Process for the preparation and purification of a polymer comprising disulfide bridges

Abstract

The present invention relates to a process for the preparation and purification of a polymer comprising disulfide bridges.

Description

Title of the invention: Process for preparing and purifying a polymer comprising disulfide bridges. Technical field of the invention

[0001] The present invention relates to the preparation and purification of polymers comprising disulfide bridges. More particularly, the present invention relates to the preparation and purification of poly(1,8-dimercapto-3,6-dioxaoctane). Technological background of the invention

[0002] The next-generation lithium-ion secondary battery aims to use a solid electrolyte instead of a liquid electrolyte. This allows for higher energy density and improved safety compared to traditional lithium-ion batteries. All-solid-state batteries are also more resistant to thermal runaway, a major concern with traditional lithium-ion batteries. They have the potential to enable further miniaturization and integration of electronic devices, as well as improve the range and safety of electric vehicles. However, the commercialization of solid-state batteries is still in its early stages, and technical challenges remain before they can be widely adopted.

[0003] Solid polymer electrolytes have been investigated as alternative electrolytes for Li-ion batteries due to their good mechanical strength, high ionic conductivity, and safety advantages. They consist of a polymer matrix containing conductive salts of Li ions. The polymers form a flexible and stable membrane that can separate the cathode and anode of the battery, while allowing the Li-ions to move freely through the electrolyte. This can improve battery performance and stability, but some challenges remain, such as a low Li-ion transfer number and a limited operating temperature range.

[0004] One of the most widely used polymers is polyethylene oxide (PEO). Due to the crystalline nature of PEO (Tm between 60 and 70 °C), it suffers from low ionic conductivity at room temperature. Therefore, it is primarily used at high temperatures to increase conductivity (in molten form). Operating temperatures are significantly impacted and limited to high-temperature applications. However, an all-solid-state battery may be necessary in countries with low winter temperatures and requires conductivity even below 0 °C. There is therefore a continued need to develop new all-solid-state batteries incorporating new polymers. Sulfur-containing or disulfide-bonded polymers are considered. However, the preparation of this type of polymer can be complex. For the intended applications, it is important to control the molecular weight of the polymers while limiting the presence of impurities. The present invention makes it possible to solve, at least in part, the problems identified above by providing a process for preparing a polymer suitable for use in novel all-solid-state battery applications. Summary of the invention

[0005] According to a first aspect, the present invention relates to a process for preparing a PI polymer comprising at least one disulfide bond, said process comprising: a. A polymerization step, preferably in aqueous medium, by adding a solution of a peroxide to a dispersion, preferably aqueous, comprising at least one compound of formula (I) HS-R-SH and a base for forming said polymer PI comprising at least one -(SRS)-(SRS)- segment with R being, independently for each -(SRS)- unit, a hydrocarbon substituent having a molecular mass less than 1000 g / mol.

[0006] According to a preferred embodiment, said PI polymer has a weight average molecular mass Mw, expressed in kg / mol, between: ((2226 + 1951754*C1)*0.00055) < Mw < ((2226 + 1951754*C1)*0.00145); Cl being the concentration of said peroxide solution, expressed in % by weight.

[0007] According to a preferred embodiment, said process includes a step b) of purifying said PI polymer obtained in step a) comprising a step of removing said base used in step a) or a step of filtering said PI polymer or a combination of both.

[0008] According to a preferred embodiment, said step of removing said base used in step a) is carried out by heat treatment of said PI polymer at a temperature of 20°C to 100°C and a pressure of 0.01 bara to 1 bara, prior to and / or after said filtration of said PI polymer.

[0009] According to a preferred embodiment, said filtration step of said PI polymer is carried out using a filtration device comprising a membrane made of at least one fluorinated polymer or a polyolefin.

[0010] According to a preferred embodiment, said membrane comprises pores of a size from 1 nm to 100 nm, advantageously from 1 nm to 75 nm, preferably from 2 nm to 50 nm, more preferably from 3 nm to 25 nm, in particular from 3 nm to 10 nm.

[0011] According to a preferred embodiment, said base used in step a) has a saturated vapor pressure greater than IkPa at 20°C.

[0012] According to a preferred embodiment, said peroxide used in step a) is selected from the group consisting of organic peroxides, percarbonates, perborates, persulfates, perphosphates and hydroperoxides.

[0013] According to a preferred embodiment, said compound of formula (I) is HS-R-SH in which R is a hydrocarbon comprising at least one ether, ester or carbonyl functional group.

[0014] According to a preferred embodiment, R has the formula -[R'-X-]n-[Y]m- in which

[0015] R1 is, independently for each unit n, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0016] X is O, C(O), C(O)O, OC(O);

[0017] n is an integer from 1 to 20;

[0018] Y is, independently for each unit m, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0019] m is an integer from 0 to 20.

[0020] According to a preferred embodiment, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl.

[0021] According to a preferred embodiment, said compound of formula (I) is 1,8-dimercapto-3,6-dioxaoctane and in that said polymer PI is poly(1,8-dimercapto-3,6-dioxaoctane).

[0022] According to a preferred embodiment, said base is selected from the group consisting of LiOH, NaOH, KOH, CsOH, RbOH, Mg(OH)2, Ca(OH)2, NHx(CnH2n+1)3 x with n being an integer from 1 to 10 and x an integer from 0 to 3, N,N-Diisopropylethylamine, morpholine, pyridine, pyrrolidine, Piperidine, piperazine, 4-Methylmorpholine, 1,8-Diazabicyclo(5.4.0)undec-7-ene, 6-(Dibutylamino)-1,8-diazabicyclo[5.4.0]undec-7-ene, 1,8-Diazabicyclo[5.4.0]undec-7-ene bonded to polystyrene, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene, 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-Tetramethylguanidine, 2-tert-Butyl-1,1,3,3-tetramethylguanidine, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene linked to polystyrene, 1,4-Diazabicyclo[2.2.2]octane, Quinuclidine, 1,5-Diazabicyclo(4.3.0)non-5-ene, 2,6-Di-tert-butylpyridine, 2,8,9-Trimethyl-2,5,8,9-tetraza-1-phosphabicyclo[3.3.3]undecane, Cyclodiphosphazane, Lithium diisopropylamide, sodium diisopropylamide, potassium diisopropylamide, magnésium diisopropylamide, calcium diisopropylamide, rubidium diisopropylamide, lithium bis(trimethylsilyl) amide, sodium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, magnésium bis(trimethylsilyl)amide, calcium bis(trimethylsilyl)amide, rubidium bis(trimethylsilyl)amide, lithium tetramethylpiperidide, sodium tetramethylpiperidi de, potassium tetramethylpiperidide, magnésium tetramethylpiperidide, calcium . tetramethylpiperidide, rubidium tetramethylpiperidide, [18-crown-6]-KHF2, KHF2, N,N’-diisopropylimidazonium, bifluorure, tetrabutylammonium, N(CnH2n+i)4+OH avec n étant un entier de 1 à 10.

[0023] According to another aspect, the present invention provides a composition comprising at least 99.5% by mole of said PI polymer as defined according to the present invention; said PI polymer having a weight average molecular mass Mw greater than 10000 g / mol, preferably greater than 15000 g / mol, in particular greater than 20000 g / mol.

[0024] According to a preferred embodiment, said composition comprises: - from 1 ppb to 100 ppm in mole of sodium; - less than 10 ppm by mole of a metal selected from the group consisting made of iron, aluminum, copper and magnesium;

[0025] based on said total composition.

[0026] According to a preferred embodiment, said composition comprises less than 0.5% by mole of said base as defined in the present invention on the basis of the total composition.

[0027] According to a preferred embodiment, said composition comprises less than 0.1% by mole of water on the basis of the total composition.

[0028] According to another aspect, the present invention provides a film comprising the composition according to the present invention.

[0029] According to another aspect, the present invention provides an electrochemical device comprising said film according to the present invention.

[0030] According to another aspect, the present invention provides poly(l,8-dimercapto-3,6-dioxaoctane) having a weight average molecular mass Mw greater than 10000 g / mol, and comprising less than 0.1% by weight of water. Brief description of the figures

[0031] Fig. 1 represents the cyclic voltammetry of a film prepared with a polymer according to an embodiment of the present invention. Detailed description of the invention

[0032] The present invention provides a method for preparing a disulfide polymer. The present invention makes it possible to prepare this type of polymer by effectively controlling the molecular mass obtained. Controlling the molecular mass of the polymer is very useful for the intended applications. By controlling it, different properties can be obtained in the conductivity of a film containing the polymer. Preparation process

[0033] Said process for preparing the PI polymer comprises a) a polymerization step, preferably in aqueous medium, by adding a solution of a peroxide on a dispersion, preferably aqueous, comprising at least one compound of formula (I) HS-R-SH and a base for forming said polymer PI comprising at least one -(SRS)-(SRS)- segment with R being, independently for each -(SRS)- unit, a hydrocarbon substituent having a molecular mass less than 1000 g / mol.

[0034] Step a)

[0035] Said step a) is preferably carried out in such a way as to control the temperature of the reaction medium. The reaction between the peroxide and the compound of formula (I) in the presence of said base is exothermic. The temperature of the reaction medium is preferably controlled to maintain efficient polymerization. For example, the rate of addition of said peroxide solution is thus adapted to maintain the temperature between 10°C and 50°C, advantageously between 15°C and 45°C, preferably between 15°C and 40°C, in particular between 15°C and 35°C.

[0036] Said step a) can be carried out under an inert or non-inert atmosphere. Thus, said step a) can be carried out under an atmosphere of air, oxygen or nitrogen.

[0037] Said step a) is preferably carried out at a pressure of 0.8 bar to 3 bar, advantageously from 1 bar to 3 bar, in particular at atmospheric pressure.

[0038] Compound of formula (I)

[0039] Said compound of formula (I) HS-R-SH is such that R is, independently for each -(SRS)- unit, a hydrocarbon substituent having a molecular mass less than 1000 g / mol. Advantageously, R has a molecular mass less than 950 g / mol, preferably less than 900 g / mol, more preferably less than 850 g / mol, particularly less than 800 g / mol, more particularly less than 750 g / mol, preferably less than 700 g / mol, advantageously preferred less than 650 g / mol, preferably preferred less than 600 g / mol, more preferably preferred less than 550 g / mol, particularly preferred less than 500 g / mol. Preferably, R is a hydrocarbon comprising at least one ether, ester, or carbonyl functional group. An ether functional group has the formula A'-O-A2. An ester functional group has the formula A'-C(O)O-A2 or A'-OC(O)-A2.A carbonyl functional group has the formula A*-C(O)-A2. The substituents A1 and A2 are preferably hydrocarbons comprising from 1 to 30 carbon atoms, in particular from 1 to 25 carbon atoms, more particularly from 1 to 20 carbon atoms.

[0040] In said compound of formula (I), R may be of formula -[R'-X-]n-[Y]m- in which

[0041] R1 is, independently for each unit n, selected from the group consisting of Ci-C2o alkyl, C3-C2o cycloalkyl, C6-C2o aryl;

[0042] X is O, C(O), C(O)O, OC(O);

[0043] n is an integer from 1 to 20, advantageously n is an integer from 1 to 15, preferably n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0044] Y is, independently for each unit m, selected from the group consisting of Ci-C2o alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0045] m is an integer from 0 to 20, advantageously m is an integer from 1 to 15, preferably m is an integer from 1 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0046] Advantageously, R can be of the formula -[R'-X-]n-[Y]m- in which

[0047] R1 is, independently for each unit n, selected from the group consisting of C1-C15 alkyl, C3-Ci5 cycloalkyl, C6-Ci5 aryl;

[0048] X is O, C(O), C(O)O, OC(O);

[0049] n is an integer from 1 to 15, preferably n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0050] Y is, independently for each unit m, selected from the group consisting of C1-C15 alkyl, C3-Ci5 cycloalkyl, C6-Ci5 aryl;

[0051] m is an integer from 0 to 15, preferably m is an integer from 1 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0052] Preferably, R can be of the formula -[R'-X-]n-[Y]m- in which

[0053] R1 is, independently for each unit n, selected from the group consisting of C1-C12 alkyl, C3-Ci2 cycloalkyl, C6-Ci2 aryl;

[0054] X is O, C(O), C(O)O, OC(O);

[0055] n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0056] Y is, independently for each unit m, selected from the group consisting of CrCi2alkyl, C3-Ci2 cycloalkyl, C6-Ci2 aryl;

[0057] m is an integer from 0 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0058] More preferably, R can be of the formula -[R'-X-]n-[Y]m- in which

[0059] R1 is, independently for each unit n, selected from the group consisting of C1-C10 alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0060] X is O, C(O), C(O)O, OC(O);

[0061] n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0062] Y is, independently for each unit m, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0063] m is an integer from 0 to 10.

[0064] In particular, R can be of the formula -[R'-X-]n-[Y]m- in which

[0065] R1 is, independently for each unit n, selected from the group consisting in CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl;

[0066] X is O, C(O), C(O)O, OC(O);

[0067] n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0068] Y is, independently for each unit m, selected from the group consisting of CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl;

[0069] m is an integer from 0 to 8, more particularly m is an integer from 1 to 5.

[0070] More particularly, R can be of the formula -[R'-X-]n-[Y]m- in which

[0071] R1 is, independently for each unit n, selected from the group consisting of Ci-C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl;

[0072] X is O, C(O), C(O)O, OC(O);

[0073] n is an integer from 1 to 5;

[0074] Y is, independently for each unit m, selected from the group consisting of C1-C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl;

[0075] m is an integer from 0 to 5, more particularly m is an integer from 1 to 5.

[0076] Preferably, R can be of the formula -[R'-X-]n-[Y]m- in which

[0077] R1 is, independently for each unit n, selected from the group consisting of C1-C5 alkyl, C6-C8 aryl;

[0078] X is O, C(O), C(O)O, OC(O);

[0079] n is an integer from 1 to 5;

[0080] Y is, independently for each unit m, selected from the group consisting of C1-C5 alkyl, C6-C8 aryl;

[0081] m is an integer from 1 to 5.

[0082] R can be of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl.

[0083] Advantageously, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C15 alkyl, C3-Ci5 cycloalkyl, C6-Ci5 aryl.

[0084] Preferably, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C12 alkyl, C3-Ci2 cycloalkyl, C6-Ci2 aryl.

[0085] More preferably, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of CrCio alkyl, C3-C10 cycloalkyl, C6-Ci2 aryl.

[0086] In particular, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl.

[0087] More particularly, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of Cr C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl.

[0088] Preferably, R has the formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of Ci-C5 alkyl, C6-C8 aryl.

[0089] In an advantageously preferred manner, said compound of formula (I) has the formula HS-R2-O-R3-O-R4-SH in which R2, R3 and R4 are selected from the group consisting of C1-C5 alkyl, C6-C8 aryl.

[0090] Preferably, said compound of formula (I) has the formula HS-R2-O-R3-O-R4-SH in which R2, R3 and R4 are selected from the group consisting of CrC3 alkyl.

[0091] In a more preferably preferred manner, said compound of formula (I) is of formula HS-R2-O-R3-O-R4-SH in which R2, R3 and R4 are selected from the group consisting of CH2CH2 and CH(CH3)CH2.

[0092] In particular, said compound of formula (I) is 1,8-dhnercapto-3,6-dioxaoctane. In this case, said polymer PI is poly(1,8-dhnercapto-3,6-dioxaoctane).

[0093] Peroxide

[0094] Said peroxide is preferably selected from among organic peroxides, percarbonates, perborates, persulfates, perphosphates, and hydroperoxides. For example, among the perborates, sodium perborate, potassium perborate, or lithium perborate may be cited. For example, among the percarbonates, sodium percarbonate, potassium percarbonate, or lithium percarbonate may be cited.For example, among organic peroxides and hydroperoxides, we can mention H₂O₂; bis-acylperoxides of the formula (Rf-C(O)-O)₂ with Rf being C₁-C₁₀ (per)haloalkyl, C₁-C₁₀ (per)fluoropolyoxyalkylene, in particular bis-trichloroacetyl peroxide and bis-dichlorofluoroacetyl peroxide; dialkylperoxides of the formula (RH-O)₂ with RH being C₁-C₂O alkyl, in particular diterbutylperoxide (DTBP); dialkylperoxydicarbonates in which the alkyl group has from 1 to 8 carbon atoms such as di-n-propylperoxydicarbonate or diisopropylperoxydicarbonate; alkyl peroxyesters such as tert-amylperoxypivalate or tert-butylperoxyisobutirate. Among the... Examples of persulfates and perphosphates include sodium or potassium persulfate; sodium or potassium perphosphate.

[0095] In particular, the peroxide is H2O2. Indeed, the use of hydrogen peroxide has the added advantage of avoiding the presence of organic impurities or additional processing steps such as precipitation or extractions in the presence of organic solvents, which are energy-intensive. This type of impurity can affect performance in certain electronic applications. The use of hydrogen peroxide also avoids the presence of potentially toxic or flammable organic solvents.

[0096] The concentration Cl of said peroxide solution can be between 0.01% and 70% by weight, advantageously between 0.1% and 65%, preferably between 0.5% and 60%, more preferably between 0.75% and 55% by weight.

[0097] Base

[0098] Said base may be selected from the group consisting of LiOH, NaOH, KOH, CsOH, RbOH, Mg(OH)2, Ca(OH)2, NHx(CnH2n+1)3 x with n being an integer from 1 to 10 and x an integer from 0 to 3, morpholine, pyridine, pyrrolidine, Piperidine, piperazine, 4-Methylmorpholine, N,N-Diisopropylethylamine, 1,8-Diazabicyclo(5.4.0)undec-7-ene, 6-(Dibutylamino)-1,8-diazabicyclo[5.4.0]undec-7-ene, 1,8-Diazabicyclo[5.4.0]undec-7-ene bonded to polystyrene, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene, 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-Tetramethylguanidine, 2-tert-Butyl-1,1,3,3-tetramethylguanidine, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene linked to polystyrene, 1,4-Diazabicyclo[2.2.2]octane, Quinuclidine, 1,5-Diazabicyclo(4.3.0)non-5-ene, 2,6-Di-tert-butylpyridine, 2,8,9-Trimethyl-2,5,8,9-tetraza-1-phosphabicyclo[3.3.3]undecane, Cyclodiphosphazane, Lithium diisopropylamide, sodium diisopropylamide, potassium diisopropylamide, magnésium diisopropylamide, calcium diisopropylamide, rubidium diisopropylamide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)a mide, potassium bis(trimethylsilyl)amide, magnésium bis(trimethylsilyl)amide, calcium bis(trimethylsilyl)amide, rubidium bis(trimethylsilyl)amide, lithium tetramethylpiperidide, sodium tetramethylpiperidide, potassium tetramethylpiperidid e, magnésium tetramethylpiperidide, calcium tetramethylpiperidide, rubidium tetramethylpiperidide, [18-crown-6]-KHF2, KHF2, N,N’-diisopropylimidazonium, bifluorure, tetrabutylammonium, N(CnH2n+i)4+OH avec n étant un entier de 1 à 10. .

[0099] Preferably, said base may be selected from the group consisting of LiOH, NaOH, KOH, CsOH, RbOH, Mg(OH)2, Ca(OH)2, NHx(CnH2n+1)3 x with n being an integer from 1 to 8 and x an integer from 0 to 2, morpholine, pyridine, pyrrolidine, Piperidine, piperazine, 4-Methylmorpholine, N,N-Diisopropylethylamine, 1,8-Diazabicyclo(5.4.0)undec-7-ene and 6-(Dibutylamino)-1,8-diazabicyclo[5.4.0]undec-7-ene.

[0100] In particular, said base may be selected from the group consisting of LiOH, NaOH, KOH, CsOH, RbOH, Mg(OH)2, Ca(OH)2, NHx(CnH2n+1)3 x with n being an integer from 1 to 5 and x an integer from 0 to 1, morpholine, pyridine, pyrrolidine, Piperidine, piperazine, 4-Methylmorpholine, N,N-Diisopropylethylamine, 1,8-Diazabicyclo(5.4.0)undec-7-ene and 6-(Dibutylamino)-1,8-diazabicyclo[5.4.0]undec-7-ene.

[0101] More particularly, said base is selected from the bases mentioned above having a saturated vapor pressure greater than 1kPa at 20°C, advantageously greater than 2kPa at 20°C, preferably greater than 3kPa at 20°C, more preferably greater than 4kPa at 20°C, in particular greater than 5kPa at 20°C.

[0102] Step b)

[0103] The process according to the present invention may also include a step b) of purifying said PI polymer obtained in step a). Said step b) includes a step of removing said base used in step a) or a step of filtering said PI polymer or a combination of both.

[0104] Said step of removing said base used in step a) is preferably carried out by heat treatment of said PI polymer at a temperature of 20°C to 150°C and a pressure of 0.01 bara to 1 bara, prior to and / or after said filtration of said PI polymer. Said temperature may be from 20°C to 140°C, advantageously from 20°C to 130°C, preferably from 20°C to 120°C, more preferably from 20°C to 110°C, in particular from 20°C to 100°C, more particularly from 20°C to 90°C, preferably from 20°C to 80°C.

[0105] Said filtration step of said polymer PI can be implemented using a filtration device comprising a membrane made of at least one fluorinated polymer or a polyolefin.Said fluorinated polymer may comprise monomeric units derived from a monomer selected from the group consisting of vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF2=CFOCF2CF(CF3)OCF2CF2X in which X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; the product of formula CF2 =CFOCF2CF2SO2F; the product of formula F(CF2)nCH2OCF=CF2 in which n is 1, 2, 3, 4 or 5; the product of formula R1CH2OCF=CF2 in which R1 is hydrogen or F(CF2)m and m is 1, 2, 3 or 4; the product of formula R2OCF=CH2 in which R2 is F(CF2)p and p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); . trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Among the trifluoropropenes is 3,3,3-trifluoropropne. Examples of tetrafluoropropenes include 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene. Examples of pentafluoropropenes include 1,1,3,3,3-pentafluoropropene and 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene can refer to either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene. Advantageously, said fluorinated polymer may comprise monomeric units derived from a monomer selected from the group consisting of vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene.Preferably, said fluorinated polymer may comprise monomeric units derived from a monomer selected from the group consisting of vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene. In particular, said fluorinated polymer may be a homopolymer of tetrafluoroethylene, a homopolymer of vinylidene fluoride, or a copolymer comprising monomeric units derived from tetrafluoroethylene or vinylidene fluoride.

[0106] Said polyolefin may be polyethylene, polypropylene, polymethylpropene, polybutene, polypentene, polymethylpentene, polymethylbutene, polyhexene, polymethylpentene and polyethylbutene.

[0107] Preferably, said membrane comprises pores of a size from 1 nm to 100 nm, advantageously from 1 nm to 75 nm, preferably from 2 nm to 50 nm, more preferably from 3 nm to 25 nm, in particular from 3 nm to 10 nm.

[0108] In particular, said membrane may be made of a tetrafluoroethylene homopolymer, a vinylidene fluoride homopolymer, a copolymer comprising monomeric units derived from tetrafluoroethylene or vinylidene fluoride, and may comprise pores with a size of 1 nm to 100 nm, advantageously from 1 nm to 75 nm, preferably from 2 nm to 50 nm, more preferably from 3 nm to 25 nm, in particular from 3 nm to 10 nm. The pore size is preferably determined according to standard 4003:1977.

[0109] PI Polymer

[0110] The present invention enables the preparation of said PI polymer.

[0111] said PI polymer comprises at least one segment -(SRS)-(SRS)- with R being, independently for each unit -(SRS)-, a hydrocarbon substituent having a molecular mass less than 1000 g / mol. Advantageously said substituent R has a molecular mass less than 950 g / mol, preferably said substituent R has a molecular mass less than 900 g / mol, more preferably said substituent R has a molecular mass less than 850 g / mol, in particular said substituent R has a molecular mass less than 800 g / mol, more particularly said substituent R has a molecular mass less than 750 g / mol, preferably said substituent R has a molecular mass less than 700 g / mol, advantageously preferred said substituent R has a molecular mass less than 650 g / mol, preferably preferred said substituent R has a molecular mass less than 600 g / mol, more preferably preferred said substituent R has a molecular mass less than 550 g / mol, particularly preferred said substituent R has a molecular mass less than 500 g / mol.

[0112] Preferably, in said polymer PI, R is a hydrocarbon comprising at least one ether, ester, or carbonyl functional group. An ether functional group has the formula A'-O-A2. An ester functional group has the formula A'-C(O)OA2 or A'-OC(O)-A2. A carbonyl functional group has the formula A'-C(O)-A2. The substituents A1 and A2 are preferably hydrocarbons comprising from 1 to 30 carbon atoms, in particular from 1 to 25 carbon atoms, more particularly from 1 to 20 carbon atoms.

[0113] In said PI polymer, R can be of formula -[R'-X-]n-[Y]m- in which

[0114] R1 is, independently for each unit n, selected from the group consisting of Ci-C2o alkyl, C3-C2o cycloalkyl, C6-C2o aryl;

[0115] X is O, C(O), C(O)O, OC(O);

[0116] n is an integer from 1 to 20, advantageously n is an integer from 1 to 15, preferably n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0117] Y is, independently for each unit m, selected from the group consisting of Ci-C20 alkyl, C3-C10 cycloalkyl, C6-Ci2 aryl;

[0118] m is an integer from 0 to 20, advantageously m is an integer from 1 to 15, preferably m is an integer from 1 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0119] Advantageously, in said PI polymer, R can be of formula -[R'-X-]n-[Y]m- in which

[0120] R1 is, independently for each unit n, selected from the group consisting of C1-C15 alkyl, C3-Ci5 cycloalkyl, C6-Ci5 aryl;

[0121] X is O, C(O), C(O)O, OC(O);

[0122] n is an integer from 1 to 15, preferably n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0123] Y is, independently for each unit m, selected from the group consisting of C1-C15 alkyl, C3-Ci5 cycloalkyl, C6-Ci5 aryl;

[0124] m is an integer from 0 to 15, preferably m is an integer from 1 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0125] Preferably, in said PI polymer, R may be of formula -[R'-X-]n-[Y]m- in which

[0126] R1 is, independently for each unit n, selected from the group consisting of C1-C12 alkyl, C3-Ci2 cycloalkyl, C6-Ci2 aryl;

[0127] X is O, C(O), C(O)O, OC(O);

[0128] n is an integer from 1 to 12, more preferably n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0129] Y is, independently for each unit m, selected from the group consisting of CrCi2alkyl, C3-Ci2 cycloalkyl, C6-Ci2 aryl;

[0130] m is an integer from 0 to 12, more preferably m is an integer from 1 to 10, in particular m is an integer from 1 to 8, more particularly m is an integer from 1 to 5.

[0131] More preferably, in said PI polymer, R can be of the formula -[R'-X-]n-[Y] m- in which

[0132] R1 is, independently for each unit n, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0133] X is O, C(O), C(O)O, OC(O);

[0134] n is an integer from 1 to 10, in particular n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0135] Y is, independently for each unit m, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl;

[0136] m is an integer from 0 to 10.

[0137] In particular, in said PI polymer, R may be of the formula -[R'-X-]n-[Y]m- in which

[0138] R1 is, independently for each unit n, selected from the group consisting of CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl;

[0139] X is O, C(O), C(O)O, OC(O);

[0140] n is an integer from 1 to 8, more particularly n is an integer from 1 to 5;

[0141] Y is, independently for each unit m, selected from the group consisting of CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl;

[0142] m is an integer from 0 to 8, more particularly m is an integer from 1 to 5.

[0143] More particularly, in said PI polymer, R can have the formula -[R'-X-]n-[Y]m- in which

[0144] R1 is, independently for each unit n, selected from the group consisting of Ci-C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl;

[0145] X is O, C(O), C(O)O, OC(O);

[0146] n is an integer from 1 to 5;

[0147] Y is, independently for each unit m, selected from the group consisting of C1-C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl;

[0148] m is an integer from 0 to 5, more particularly m is an integer from 1 to 5.

[0149] Preferably, in said PI polymer, R can be of formula -[R'-X-]n-[Y] m- in which

[0150] R1 is, independently for each unit n, selected from the group consisting of C1-C5 alkyl, C6-C8 aryl;

[0151] X is O, C(O), C(O)O, OC(O);

[0152] n is an integer from 1 to 5;

[0153] Y is, independently for each unit m, selected from the group consisting of C1-C5 alkyl, C6-C8 aryl;

[0154] m is an integer from 1 to 5.

[0155] In a preferred embodiment, in said polymer PI, R is of formula -R-OR-OR- in which R, R and R are independently of each other, selected from the group consisting of C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl.

[0156] Advantageously, in said PI polymer, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C15 alkyl, C3-C15 cycloalkyl, C6-Ci5 aryl.

[0157] Preferably, in said PI polymer, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C12 alkyl, C3-C12 cycloalkyl, C6-Ci2 aryl.

[0158] More preferably, in said polymer PI, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C10 alkyl, C3-C10 cycloalkyl, C6-Ci2 aryl.

[0159] In particular, in said PI polymer, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of CrC8 alkyl, C3-C8 cycloalkyl, C6-Ci0 aryl.

[0160] More particularly, in said PI polymer, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of C1-C5 alkyl, C3-C5 cycloalkyl, C6-C8 aryl.

[0161] Preferably, in said PI polymer, R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of Ci-C5 alkyl, C6-C8 aryl.

[0162] Advantageously preferred, said PI polymer comprises, advantageously is constituted, repeating units of formula -(-S-R2-O-R3-O-R4 -SS-R2-O-R3-O-R4-S-)- in which R2, R3 and R4 are selected from the group consisting of Ci-C5 alkyl, C6-C8 aryl.

[0163] In a preferred manner, said PI polymer comprises, advantageously is constituted, repeating units of formula -(-S-R2-O-R3-O-R4 -SS-R2-O-R3-O-R4-S-)- in which R2, R3 and R4 are selected from the group consisting of CrC3 alkyl.

[0164] More preferably, said PI polymer comprises, advantageously is made up of, repeating units of formula -(-S-R2-O-R3-O-R4 -SS-R2-O-R3-O-R4-S-)- in which R2, R3 and R4 are selected from the group consisting of CH2CH2 and CH(CH3)CH2.

[0165] In a particularly preferred manner, said PI polymer is poly(l,8-dimercapto-3,6-dioxaoctane).

[0166] Said PI polymer may have a molar mass greater than 10,000 g / mol. Advantageously, said PI polymer may have a molar mass greater than 15,000 g / mol. Preferably, said PI polymer may have a molar mass greater than 20,000 g / mol. More preferably, said PI polymer may have a molar mass greater than 25,000 g / mol. In particular, said PI polymer may have a molar mass greater than 30,000 g / mol.

[0167] Said PI polymer can be linear or cyclic. The ring can be formed via a reaction between two sulfur atoms resulting in the formation of a ring via a disulfide bond.

[0168] Composition

[0169] The present invention provides a composition comprising at least 99.5% by mole of said PI polymer according to the present invention.

[0170] Said composition may include traces of metals. For example, said composition may include from 1 ppb to 100 ppm by mole of sodium. It may optionally include from 1 ppb to 50 ppm by mole of silver and / or zinc.

[0171] Said composition may also include less than 10 ppm by mole of a metal selected from the group consisting of iron, aluminum, copper and magnesium on the basis of said total composition.

[0172] Said composition may also include less than 10 ppm by mole of a metal selected from the group consisting of calcium, potassium, phosphorus or silicon on the basis of said total composition.

[0173] Preferably, said composition comprises less than 0.5% by mole of said base on the basis of the total composition. The molar content of said base in the composition may be less than 0.45%, advantageously less than 0.40%, preferably less than 0.35%, more preferably less than 0.30%, in particular less than 0.25%, more particularly less than 0.20%, preferably less than 0.15%, advantageously less than 0.1%, preferably less than 0.05%, more preferably less than 0.01%, particularly less than 0.005%.

[0174] Preferably, said composition comprises less than 0.1% by mole of water on the basis of the total composition. The molar water content in the composition may be less than 0.09%, advantageously less than 0.08%, preferably less than 0.07%, more preferably less than 0.06%, in particular less than 0.05%, more particularly less than 0.04%, preferably less than 0.03%, advantageously preferred less than 0.02%, preferably preferred less than 0.01%, more preferably preferred less than 0.005%, particularly preferred less than 0.001%, more particularly preferred less than 0.0001%.The molar water content in the composition may be less than 90 ppm, advantageously less than 80 ppm, preferably less than 70 ppm, more preferably less than 60 ppm, particularly less than 50 ppm, more particularly less than 40 ppm, preferably less than 30 ppm, advantageously preferred less than 20 ppm, preferably preferred less than 10 ppm.

[0175] The molar content of said base and of water in the composition can be determined by 'H NMR.

[0176] Usage

[0177] The composition can be used in many applications.

[0178] The present invention provides, in particular, a film comprising the composition according to the present invention. The present invention also provides an electrochemical device comprising said film according to the present invention. Examples Measurement of average molecular mass by weight

[0179] The weight-average molecular weight was measured on a Waters Alliance 2695-15 instrument with two detectors: a Waters 2414 RI and a Waters 2487 Dual UV 254 nm, equipped with two PL gel 10 µm Mixed-B 300 x 7.5 mm columns. The flow rate was 1 ml / min, the eluent was BHT-stabilized THF, and the sample concentration was 1 g / L dissolved at room temperature for at least 4 hours. The injected volume was 5 µL. Calibration was performed with Easivial PS-H standards from 580 to 6545000 g / mol.

[0180] Example s 1 af ; Preparation of poly(L8-dimercapto-3,6-dioxaoctane)

[0181] In a container, 15 mL of 1,8-dihnercapto-3,6-dioxaoctane (0.09 mol) were mixed with 25 mL of triethylamine (0.19 mol, 2.2 eq). After 5 min of mixing, 25 mL of water were added, resulting in a dispersion. 25 mL of hydrogen peroxide solution (35 wt% in water) were then added to the mixture via 5 mL injections to maintain controllable exothermicity. The temperature was raised from 16 °C to 35 °C, and after 3 hours of mixing, a white polymer formed alongside a clear water phase, and the bath temperature dropped to room temperature, indicating the end of the reaction. The polymer was then isolated by decantation from the liquid phase. The weight-average molecular weight Mw is 850 kg / mol.

[0182] The example above is reproduced with a hydrogen peroxide solution having a concentration of 1%, 3%, 5%, 10% and 30% respectively. Table 1 below details the average molecular mass by weight obtained.

[0183] [Tables 1] Examples 1b le Id le If Cl 35% 1% 3% 5% 10% 30% Mw (kg / mo 1) 850.0 30.8 52.8 106.0 115.6 552.9

[0184] Cl refers to the concentration of the peroxide solution introduced into the reaction medium

[0185] As demonstrated by the examples above, the concentration of the peroxide solution used makes it possible to effectively control the average molecular mass by weight.

[0186] Example 2: Purification of poly(L8-dimercapto-3,6-dioxaoctane)

[0187] The polymer obtained in Example 1 is dried in a ventilated oven at 50 °C for 6 h under vacuum (25 mbar), resulting in a white polymer film. Residual triethylamine and water were quantified by NMR: Triethylamine: 0 mol% (not detectable), water: 0 mol% (not detectable). The polymer is dissolved in The polymer is dissolved in 10% anhydrous THF. After dissolution, it is precipitated in methanol, and the solution is then filtered and dried under vacuum at 40°C. The recovered polymer is again solubilized in a 5% anhydrous THF solution. The solution is filtered through a PTFE membrane filter with a pore size of 3 nm to 10 nm to remove metallic impurities. The polymer is then dried again in a ventilated oven at 30°C. The resulting polymer has a metal content of less than 40 ppm. Comparative example 3

[0188] The polymer obtained in Example 1 was heated in a ventilated oven at 80 °C for 12 h, yielding a white product. Residual triethylamine and water were quantified by NMR: Triethylamine: 0.9 mol%, water: 13.8 mol%.

[0189] A film was prepared from the polymers of Example 2 according to the invention and of Comparative Example 3, respectively. This film was deposited on a lithium metal anode. The anode on which a film made of the polymer from Comparative Example 3 was deposited degrades rapidly, unlike the anode on which a film made of the polymer from Example 2 according to the invention was deposited. Cyclic voltammetry was performed on the purified polymer according to Example 2 and according to Comparative Example 3. The cyclic voltammetry was carried out between 2 and 5 V at 0.1 mV / s. Figure 1 shows the cyclic voltammetry with the polymer according to Example 2. The film prepared with the polymer according to Example 2 is more electrochemically stable than the film prepared with the polymer according to Comparative Example 3, which degrades rapidly.The electrochemical stability of the polymer according to example 2 is sufficient for use in Li-ion batteries, including with high voltage positive active materials (nickel-rich NMC type).

Claims

Demands

1. A process for preparing a PI polymer comprising at least one disulfide bond, said process comprising: a. A polymerization step, preferably in aqueous medium, by adding a solution of a peroxide to a dispersion, preferably aqueous, comprising at least one compound of formula (I) HS-R-SH and a base for forming said PI polymer comprising at least one -(SRS)-(SRS)- segment with R being, independently for each -(SRS)- unit, a hydrocarbon substituent having a molecular mass less than 1000 g / mol.

2. A preparation process according to the preceding claim characterized in that said PI polymer has a weight average molecular mass Mw, expressed in kg / mol, between: ((2226 + 1951754*C1)*0.00055) < Mw < ((2226 + 1951754*C1)*0.00145); Cl being the concentration of said peroxide solution, expressed in % by weight.

3. A process according to any one of the preceding claims characterized in that it comprises a step b) of purification of said PI polymer obtained in step a) comprising a step of removal of said base used in step a) or a step of filtration of said PI polymer or a combination of both.

4. A process according to the preceding claim characterized in that said step of removing said base used in step a) is carried out by heat treatment of said PI polymer at a temperature of 20°C to 100°C and a pressure of 0.01 bara to 1 bara, prior to and / or subsequent to said filtration of said PI polymer.

5. A method according to the preceding claim characterized in that said filtration step of said PI polymer is carried out using a filtration device comprising a membrane made of at least one fluorinated polymer or a polyolefin.

6. A method according to the preceding claim characterized in that said membrane comprises pores with a size of 1 nm to 100 nm, advantageously from 1 nm to 75 nm, preferably from 2 nm to 50 nm, more preferably from 3 nm to 25 nm, in particular from 3 nm to 10 nm.

7. A method according to any one of the preceding claims characterized in that said base used in step a) has a saturated vapor pressure greater than IkPa at 20°C.

8. A process according to any one of the preceding claims characterized in that said peroxide used in step a) is selected from the group consisting of organic peroxides, percarbonates, perborates, persulfates, perphosphates and hydroperoxides.

9. A process according to any one of the preceding claims characterized in that said compound of formula (I) is HS-R-SH in which R is a hydrocarbon comprising at least one ether, ester or carbonyl functional group.

10. A method according to any one of the preceding claims characterized in that R is of formula -[R'-X-]n-[Y]m- in which R1 is, independently for each unit n, selected from the group consisting of Ci-Cio alkyl, C3-CiO cycloalkyl, C6-Ci2 aryl; X is O, C(O), C(O)O, OC(O); n is an integer from 1 to 20; Y is, independently for each unit m, selected from the group consisting of CrCio alkyl, C3-CiO cycloalkyl, C6-Ci2 aryl; m is an integer from 0 to 20.

11. A method according to any one of the preceding claims characterized in that R is of formula -R2-O-R3-O-R4- in which R2, R3 and R4 are independently of each other, selected from the group consisting of Ci-Cio alkyl, C3-Ci0 cycloalkyl, C6-Ci2 aryl.

12. A process according to any one of the preceding claims characterized in that said compound of formula (I) is 1,8-dimercapto-3,6-dioxaoctane and in that said polymer PI is poly(1,8-dimercapto-3,6-dioxaoctane).

13. A process according to any one of the preceding claims, characterized in that said base is selected from the group consisting of LiOH, NaOH, KOH, CsOH, RbOH, Mg(OH)2, Ca(OH)2, NHx(CnH2n+1)3, x with n being an integer from 1 to 10 and x an integer from 0 to 3, N,N-Diisopropylethylamine, morpholine, pyridine, pyrrolidine, Piperidine, piperazine, 4-Methylmorpholine, 1,8-Diazabicyclo(5.4.0)undec-7-ene, 6-(Dibutylamino)-1,8- diazabicyclo[5.4.0]undec-7-ene, 1,8-Diazabicyclo[5.4.0]undec-7-ene bonded to polystyrene, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene, 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-Tetramethylguanidine, 2-tert-Butyl-1,1,3,3-tetramethylguanidine, 1,5,7-Triazabicyclo[4.4.0]dec-5-ene bonded to polystyrene, 1,4-Diazabicyclo[2.2.2]octane, Quinuclidine, 1,5-Diazabicyclo(4.3.0)non-5-ene, 2,6-Di-tert-butylpyridine, 2,8,9-Trimethyl-2,5,8,9-tetraza-l-phosphabicyclo[3.3.3]undecane, Cyclodiphosphazane, Lithium diisopropylamide, sodium diisopropylamide, potassium diisopropylamide, magnésium diisopropylamide, calcium diisopropylamide, rubidium diisopropylamide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, magnésium bis(trimethylsilyl)amide, calcium bis(trimethylsilyl)amide, rubidium bis(trimethylsilyl)amide, lithium tetramethylpiperidide, sodium tetramethylpiperidide, potassium tetramethylpiperidide, magnésium tetramethylpiperidide, calcium tetramethylpiperidide, rubidium tetramethylpiperidide, [18-crown-6]-KHF2, KHF2, N,N’-diisopropylimidazonium, bifluorure, tetrabutylammonium, N(CnH2n+i)4+OH avec n étant un entier de 1 à.

14. IV. Composition comprising at least 99.5 mole percent of said PI polymer as defined according to any one of claims 1, 9 to 12; said PI polymer having a weight-average molecular mass Mw greater than 10000 g / mol, preferably greater than 15000 g / mol, in particular greater than 20000 g / mol.

15. Composition according to the preceding claim characterized in that it comprises: - from 1 ppb to 100 ppm in mole of sodium; - less than 10 ppm in mole of a metal selected from the group consisting of iron, aluminum, copper and magnesium; based on said total composition.

16. Composition according to any one of the preceding claims 14 or 15 characterized in that it comprises less than 0.5% by mole of said base as defined in claim 13 on the basis of the total composition.

17.

18.

19.

20. Composition according to any one of the preceding claims 14 to 16 characterized in that it comprises less than 0.1% by mole of water on the basis of the total composition. Film comprising the composition according to any one of claims 14 to 17. Electrochemical device comprising said film according to the preceding claim. Poly(l,8-dimercapto-3,6-dioxaoctane) having a weight average molecular mass Mw greater than 10000 g / mol, and comprising less than 0.1% by weight of water.