EP4698578A1

EP4698578A1 - Polyarylene polymers

Info

Publication number: EP4698578A1
Application number: EP24720470.4A
Authority: EP
Inventors: Nicolas TREAT; Bryan Benson; Eduardo Salvador SORIANO-JUAREZ; Wheeler LOVETT
Original assignee: Syensqo Specialty Polymers USA LLC
Current assignee: Syensqo Specialty Polymers USA LLC
Priority date: 2023-04-19
Filing date: 2024-04-17
Publication date: 2026-02-25
Also published as: WO2024218158A1; JP2026513364A; CN121039194A; WO2024218157A1; EP4698577A1; KR20250174925A

Abstract

A process for the conversion of a polyarylene polymer comprising sulfonic acid ester functional groups into a polyarylene polymer comprising sulfonic acid functional groups which comprises a heat treatment step.

Description

POLYARYLENE POLYMERS

Reference to related applications

This application claims priority to U.S. provisional application 63/460374 - filed April 19^th, 2023 - and to European patent application No. 23187892.7 - filed July 26^th, 2023 the whole content of each of these applications being incorporated herein by reference for all purposes.

Technical Field

[0001] The invention relates to a method for preparing polyarylene polymers having sulfonic acid functional groups from polyarylene polymers having sulfonic acid ester functional groups.

Background Art

[0002] The use of polymer electrolyte materials as ion conducting materials in electrochemical devices is known. Polymers having proton conductivity, namely polymer electrolytes are used as the separating membrane of electrochemical devices such as electrolysis cells, redox flow batteries and fuel cells. For example, perfluoroalkylsulfonic acid polymers have been used as a membrane material for fuel cells for several decades.

[0003] Polyarylene polymer electrolytes comprising sulfonic acid functional groups are also known. Polyarylene polymers comprising sulfonic acid functional groups can be obtained starting from monomers comprising sulfonate esters or sulfonamide functional groups.

[0004] EP1935916A1 discloses polymers comprising recurring units of formula wherein A represents an amino group substituted with one or two hydrocarbon groups wherein the sum of number of carbon atoms of the hydrocarbon group or groups is 3 to 20, or a C3-C20 alkoxy group, R1 represents a hydrogen atom, a fluorine atom, a C1-C20 alkyl group, a C1-

SUBSTITUTE SHEET (RULE 26) C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2- C20 acyl group or a cyano group, and the C1 -C20 alkyl group, the C1 -C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1 -C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R¹s exist, R¹s may be the same groups or different groups, and the neighboring two R¹s may be bonded to form a ring, m represents 1 or 2, and k represents 4-m which are obtained from the corresponding halides.

[0005] US2014/0154610A1 discloses aromatic copolymers comprising a hydrophilic segment (A) and a hydrophobic segment (B), wherein the hydrophilic segment (A) comprises a structural unit having a proton conductive group, and the hydrophobic segment (B) comprises at least one structural unit selected from the group consisting of a structural unit which is a divalent structural unit having an aromatic ring and no proton conductive groups and having two bonding sites at the para-position of one ring included in the aromatic ring, and a divalent structural unit having a benzene ring. Notable example of structural units having a proton conducting group is for instance : wherein Ar¹¹ , Ar¹² and Ar¹³ are each independently a benzene ring, a condensed aromatic ring, or an aromatic group having a nitrogencontaining heterocyclic ring, which may be substituted by a halogen atom, a C1 -20 monovalent hydrocarbon group or a C1 -20 monovalent halogenated hydrocarbon group, Y and Z are each independently a direct bond, -O-, -S-, -CO-, -SO2-, -SO-, -(CH2)u-, -(CF2)u- where u is an integer of 1 to 10, -C(CH3)2-, or -C(CF3)2-, R¹⁷ is independently a direct bond, - O(CH2)_P-, -O(CF2)_P-, -(CH2)_P- or -(CF2)_P- where p is an integer of 1 to 12, R¹⁸ and R¹⁹ are each independently a hydrogen atom or a protective group, wherein at least one of all R¹⁸s and R¹⁹s which are contained in the structural unit (1 ) is a hydrogen atom, x1 is independently an integer of 0 to 6, x² is an integer of 1 to 7, a is 0 or 1 , and b is an integer of 0 to 20.

[0006] WO2014/208714A1 discloses a polyarylene polymer comprising recurring units of formula in which R⁴ is hydrogen, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and the substituents may be the same or different; r is 1 or 2, and d is 4-r. A represents OR⁵ or N(R⁶)(R⁷), R⁵ represents either hydrogen, an alkali metal, or an alkyl group having 1 to 20 carbon atoms, and R⁶ and R⁷ represent hydrogen or an alkyl group having 1 to 20 carbon atoms, either, and R⁶ and R⁷ may be the same or different. The recurring units are obtained from the corresponding dihalide monomers. The use of the polyarylene polymers in the preparation of electrolyte membranes is also disclosed.

[0007] According to the prior art disclosures, transformation of the sulfonic acid ester group or the sulfonamide group into the sulfonic acid functional group is achieved either by hydrolysis in acid or alkaline environment or by reaction with an alkali metal halide followed by ion exchange with an acid. Said transformation is generally carried out before the polyarylene polymer is shaped into an article, such as a film or a membrane.

[0008] It has now surprisingly been found that the transformation of the sulfonic acid ester functional group into a sulfonic acid functional group can be successfully accomplished by thermal treatment of the polyarylene polymer in the absence of any chemical treatment, such as hydrolysis with an acid or an alkali or reaction with an alkaline halide.

[0009] Accordingly an object of the invention is a process for converting sulfonic acid ester groups into sulfonic acid groups in a polyarylene polymer comprising recurring units of formula (A) as defined hereafter: said process comprising heating the polyarylene polymer to a temperature of 100°C to 200°C. The conversion is achieved by thermal treatment in the absence of any chemical treatment, such as hydrolysis with an acid or an alkali or reaction with an alkaline halide.

Summary of invention

[0010] A first object of the invention is a process for converting sulfonic acid ester groups into sulfonic acid groups in a polyarylene polymer comprising recurring units of formula (A) as defined hereafter: said process comprising heating the polyarylene polymer to a temperature of 100°C to 200°C. The conversion is achieved by thermal treatment in the absence of any chemical treatment, such as hydrolysis with an acid or an alkali or reaction with an alkaline halide.

[0011 ] The invention further relates to films comprising a polyarylene polymer comprising recurring units of formula (A) as well as methods to prepare these films and further process them into ion exchange membranes.

Description of invention

[0012] In the present application:

- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present disclosure;

- where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list;

- the indeterminate article “a” in an expression like “a recurring unit”, is intended to mean “one or more”, or “at least one” unless indicated otherwise;

- the use of brackets “( )” before and after names of compounds, symbols or numbers, e.g. “Polymer (GP)”, “Polymer (GPA)”, etc... , has the mere purpose of better distinguishing that name, symbol or number from the rest of the text; thus, said parentheses could also be omitted; and

- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents;

- the proportions of recurring units in a polymer are given relative to the total moles of recurring units in the polymer;

- the expression “percent by weight” (wt%) indicates the content of a specific component in a mixture, calculated as the ratio between the weight of the component and the total weight of the mixture. As used herein, the concentration of recurring units in “percent by mol” (mol%) refers to the concentration of a given type of recurring unit relative to the total number of recurring units in the polymer, unless explicitly stated otherwise;

- as used herein, the terminology “Cn-Cm” in reference to an organic group, wherein n and m are integers, respectively, indicates that the group may contain from n carbon atoms to m carbon atoms per group.

[0013] Object of the invention is a process for converting sulfonic acid ester groups into sulfonic acid groups in a polyarylene polymer comprising recurring units of formula (A), hereinafter referred to as [Polymer (GP)]: in which R¹ is a C1-C20 alkoxy group, optionally substituted; each R^x, independently of each other, is selected from the group consisting of a hydrogen atom, a fluorine atom, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1-C20 alkyl group, the C1-C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1-C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R^xs exist the neighboring two R^xs may be bonded to form a ring, and p is 1 or 2, said process comprising heating the polyarylene polymer, [Polymer (GP)], to a temperature of 100°C to 200°C.

The conversion is achieved by thermal treatment in the absence of any chemical treatment, such as hydrolysis with an acid or an alkali or reaction with an alkaline halide. The expression “chemical treatment” means hydrolysis with an acid or an alkali or reaction with an alkaline halide.

[0014] In formula (A) p is preferably 1 .

[0015] Examples of the C1-C20 alkoxy group R¹ in formula (A) include linear, branched chain or cyclic C1-C20 alkoxy. Notable examples are for instance methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy, 2,2-methylpropoxy, cyclopentyloxy, n- hexyloxy, cyclohexyloxy, n-heptyloxy, 2-methylpentyloxy, n-octyloxy, 2- ethylhexyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, n- tridecyloxy, n-tetradecyloxy, n-pentadecyloxy, n-hexadecyloxy, n- heptadecyloxy, n-octadecyloxy, n-nonadecyloxy and n-icosyloxy groups. Alkoxy group R¹ is preferably isobutoxy, 2,2-dimethylpropoxy or cyclohexyloxy. Alkoxy group R¹ is more preferably 2,2-dimethylpropoxy.

[0016] Each R^x, independently of each other, is selected from the group consisting of a hydrogen atom, a fluorine atom, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2- C20 acyl group or a cyano group. R^x is preferably hydrogen.

[0017] Polymer (GP) may consist of one or more recurring units of formula (A) or it may comprise further recurring units. [0018] Polymer (GP) may advantageously comprise, in addition to recurring units of formula (A), also recurring units of formula (B): in which each Ry, independently of each other, is selected from the group consisting of a fluorine atom, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1-C20 alkyl group, the C1-C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1-C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple Rys exist the neighboring two Rys may be bonded to form a ring, and q is an integer from 1 to 4.

[0019] One or more than one recurring unit of formula (B), different from one another, may be present in Polymer (GP).

[0020] Polymer (GP) may additionally comprise recurring units of formula (C): in which R^z1 and R^z2, independently of each other, is selected from the group consisting of a fluorine atom, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1-C20 alkyl group, the C1-C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1-C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R^Z1 and R^z2 exist the neighboring ones may be bonded to form a ring; r and s are independently of each other an integer from 1 to 4; and Z is selected from the group consisting of an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, 2,2 isopropylidene group, 2,2 hexafluoroisopropylidene group.

[0021 ] In Polymer (GP) the amount of recurring units of formula (A) is from 0.1 to 90.0 mol% with respect to the total amount of recurring units in the polymer. The amount of recurring units of formula (A) is generally from 5.0 to 70.0 mol%, from 10.0 to 65.0 mol%, even from 25.0 to 60.0 mol%, from 35.0 to 55.0 mol%. The remainder of the units in Polymer (GP) may consist of one or more recurring units of formula (B) or of one or more recurring units of formula (B) and (C).

[0022] The bonds connecting recurring units of formula (A) and/or (B) and/or (C) in Polymer (GP) may have an ortho, meta or para configuration. Preferably a meta and/or para configuration.

[0023] Polymer (GP) can be synthesized by known methods, such as those disclosed in EP1935916A1 , US20140154610A1 and WO2014208714A1 .

[0024] Polymer (GP) may be prepared by polymerizing a dihalo compound (I) that gives the structural unit (A) and optionally a compound (II) that gives the structural unit (B) and/or a compound (III) that gives the structural unit (C):

(II) (HI) wherein R^x, R¹, p, Ry, q, R^z1 and R^z2, Z are as defined above and each X is independently selected from the group consisting of halogens, mesylate, tosylate or trif late. Preferably, X is chlorine.

[0025] The polymerization is carried out preferably in the presence of a catalyst. Any catalyst for the polymerization of aromatic dihalide compounds may be used.

[0026] Typically, Polymer (GP) can be produced by polymerizing a monomer composition comprising the compounds (I) and optionally (II) and/or (III) in the presence of a nickel compound. Examples of the nickel compound include a zerovalent nickel compound such as bis(cyclooctadiene)nickel(0), (ethylene)bis(triphenylphosphine)nickel(0) and tetrakis(triphenylphosphine)nickel(0), and a divalent nickel compound such as a nickel halide (e.g. nickel fluoride, nickel chloride, nickel bromide, nickel iodide etc.), bis(triphenylphosphine)nickel chloride, nickel carboxylate (e.g. nickel formate, nickel acetate etc.), nickel sulfate, nickel carbonate, nickel nitrate, nickel acetylacetonate and (dimethoxyethane)nickel chloride. Nickel chloride and nickel bromide are preferable.

[0027] The polymerization reaction is preferably conducted in the presence of the nickel compound and a nitrogen-containing or phosphorous-containing ligand. Examples of the nitrogen-containing ligands include 1 ,10- phenanthroline, methylenebisoxazoline and N,N'- tetramethylethylenediamine. Examples of the phosphorous-containing ligand include triphenylphosphine, tri(2-methyl)phenylphosphine, tri(3- methyl)phenylphosphine, tri(4-methyl)phenylphosphine, 1 ,5- cyclooctadiene, 1 ,3-bis(diphenylphosphino)propane. Triphenylphosphine and tri(2-methyl)phenylphosphine, are preferable. The ligand compounds may be used singly, or two or more kinds thereof may be used in combination.

[0028] The catalyst system may also include a reducing agent. Examples of the reducing agent include iron, zinc, manganese, aluminum, magnesium, sodium, and calcium, zinc, magnesium, and manganese are preferable. These reducing agents can be more activated by allowing these reducing agents to contact with acids such as organic acids. [0029] Examples of the salt other than transition metal salts that is employable in the catalyst system of the present invention include sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide and sodium sulfate; potassium compounds such as potassium fluoride, potassium chloride, potassium bromide, potassium iodide and potassium sulfate; and ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide and tetraethylammonium sulfate. Of these, sodium bromide, sodium iodide, potassium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferred. These may be used singly, or two or more kinds thereof may be used in combination.

[0030] The polymerization is carried out preferably in the presence of a polymerization solvent. Examples of the polymerization solvent include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N,N- dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, y- butyrolactone and Y-butyrolactam. Tetrahydrofuran, N,N- dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred.

[0031] The polymerization reaction may be conducted in an atmosphere of an inert gas, such as nitrogen gas.

[0032] The polymerization is preferably carried out at a temperature from 0 to 200°C, more preferably 50 to 80° C. The polymerization time is typically 0.5 to 100 hours, preferably 1 to 40 hours.

[0033] After the completion of the polymerization reaction, Polymer (GP) can be isolated using known polymer isolation techniques. In an embodiment, Polymer (GP) is precipitated by mixing a solvent in which Polymer (GP) is poorly soluble with the reaction mixture.

[0034] Polymer (GP) precipitated from the reaction mixture is then separated by filtration. In an alternative embodiment, droplets of the reaction mixture are dropped, for instance by means of a nozzle, in a precipitation bath containing a solvent in which Polymer (GP) is poorly soluble. The solid particles that form are the recovered from the bath by decantation, filtration or any other known technique. [0035] Examples of the solvent in which the Polymer (GP) is insoluble or poorly soluble include water, acetone, methanol, ethanol and acetonitrile. Water and acetone are preferable.

[0036] The precipitated polyarylene polymer may then be washed to remove any traces of the catalyst system, and other additives, and then dried.

[0037] The process of the invention comprises the steps of providing a Polymer (GP) as defined above and of heating Polymer (GP) to a temperature of 100 to 200°C to convert the sulfonic acid ester groups -SO2R¹ into sulfonic acid groups -SO3M, with M being H or a monovalent cation, preferably H. The conversion is achieved by thermal treatment in the absence of any chemical treatment, such as hydrolysis with an acid or an alkali or reaction with an alkaline halide.

[0038] The step of heating Polymer (GP) to a temperature of 100 to 200°C comprises holding the polyarylene polymer at a temperature in the 100 to 200°C range for a time sufficient to achieve the conversion of the sulfonic acid ester groups into sulfonic acid groups. The conversion is achieved by thermal treatment in the absence of any chemical treatment. The expression “chemical treatment” means hydrolysis with an acid or an alkali or reaction with an alkaline halide. The heating step is generally performed for a time of 0.1 to 20.0 hours, typically a time of 1 .0 to 15.0 hours, even 1.0 to 10.0 hours.

[0039] The completion of the conversion can be determined using conventional analytical means, such as ¹H NMR.

[0040] At the end of the process at least 90%, preferably at least 95%, of the sulfonic acid ester groups are converted into sulfonic acid groups.

[0041] Polymer (GP) may be in the form of a powder. The term “powder” is used herein to refer to a collection of solid particles with individual sizes.

[0042] Advantageously the solid particles of Polymer (GP) have an average size in the range of nanometers to millimeters, preferably from microns to millimeters. The average particle size can be in the range of 50 microns to 20 mm, from 100 microns to 10 mm or even from 200 microns to 5 mm.

[0043] Particle size may be determined according to any method known in the art. For instance particle size can be determined by laser diffraction on a suspension in isopropanol of the collection of the particles. A MicroTrac S3500 laser diffraction instrument can be used, according to the manufacturers’ instructions or known methods.

[0044] Powders may be heated to a temperature of 120 to 200 °C, more preferably from 140 to 160 °C.

[0045] Alternatively, Polymer (GP) may be dissolved in a solvent and then submitted to the heat treating step at a temperature of 100 to 200°C, preferably 100 to 160°C. More preferably Polymer (GP) can be heated in solution at a temperature of 130 to 160 °C, even more preferably at a temperature of 140 to 150 °C.

[0046] Suitable solvents are polar organic solvents. Suitable polar organic solvents are for instance selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methyl-2- pyrrolidone.

[0047] Alternatively, Polymer (GP) may be submitted to the heat treating step at the temperature of 100 to 200°C, preferably 130 to 160°C, before being isolated from the reaction mixture, at the end of the polymerization process. The heat treating step is performed in the absence of any acid, alkali or alkaline halide.

[0048] Polymer (GP), may be shaped in the form of a film or another article and then submitted to the heat treating step at a temperature of 100 to 200°C, preferably 120 to 200°C.

[0049] At the end of the process of converting the sulfonic acid ester groups of Polymer (GP) into sulfonic acid groups by heating, Polymer (GPA) is obtained, said polymer comprising recurring units of formula (AH): wherein R^x, R¹ and p are as defined above and M is H or an alkaline metal, preferably H. Polymer (GPA) may optionally comprise recurring units of formula (B) and/or (C) as defined above. [0050] Polymer (GPA) may be in the form of an alkaline metal salt, in particular sodium or potassium salt. Conversion of the sulfonic acid groups in Polymer (PA) into alkali metal sulfonate groups can be done by reaction with a suitable alkali metal base such as NaOH or KOH.

[0051] Polymers comprising sulfonic acid groups are generally used as ion exchange polymers. They are also used as proton conducting polymers.

[0052] The ion exchange capacity of the polyarylene polymer can be controlled by changing the type, the use ratio and the combination of recurring units in the polymer. Ion-exchange capacity (IEC) refers to the total number of active sites or functional groups in a polymer that are responsible for ion exchange. In the present specification the ion exchange capacity (IEC) is defined as the number of milligrams equivalents of ions that may be exchanged per gram of dry resin.

[0053] The molar amount of recurring units of formula (A) and optionally recurring units of formula (2) and/or (3) in Polymer (GP) are selected to provide a polyarylene polymer having sulfonic acid groups, that is Polymer (GPA), with an ion exchange capacity of 1 .00 to 5.50 meq/g, preferably 1 .50 to 4.50 meq/g, still more preferably 2.20 to 4.00 meq/g.

[0054] Polymer (GPA) because of its ion exchange capacity may conveniently be used for the preparation of proton conductive membranes for electrolyzers, redox flow batteries and for fuel cells, as well as solid electrolytes for display elements, various kinds of sensors, signal transmission media, solid capacitors and the like. It may also be used in the preparation of ion exchange membranes or devices.

[0055] Surprisingly, it has been found that Polymer (GP) may be more easily shaped into a film than Polymer (GPA). Even more surprisingly it has been found that the inventive process for converting Polymer (GP) into Polymer (GPA) can conveniently be applied to Polymer (GP) after it has been shaped, for instance after it has been shaped into a film.

[0056] Accordingly, a further object of the invention is an article comprising Polymer (GP). Preferably the article is in the form of a film. The film generally has a thickness of 5 to 300 pm, preferably 10 to 150 pm, even 15 to 100 pm. [0057] A process for converting the film comprising Polymer (GP) into a polymer electrolyte membrane comprising Polymer (GPA) is also an object of the invention. The expression “polymer electrolyte membrane” is used herein to refer to films of polymeric material characterized by ion exchange properties.

[0058] In a first embodiment, the process comprises the steps of: providing a film comprising Polymer (GP) and heating said film at a temperature in the range of 100 to 200°C to convert the sulfonic acid ester groups in Polymer (GP) into sulfonic acid groups.

[0059] Heating of the film of Polymer (GP) is typically performed at a temperature in the range from 140 to 160 °C. The heating step typically lasts for 1 .0 to 6.0 hours. The heating step can be conducted under vacuum or in the presence of superheated steam.

[0060] In an advantageous alternative embodiment, the process comprises preparing a solution of Polymer (GP) in a polar organic solvent, applying the solution on a substrate, and drying at a temperature in the range from 100 to 160 °C to obtain a film and at the same time convert the sulfonic acid ester groups in Polymer (GP) into sulfonic acid groups. Suitable polar organic solvents are for instance dimethyl sulfoxide, N,N- dimethylformamide, N,N-dimethylacetamide, or N-methyl-2-pyrrolidone.

[0061 ] It has surprisingly been found that the viscosity of the solutions comprising polymer (GP) is more suitable for use in the process of film casting than the viscosity of solutions comprising Polymer (GPA).

[0062] At the end of the process, Polymer (GP) has been fully converted into Polymer (GPA) and the film comprises Polymer (GPA).

[0063] In an alternative process for preparing an electrolyte membrane comprising Polymer (GPA), Polymer (GP) in the form of a powder is first submitted to a heat treatment step at a temperature in the range of 100 to 160°C to convert sulfonic acid ester groups into sulfonic acid groups, then it is shaped in the form of a film.

[0064] The polymer electrolyte membrane comprising polymer (GPA) or the film comprising Polymer (GP) can be produced by a process including the step of applying the liquid composition or solution prepared by mixing the polymer with e.g., a suitable solvent, on a substrate by a known coating method. Non-limiting examples of suitable coating methods are die coating, spray coating, knife coating, roll coating, slot die coating, spin coating and gravure coating.

[0065] Specifically, the composition is applied on a substrate, and the applied composition is dried to obtain a membrane, the resultant membrane being optionally peeled from the substrate. Thereby, the film or the electrolyte membrane of the present invention can be obtained.

[0066] The substrate is not particularly limited as long as being a substrate on which a common composition is applied, and for example, a substrate such as a plastic substrate and a metal substrate is used. Preferred is a substrate composed of a thermoplastic resin such as a polyethylene terephthalate (PET) film or polyimide (Kapton®) film or a steel belt.

[0067] The electrolyte membrane comprising Polymer (GPA) preferably has a dry membrane thickness of 10 to 100 pm, preferably 15 to 85 pm, more preferably 20 to 80 pm and even 20 to 70 pm.

[0068] The electrolyte membrane of the present invention may be a single-layer membrane, or may be a multi-layer laminated membrane.

[0069] In the case of a laminated membrane, the thickness of each layer is arbitrarily determined: for example, the thickness may be such that one layer is thickened whereas another layer is thin. Each layer may be identical or different from one another.

[0070] The electrolyte membrane is manufactured may comprise a reinforcement, such as a porous base material or a sheet-like fibrous material.

[0071 ] Examples of the process for producing the reinforced solid polymer electrolyte membrane include a method in which a porous base material or a sheet-like fibrous material is impregnated with a composition comprising the Polymer (GP); a method in which Polymer (GP) is applied on a porous base material or a sheet-like fibrous material; and a method in which a membrane is formed from the composition beforehand, and the membrane is superposed on a porous base material or a sheet-like fibrous material, and these are hot pressed.

[0072] The porous base material is preferably a material having a large number of pores or gaps penetrating in the thickness direction. Examples thereof include organic porous base materials composed of various kinds of resins, and inorganic porous base materials composed of glass, metal oxides such as alumina or metals themselves.

[0073] The porous base material is preferably an organic porous base material. Specifically, preferred is a base material composed of at least one selected from the group consisting of polyolefins such as polytetrafluoroethylene, high molecular weight polyethylene, crosslinked polyethylene, polyethylene and polypropylene, polyimide, polyacrylonitrile, polyamideimide, polyetherimide, polyphenylene sulfide, polybenzamidazole, polyethersulfone, polyetherketone.

[0074] The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the inventive concepts. In addition, although the present invention is described with reference to particular embodiments, those skilled in the art will recognized that changes can be made in form and detail without departing from the spirit and scope of the invention.

[0075] EXAMPLES

[0076] Molecular weight determination Method - GPC

[0077] Gel permeation chromatography (GPC) analyses were carried out using a Waters 2695 Separations Module and a Waters 2487 Dual Wavelength Absorbance detector with dimethylacetamide (0.1 M LiBr) as an eluent on two PLgel 5 urn minimixed - D columns (250 x 4.6 mm) and a PLgel 5um MiniMIX-D Guard (50 x 4.6 mm). An ultraviolet detector monitoring 270 nm was used to obtain the chromatogram. A flow rate of 0.3 ml I min and injection volume of 5 uL of a 0.2 w / v % solution in mobile phase was selected. Calibration was performed with 10 narrow molecular weight polystyrene standards (Peak molecular weight range: 371 ,000 to 580 g I mol). The number average molecular weight M_n and weight average molecular weight M_w were reported.

[0078] Conductivity

[0079] A Bekktech conductivity cell is used to measure in-plane proton conductivity with a linear voltage sweep method using Ivium Vertex One potentiostat. All measurements take place at 80 °C in water. Conductivity was calculated as inverse of resistivity according to the following equation: where L is the distance between electrodes, R is resistance, W is width of sample, and T is thickness of sample.

[0080] Ion Exchange Capacity

[0081 ] Ion exchange capacity was determined using ¹ H NMR (deuterated DMSO). The ratio of the integral from 7.8 - 8.2 ppm (3 H’s) and the integral from 6.75 - 7.8 ppm (8 H’s) is used to calculate the mol % of sulfonated comonomer. From this value, IEC is calculated.

[0082] Example 1 : Preparation of Polymer (GP-1)

[0083] To a 3-neck 250 mL round-bottom flask were added bis(triphenylphosphine)nickel chloride (1.316 g, 20.12 mmol), potassium iodide (2.004 g, 12.07 mmol), triphenylphosphine (3.167 g, 12.07 mmol), 2,5-dichlorobenzophenone (11.58 g, 46.13 mmol), 2,6-dichlorobenzonitrile (0.883 g, 5.13 mmol), activated zinc dust (9.867 g, 150.9 mmol), and anhydrous N-methylpyrrolidone (110 mL) in a nitrogen atmosphere. The mixture was heated to 70 °C and held at temperature for 30 min before the addition of neopentyl-3,5-dichlorobenzenesulfonate (14.67 g, 49.35 mmol) at 37% solids in N-methylpyrolidone (39.6 g). The mixture was then kept at 70 °C for 3 additional hours. The reaction media was diluted with N- methylpyrrolidone (65 mL) and mixture was filtered with Celite as a filter aid. The resulting reaction mixture was separated into three portions. One of the two portions was poured in methanol to coagulate the polymer and filtered. The resulting polymer was washed and filtered with methanol containing 5% HCI four times prior to washing and filtering with methanol four times. The isolated material was then dried under reduced pressure (40 kPa) at 80°C for 18 h, and afforded Polymer (GP-1 ) as a powder. The polymer was analysed by ¹H NMR.

[0084] Example 1a - Conversion of Polymer (GP-1) to Polymer (GPA-1) and further transformation into a film

[0085] A portion of the reaction solution obtained in Example 1 (113 g) was added to a 3-neck 250 mL round-bottom flask and heated to 150 °C for 3 h. The polymer was coagulated into water (2000 g) and filtered. The polymer was subsequently washed and then dried under reduced pressure (40 kPa) at 70°C for 18 h, and afforded 6.27 g (75.8% yield) of polymer GPA-1 as a brown powder. Complete conversion of the neopentyl sulfonate ester into - SO3H was evidenced by ¹ H NMR.

[0086] Polymer (GPA-1 ) (5 g) was subsequently dissolved in 55 g of N- methylpyrrolidone at 80 °C. A portion of the prepared solution was cast on a glass plate substrate using a doctor blade then dried at 150 °C under nitrogen for 18 h. The membrane was soaked five times with deionized water for 5 min each then allowed to dry at room temperature before measuring conductivity. Conductivity and IEC values are reported in Table 1.

[0087] Comparative Example 1 - Conversion of Polymer (GP-1) to Polymer (GPA-T) using LiBr

[0088] A second portion of the reaction solution (113 g) was added to a 3-neck 250 mL round-bottom flask with LiBr (7.5 g) and heated to 100 °C for 24 h. The resulting reaction mixture was very viscous. The polymer was coagulated into water (2000 g) and filtered. The polymer was subsequently washed 4 times with acetone, 7 times with aqueous 1 N sulfuric acid, and twice with water. The isolated material was then dried under reduced pressure (40 kPa) at 70°C for 18 h, and afforded 6.16 g (74.5% yield) of Polymer (GPA- T) as a brown powder. Conversion of the neopentyl sulfonate ester into - SO3H was evidenced by ¹ H NMR.

[0089] Polymer (GPA-T) was subsequently dissolved in 55 g of N- methylpyrrolidone at 80 °C. A portion of the prepared solution was cast on a glass plate substrate using a doctor blade then dried at 150 °C under nitrogen for 18h. The membrane was soaked five times with deionzied water for 5 min each then allowed to dry at room temperature before measuring conductivity. Conductivity and IEC values are reported in Table 1.

[0090] The ion exchange capacity (IEC) values measured in the films of Example 1 and Comparative Example 1 as well as their conductivity measured at 80°C are reported in Table 1 .

Table 1

[0091] The data in Table 1 show that it is possible to quantitatively convert the sulfonic acid ester groups of Polymer (GP) into ion conducting sulfonic acid groups solely by thermal treatment in the absence of any chemical treatment. The film obtained by casting of the solution also exhibits high conductivity.

Claims

1 . A process for converting sulfonic acid ester groups into sulfonic acid groups in a polyarylene polymer comprising recurring units of formula (A): in which R¹ is a C1 -C20 alkoxy group, optionally substituted, each R^x, independently of each other, is selected from the group consisting of a hydrogen atom, a fluorine atom, a C1 -C20 alkyl group, a C1 -C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1 -C20 alkyl group, the C1 -C20 alkoxy group, the C6- C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1 -C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R^xs exist the neighboring two R^xs may be bonded to form a ring, and p is 1 or 2, said process comprising heating the polyarylene polymer to a temperature of 100°C to 200°C.

2. The process of claim 1 wherein the polyarylene polymer further comprises recurring units of formula (B): in which each Ry, independently of each other, is selected from the group consisting of a fluorine atom, a C1 -C20 alkyl group, a C1 -C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1 -C20 alkyl group, the C1 -C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1 -C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R^ys exist the neighboring two R^ys may be bonded to form a ring, and q is an integer from 1 to 4.

3. The process of claim 1 or 2 wherein the polyarylene polymer further comprises recurring units of formula (C): in which R^z1 and R^z2, independently of each other, are selected from the group consisting of a fluorine atom, a C1 -C20 alkyl group, a C1 -C20 alkoxy group, a C6-C20 aryl group, a C6-C20 aryloxy group, a C2-C20 acyl group or a cyano group, and the C1 -C20 alkyl group, the C1 -C20 alkoxy group, the C6-C20 aryl group, the C6-C20 aryloxy group and the C2-C20 acyl group may be substituted with at least one substituent selected from the group consisting of a fluorine atom, a cyano group, a C1 -C20 alkoxy group, a C6-C20 aryl group and a C6-C20 aryloxy group, and when multiple R^Z1 and R^z2 exist the neighboring ones may be bonded to form a ring; r and s are independently of each other an integer from 1 to 4; and Z is selected from the group consisting of an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, 2,2 isopropylidene group, 2,2 hexafluoroisopropylidene group.

4. The process of any one of claims 1 to 3 wherein the amount of recurring units of formula (A) is from 0.1 to 90.0 mol% with respect to the total amount of recurring units in the polymer.

5. The process of any one of claims 1 to 4 wherein the polyarylene polymer comprising recurring units of formula (A), and optionally of formula (B) and/or (C), is in the form of a powder.

6. The process of claim 5 wherein the powder is a collection of solid particles with an average particle size in the range of 50 microns to 20 mm.

7. The process of claims 5 or 6 wherein the polyarylene polymer powder is heated to a temperature of 120 to 200°C, preferably 140 to 160°C.

8. The process of any one of claims 1 to 4 wherein the polyarylene polymer comprising recurring units of formula (A), and optionally of formula (B) and/or (C), is dissolved in a solvent and then submitted to the heat treating step at the temperature of 100 to 160°C, preferably 130 to 160°C.

9. The process of claim 7 which is performed in the absence of any acid, alkali or alkaline halide.

10. The process of claim 8 or 9 wherein the solvent is selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N- dimethylacetamide, or N-methyl-2-pyrrolidone.

11 . The process of any one of claims 1 to 10 wherein the step of heating the polyarylene polymer is performed for a time of 0.1 to 20.0 hours, preferably a time of 1 .0 to 15.0 hours, more preferably 1 .0 to 10.0 hours.