regard to the nature of the comb polymer, and in particular the nature of the side polycarbonate / polyester chains carried by the comb polymer, used according to the invention.

[0181] According to a particular embodiment, the quantities of comb polymer(s) and lithium salt(s) are adjusted so that the molar ratio between the carbonyl groups of the polycarbonate / polyester side chains (in other words CO 3 groups in the case of polycarbonate chains, and CO 2 groups in the case of polyester chains) relative to the lithium, noted [CO] / [Li +< ], is between 0.1 and 30, in particular between 0.5 and 20 and more particularly between 5 and 15.

[0182] According to a first embodiment variant, said comb polymer(s) according to the invention are used to form a solid polymer electrolyte (SPE), the preparation of said electrolyte comprising the mixture of at least one comb polymer according to the invention and of which the terminal hydroxyl functions are optionally protected, and at least one alkali or alkaline-earth metal salt, for example a lithium salt.

[0183] According to another embodiment variant, said comb polymer(s) according to the invention are used to form a hybrid solid electrolyte (HSE), the preparation of said electrolyte then comprising the mixture of at least one comb polymer according to the invention and whose terminal hydroxyl functions are protected, of at least one alkali or alkaline-earth metal salt, for example a lithium salt and, in addition, of at least one inorganic filler.

[0184] The inorganic fillers may be chosen from inorganic fillers which conduct alkali or alkaline-earth cation(s), in particular which conduct lithium ions, non-conductive fillers which conduct alkali or alkaline-earth cation(s), and mixtures thereof.

[0185] The lithium ion conductive fillers can be chosen, for example, from lithiated oxides, such as Li 7 La 3 Zr 2 O 12 (LLZO) and Li 0.33 La 0.56 TiO 3 (LLTO), Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), etc.

[0186] These may also be charges chosen from: garnets, for example chosen from Li 7 La 3 Zr 2 O 12 , Li 6 La 2 BaTa 2 O 12 , etc.; lithiated phosphates, for example chosen from Li 3 PO 4 , LiPO 3 , etc.; lithiated borates, for example chosen from Li 3 BO 3 , etc.; oxynitrides, for example chosen from Li 3 PO 4-x N 2x / 3 , Li 4 SiO 4-x N 2x / 3 , Li 4 GeO 4-x N 2x / 3 with 0 <x<4 ou Li 3 BO 3-x N 2x / 3 avec 0<x<3 ; les composés lithiés à base d'oxynitrure de lithium et de phosphore (appelés LiPON) ; les silicates, par exemple Li 2 Si 2 O 5 ; les sulfurés, par exemple l'argyrodite.

[0187] Non-conductive fillers of alkali or alkaline-earth cations can for example be chosen from alumina (Al 2 O 3 ), silica (SiO 2 ), titanium dioxide (TiO 2 ) etc.

[0188] Said inorganic filler(s) may be used in a filler(s) / polymer(s) comb volume ratio of between 1 / 99 and 80 / 20, in particular between 20 / 80 and 80 / 20, more particularly between 20 / 80 and 60 / 40.

[0189] The mixing of said comb polymer(s) according to the invention, said alkali or alkaline-earth metal salt(s) and, optionally, said inorganic filler(s), is more particularly carried out under conditions allowing good dispersion of said alkali or alkaline-earth metal salt(s) and, optionally, of said inorganic filler(s), at the level of the comb polymers according to the invention. The mixing can be carried out in the presence or absence of a solvent.

[0190] The preparation of a solid electrolyte film according to the invention can thus be carried out either by the route using a solvent medium (called "solvent route"), or by the route using the polymer in the molten state, in the absence of solvent (called "dry route" or "molten route"). According to a first embodiment variant, the solid electrolyte film is prepared by the "solvent" route. In the context of this variant, the mixture of said comb polymer(s) according to the invention, of said alkali or alkaline-earth metal salt(s) and, optionally, of said inorganic filler(s), is more particularly carried out in a solvent medium. The solvent medium can be formed from one or more polar organic solvents. By way of examples, they can be chosen from acetone, tetrahydrofuran (THF), acetonitrile and mixtures thereof.

[0191] Preferably, the mixture is heated to a temperature below 100°C. In particular, the mixture is carried out at a temperature greater than or equal to 25°C, in particular between 40 and 60°C.

[0192] The solid electrolyte may be formed by depositing said mixture on the surface of a substrate, for example by coating, followed by evaporation of said solvent(s), in particular to obtain a “dry” electrolyte or film.

[0193] In particular, said solvent(s) may be evaporated under vacuum at a temperature of between 70°C and 90°C, in particular approximately 80°C.

[0194] By "dry" is meant that the solid electrolyte or solid electrolyte film comprises less than 0.1% by mass of solvent, in particular less than 0.05% by mass and more particularly less than 0.02% by mass of solvent.

[0195] According to another embodiment, the solid electrolyte, in particular in the form of a film, is prepared in the absence of solvent, by the “melt” route, in particular by extrusion.

[0196] In the context of this embodiment variant, the molten mixture may more particularly be carried out by heating to a temperature greater than Tg + 30°C, where Tg is the glass transition temperature of the comb polymer. In particular, the mixture is carried out at a temperature greater than or equal to 0°C, in particular between 20°C and 80°C.

[0197] The molten mixture can then be formed into a film, supported by a substrate or self-supported, by any melt extrusion technique known to those skilled in the art.

[0198] As mentioned above, the solid electrolyte can be prepared in the form of an electrolyte film or membrane directly on the surface of a suitable substrate, in particular an inert one.

[0199] The substrate can be of various types. It can be made of glass, alumina, silicone, polyimide, polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), silicone, polypropylene or even stainless steel.

[0200] The solid electrolyte film can optionally be detached from the substrate to be implemented at the level of the electrochemical system for which it is intended, in particular transferred onto at least one electrode.

[0201] The solid electrolyte film may have, for example, a thickness of between 20 and 500 µm, in particular between 20 and 100 µm and more particularly between 40 and 60 µm. ELECTROCHEMICAL SYSTEM

[0202] The solid electrolyte obtained according to the invention, in particular of the SPE or HSE type, can be advantageously used as a solid electrolyte in an electrochemical system. The invention also relates, according to another of its aspects, to an electrochemical system comprising a solid electrolyte, in particular a solid electrolyte film according to the invention, in particular acting both as an ionic conductor and as a separator between the positive and negative electrodes.

[0203] The electrochemical system may be a generator, converter or electrochemical storage system. More specifically, it may be a fuel cell, for example a primary or secondary battery, for example a lithium, sodium, magnesium, potassium or calcium battery; a flow battery ("redox flow battery" in English terminology); a lithium-air or lithium-sulfur accumulator.

[0204] According to a particular embodiment, the solid electrolyte is implemented in a rechargeable battery, in particular in a lithium battery, in particular a lithium-ion or lithium-metal battery.

[0205] The solid electrolyte according to the invention can be more particularly implemented as a separator electrolyte within an electrochemical system. The term "separator electrolyte" means a film of solid electrolyte positioned between the positive and negative electrodes of an electrochemical system, and acting both as an ionic conductor and separator between the positive and negative electrodes.

[0206] In particular, the invention also relates, according to another of its aspects, to an electrode / electrolytic membrane assembly, comprising a solid electrolyte membrane according to the invention.

[0207] An electrochemical system according to the invention generally comprises at least one positive electrode and one negative electrode between which there is a solid electrolyte film acting both as an ionic conductor and separator between the positive and negative electrodes.

[0208] The positive electrode of a lithium battery generally comprises, as electrochemically active material, lamellar compounds, such as LiCoO 2 , LiNiO 2 and mixed Li(Ni, Co, Mn, Al)O 2 , or compounds of spinel structure of compositions close to LiMn 2 O 4 , lithium phosphates, in particular LiMnFePO 4 or LiFePO 4 .

[0209] Advantageously, the positive electrode comprises, as electrochemically active material, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 (NCM cathodes) or LiCoO 2 , preferably LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 .

[0210] The negative electrode generally comprises, as electrochemically active material, lithium metal or lithium-based alloy in the case of primary accumulators, or intercalation materials such as graphite carbon, or lithiated titanium oxide (Li 4 Ti 5 O 12 ) or titanium and niobium oxide (TiNb 2 O 7 ), in the case of accumulators based on lithium-ion technology.

[0211] Advantageously, it may be a lithium-metal battery, comprising a lithium metal electrode Li 0 < and an electrode comprising LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 or LiCoO 2 , preferably LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 .

[0212] The invention will now be described by means of the following examples and figures, given of course for illustrative purposes and not as a limitation of the invention. Example 1 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) intended to form the main chain of a comb polymer according to the invention 1.1 Synthesis of a PPFS by bulk polymerization under Ziegler Natta catalysis ("PPFS- 03") Preparation of a Ziegler Natta catalyst solution:

[0213] In a glove box, 1.2 mL of TiCl 4 (1 equivalent) and 15 mL of anhydrous toluene are added to a 100 mL two-necked flask topped with a dropping funnel. 1.9 mL of AlEt 3 (1.2 equivalents) and 15 mL of toluene are added to the addition funnel. The assembly is removed from the glove box and the bottom of the two-necked flask is immersed in an ice bath; the AlEt 3 solution is added dropwise to the TiCl 4 solution while stirring vigorously. The ice bath is removed at the end of the addition and the reaction mixture is kept stirring for 30 min at room temperature. The Ziegler Natta catalyst solution is ready for use. Polymerization of PPFS:

[0214]

[0215] 75 mL of 2,3,4,5,6-pentafluorostyrene (PFS; 50 equivalents) are introduced into a 500 mL two-necked flask. The assembly is placed under argon flow. 25 mL of Ziegler Natta catalyst solution are added to the two-necked flask. The reaction medium is stirred and heated at 70°C for 4 h, then at 120°C for 36 h. At the end of polymerization, a black solid is obtained at the bottom of the flask.

[0216] The solid is solubilized in fluorobenzene and then the synthesized poly(2,3,4,5,6-pentafluorostyrene) (PPFS) is purified by precipitation in MeOH. After filtration, the PPFS (white powder) is dried under vacuum at 60°C for 48 hours.

[0217] 69.8 g of PPFS, named "PPFS-03", are obtained with a mass yield of approximately 93%.

[0218] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H and 19< F ( Figure 1 ): NMR 19< F (400 MHz; CDCl 3; 298 K): δ ppm: -143ppm (m, 2F orto ) ; -154ppm (s, 1F para ) ; -161ppm (s, meta ).

[0219] The number-average molar mass Mn determined by Size Exclusion Chromatography (CES (THF, 30°C, TDS calibration)) ( Figure 2 ) is 53 kg / mol with a polydispersity index, IP = M w / M n , of 2.2. 1.2 Synthesis of a PPFS by radical emulsion polymerization ("PPFS-Em-01")

[0220]

[0221] 30 mL of distilled water and 0.3 g of SDS (sodium dodecyl sulfate, 2% by mass of PFS) are introduced into a mini-reactor. The medium is stirred and heated to 75°C for 30 min. 15 g of PFS are introduced into the reactor. 15 min after the addition, 0.17 g of ammonium persulfate (1.1% by mass of PFS), dissolved in 15 mL of distilled water, are added to the mini-reactor. The medium is kept stirring and heated to 75°C for 3 h and then to 85°C for 1 h. A white latex is obtained.

[0222] The latex is precipitated in ethanol and then filtered. The product is dried at 60°C under vacuum for 48 hours. 10.8 g of PPFS, named PPFS-Em-01, are obtained with a mass yield of approximately 72%.

[0223] The number-average molar mass Mn determined by CES (THF, 30°C, TDS calibration) ( Figure 3 ) is 280 kg / mol with a polydispersity index, IP = M w / M n , of 1.9.

[0224] The polymer is also characterized by nuclear magnetic resonance (NMR) of 1< H and 19< F ( Figure 4 ). Example 2 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) functionalized by a mercapto-alcohol

[0225] 2.1. Functionalization of "PPFS-03" synthesized in Example 1.1 by 6-mercaptohexan-1-ol ("PPFS-gS-OH-01") - grafting rate of 20%

[0226] In a 100 mL two-necked flask, 6.2 g of "PPFS-03" synthesized in Example 1.1 (1 equivalent) are solubilized in 62 mL of MEK while stirring at room temperature. After solubilization, 1.1 mL of 6-mercaptohexan-1-ol (0.25 equivalent) are added to the flask. After 5 min of stirring, 0.5 mL of DBU (0.1 equivalent) are introduced into the reaction medium. The reaction medium is stirred for 6 h at room temperature.

[0227] After the reaction time, the reaction medium is directly precipitated in cold MeOH. The precipitate is filtered. A white solid powder is obtained.

[0228] The molar grafting rate, also called substitution rate, in 6-mercaptohexan-1-ol on the repeating units of PPFS is estimated by 19< F NMR ( Figure 5 ) at 20%.

[0229] The product is called "PPFS-gS-OH-01" or "PPFS-g 0.2 -S-OH". 2.2. Functionalization of "PPFS-03" synthesized in example 1.1 by 6-mercaptohexan-1-ol ("PPFS-gS-OH-02") - grafting rate 35%

[0230] In a 50 mL two-necked flask, 1 g of "PPFS-03" synthesized in Example 1.1 (1 equivalent) is solubilized in 10 mL of MEK while stirring at room temperature. After solubilization, 285 µL of 6-mercaptohexan-1-ol (0.4 equivalent) are added to the flask. After 5 min of stirring, 162 µL of DBU (0.2 equivalent) are introduced into the reaction medium. The reaction medium is stirred for 6 h at room temperature.

[0231] After the reaction time, the reaction medium is directly precipitated into cold MeOH. The precipitate is filtered. A white solid product is obtained.

[0232] The molar grafting rate, also called substitution rate, in 6-mercaptohexan-1-ol on the repeating units of PPFS is estimated by 19< F NMR ( Figure 6 ) at 35%.

[0233] The product is called "PPFS-gS-OH-02" or "PPFS-g 0.35 -S-OH". Example 3 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) comb polymer carrying poly(trimethylene carbonate) grafts (PPFS-gS-PTMC)

[0234] 3.1. Synthesis of a comb polymer PPFS-g 0.2 -S-PTMC 1000 -OH ("PPFS-gS-PTMC-OH-

[0235] 1 g of "PPFS-gS-OH-01" synthesized in Example 2.1 (1 equivalent) and 1.41 g of TMC (15 equivalents) are introduced into a 50 mL two-necked flask. The assembly is placed under argon flow. 15 mL of DCM are added to the flask in order to solubilize the functionalized PPFS and the TMC. After solubilization, 0.29 g of DPP (1.25 equivalents) are added to the flask. The reaction medium is kept stirring for 48 hours.

[0236] After the reaction time, the reaction medium is directly precipitated in cold MeOH. The product obtained, in the form of a transparent viscous polymer, is solubilized in DCM and precipitated in an acetone / MeOH mixture in order to remove the PTMC chains not grafted to the PPFS. The product thus purified is named "PPFS-gS-PTMC-OH-03".

[0237] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H (CDCl 3 , 298K, 400MHz) ( Figure 7) and by CES (THF, 30°C, TDS calibration) ( figure 8 ). The elimination of the majority of non-grafted PTMC chains on the PPFS is confirmed by CES as represented in figure 8 .

[0238] The number-average molar mass of PTMC chains is estimated by 1< H NMR at 1000 g / mol. 3.2. Synthesis of a comb polymer PPFS-g 0.2 -S-PTMC 800 -OH ("PPFS-gS-PTMC-OH-04")

[0239] 0.5 g of "PPFS-gS-OH-01" synthesized in Example 2.1 (1 equivalent) and 0.7 g of TMC (15 equivalents) are introduced into a 50 mL two-necked flask. The assembly is placed under argon flow. 7 mL of DCM are added to the flask in order to solubilize the functionalized PPFS and the TMC. After solubilization, 0.1 g of DPP (1 equivalent) are added to the flask. The reaction medium is kept stirring for 20 h at room temperature.

[0240] After the reaction time, the reaction medium is directly precipitated in cold MeOH. After drying, the product, in transparent viscous form, is obtained. It is named "PPFS-gS-PTMC-OH-04".

[0241] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H (CDCl 3 , 298K, 400MHz) ( Figure 9 ) and by CES (THF, 30°C, TDS calibration) ( Figure 10 ). The elimination of non-grafted PTMC chains on the PPFS is confirmed by CES.

[0242] The number-average molar mass of PTMC chains is estimated by 1< H NMR at 800 g / mol. Example 4 Preparation of electrolytes and electrochemical properties

[0243] The comb polymer "PPFS-gS-PTMC-OH-03", synthesized in Example 3.1 (762 mg) is mixed with lithium salt LiTFSI (112.5 mg) in THF at 56°C.

[0244] After evaporation of the solvent, the electrolyte is dried under vacuum at 80°C. The solid electrolyte is then incorporated into a symmetrical wedge (stainless steel) / electrolyte / wedge (stainless steel) button cell for the determination of its ionic conductivity by EIS (Electrochemical Impedance Spectroscopy).

[0245] A solid electrolyte is also prepared and incorporated into a button cell according to a protocol similar to that described previously, based on the comb polymer "PPFS-gS-PTMC-OH-04" synthesized in example 3.2.

[0246] In these electrolytes, the amounts of comb polymers and lithium salt are adjusted so that the CO 3 / Li molar ratio is 15.

[0247] There Figure 11 represents the evolution of the ionic conductivity of the polymer electrolytes formed as a function of temperature and demonstrates good ionic conductivity. List of cited documents

[0248] [1] Mindemark et al., Progress in Polymer Science, 81:114-43 (2018). [2] Bocharova et al., Macromolecules, 53:4141-57 (2020). [3] Bouchet et al., Innovations technologiques (2015). [4] Li et al., Progress in Polymer Science, 122:101453 (2021). [5] EP 3 865 533 A1. [6] EP 3 865 532 A1. [7] Atanasov et al., Solid State Ionics, 9 (2013). [8] Hiorns et al.. Polymer, 43:3365-9 (2002). [9] EP 3 763 748 A1.

[10] Yin, Thiol-para-fluoro modified PPFS as building blocks for the design of silica-based nanocomposite and layer by layer self-assembled thin films (2018).

[11] Yin, European Polymer Journal, 10 (2018).

[12] Fukushima, Chapter 7, Polymer Chemistry Series, Cambridge: Royal Society of Chemistry (2018).

[13] Makiguchi et al, Macromolecules, 44:1999-2005 (2011).

[14] Makiguchi et al., Macromolecules, 46:1772-82 (2013).

[15] Liu et al.. Polym Chem, 7:5526-35 (2016).

Claims

1. Process for preparing a comb polymer comprising at least the steps consisting in: (i) providing a polymer formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, referred to as "PPFS-type polymer", which is intended to form the main chain of the comb polymer; (ii) functionalizing a portion of the pentafluorophenyl groups of the monomer units of the PPFS-type polymer with pendent hydroxyl functions, by reacting said PPFS-type polymer with at least one molecule, referred to as "mercapto alcohol", comprising one or more free hydroxyl functions, preferably just one free hydroxyl function, and a free thiol function, said functionalization involving a nucleophilic substitution reaction between the fluorine atom in the para position of the pentafluorophenyl group and the thiol function borne by said mercapto alcohol; and (iii) forming side chains of polyester / polycarbonate type on the functionalized PPFS polymer obtained in step (ii), by ring-opening polymerization proceeding from at least one five- to eight-membered cyclic monomer chosen from lactones and cyclic carbonates.

2. Process according to the preceding claim, wherein said nucleophilic substitution reaction in step (ii) for functionalizing said PPFS-type polymer with pendent hydroxyl functions is performed in the presence of an aprotic base that is weaker than sodium hydride, sodium hydroxide and potassium hydroxide, preferably an aprotic base having a pKa of strictly less than 15 and strictly greater than 10, in particular strictly less than 14, more particularly less than or equal to 13, or even of between 10.2 and 13, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or triethylamine (TEA).

3. Process according to Claim 1 or 2, wherein said PPFS-type polymer is a poly(2,3,4,5,6-pentafluorostyrene).

4. Process according to any one of the preceding claims, wherein said PPFS-type polymer has a number-average molar mass Mn, determined by size exclusion chromatography, of greater than or equal to 10 000 g.mol-1, in particular of between 10 000 g.mol-1 and 1 000 000 g.mol-1, in particular between 40 000 g.mol-1 and 600 000 g.mol-1, more particularly of between 40 000 g.mol-1 and 400 000 g.mol-1.

5. Process according to any one of the preceding claims, wherein the functionalization in step (ii) employs one or more mercapto alcohols comprising just one free hydroxyl function, in particular chosen from mercapto alkanols, more particularly chosen from 4-mercaptobutan-1-ol, 5-mercaptopentan-1-ol, 6-mercaptohexan-1-ol and 7-mercaptoheptan-1-ol, preferably 6-mercaptohexan-1-ol.

6. Process according to any one of the preceding claims, wherein said mercapto alcohol(s) according to the invention and said PPFS-type polymer are employed in a mercapto alcohol(s) / monomer units of the PPFS-type polymer molar ratio of between 0.05 and 0.5, in particular between 0.1 and 0.5.

7. Process according to any one of the preceding claims, wherein the polymeric side chains, preferably of homopolymer type, are formed from one or more cyclic monomers chosen from trimethylene carbonate and ε-caprolactone.

8. Process according to any one of the preceding claims, wherein the ring-opening polymerization reaction in step (iii) is performed in the presence of a catalyst, in particular an organic catalyst, preferably chosen from diphenyl phosphate (DPP) and 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BNPH).

9. Process according to any one of the preceding claims, further comprising at least one step of purifying the comb polymer, said purification step being performed using the reaction medium obtained at the end of step (iii) by precipitating the comb polymer in methanol; or by dissolving the comb polymer recovered at the end of step (iii) in an organic solvent, for example in dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), or mixtures thereof, in particular DCM, and then by precipitating the comb polymer in a mixture of a first solvent chosen from methanol, ethanol, diethyl ether, and mixtures thereof, and of a second solvent chosen from DCM, acetone, THF, MEK, DMF, and mixtures thereof, in particular in an acetone / methanol mixture, followed by liquid / solid separation, for example filtration, and drying.

10. Process according to any one of the preceding claims, further comprising a step of protecting the hydroxyl functions present at the ends of the polycarbonate / polyester side chains of said comb polymer, by reaction with at least one compound, referred to as protecting agent, chosen from acyl chlorides, acid anhydrides and isocyanates.

11. Comb polymer, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomer units of the main chain bearing polymeric side chains, referred to as polycarbonate / polyester chains, formed from at least one five- to eight-membered cyclic monomer chosen from lactones and cyclic carbonates; said polymeric side chains being grafted in the para position of the pentafluorophenyl groups via thioether bonds.

12. Comb polymer according to the preceding claim, said polymer being obtained by the process defined according to any one of Claims 1 to 10.

13. Comb polymer according to Claim 11 or 12, wherein said polycarbonate / polyester chains have a number-average molar mass, determined for example by 1H NMR analysis, of between 800 g.mol-1 and 10 000 g.mol-1, in particular between 800 g.mol-1 and 5000 g.mol-1, more particularly of less than or equal to 2000 g.mol-1, especially of between 800 g.mol-1 and 2000 g.mol-1, or even between 800 g.mol-1 and 1500 g.mol-1.

14. Comb polymer according to any one of Claims 11 to 13, having a molar degree of grafting of side chains, determined by 19F fluorine nuclear magnetic resonance (NMR), of less than or equal to 35%, in particular of between 1% and 35%, more particularly between 10% and 30%.

15. Solid electrolyte, in particular of solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type, comprising, or even being formed of: - at least one comb polymer as obtained according to the process of any one of Claims 1 to 10 or as defined according to any one of Claims 11 to 14, of which the hydroxyl functions at the ends of the grafted side chains are preferably protected; - at least one alkali or alkaline earth metal salt, in particular a lithium salt; and - optionally one or more inorganic fillers.

16. Electrochemical system, in particular an energy storage device, especially a rechargeable battery, in particular a lithium battery, comprising a solid electrolyte, in particular a film of solid electrolyte, as defined in Claim 15.