Polyarylene copolymer and polymer electrolyte membrane using the same

Abstract

The present invention provides a polyarylene copolymer that undergoes good polymerization even in polymerization systems using divalent nickel compounds as catalysts, has a high molecular weight and excellent film-forming properties, and a polymer electrolyte membrane using the same. [Solution] A polyarylene copolymer is provided, comprising repeating units having a 2,2'-bis(arylsulfonyl)-4,4'-biphenylene structure as units without ion exchange groups, and repeating units having ion exchange groups, comprising units derived from a 2,2'-disulfo-4,4'-biphenylene structure or a salt thereof. This allows for control of the arrangement of substituents at coupling-related positions, enabling high molecular weight and self-supporting film formation even in divalent nickel-based coupling polymerization.

Description

Technical Field

[0001] The present invention relates to a polyarylene copolymer, a polymer electrolyte membrane, and a monomer composition and a production method related thereto.

Background Art

[0002] As a material for various electrochemical devices such as fuel cells, water electrolysis, redox flow batteries, chlor-alkali processes, and other various electrolysis processes, fluorine-based ion exchange polymers represented by Nafion (registered trademark) are widely used. Among them, perfluorosulfonic acid-based polymers have high ion conductivity and chemical stability, and thus have been widely studied or put into practical use in the above various applications. However, these fluorine-based materials are generally expensive, and due to concerns about environmental persistence related to PFAS and the increasing interest in regulatory compliance, the demand for PFAS-free materials is growing. Therefore, the development of a hydrocarbon-based polymer electrolyte membrane that can replace Nafion is desired.

[0003] Under such circumstances, as hydrocarbon-based polymer electrolyte membranes, materials in which an ion exchange group is introduced into an aromatic polymer have been studied. While these are advantageous from the perspective of cost reduction compared to fluorine-based materials, when they have an electron-donating site such as an ether bond in the main chain, problems such as oxidative degradation starting from the site and deterioration of properties due to the elimination of the ion exchange group under high-temperature and strong-acid conditions may arise. On the other hand, a polyphenylene-type skeleton in which the main chain consists of direct bonds between aromatic rings is rigid and has excellent chemical stability, and is easy to suppress oxidative degradation derived from the main chain. Therefore, by appropriately designing the mode of introducing the ion exchange group, it is expected to achieve both ion conductivity and durability.

[0004] For example, Patent Document 1 proposes a polyarylene copolymer having a polyphenylene-type skeleton in which the main chain consists of bonds between aromatic rings, and comprising repeating units in which sulfonic acid groups are directly bonded to the aromatic rings of the main chain as hydrophilic units, and repeating units without ion exchange groups in which aromatic ring-based side chains are introduced via sulfonate groups as hydrophobic units, as well as a method for producing the same.

[0005] However, the bis(cyclooctadiene)nickel(0) used in the polymerization methods described in Examples 4 and 5 of Patent Document 1 is expensive, unstable, and difficult to handle. Furthermore, in those examples, the amount used is equivalent to or greater than the amount of halogen atoms in the dihalogenated monomer subjected to polymerization, which presents challenges in terms of economics.

[0006] Furthermore, while Patent Document 1 describes a polymerization method using a divalent nickel compound as a catalyst, this method is not specifically implemented in the examples. Moreover, when the present inventors attempted polymerization using a divalent nickel compound as a catalyst, they found that, for example, in a system using (2,5-dichlorophenyl)-phenylsulfone and 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl) as monomers, a copolymer with a sufficient molecular weight could not be obtained, and it was not suitable as a material for film formation. Furthermore, although Patent Document 1 broadly describes multiple structures as dihalosulfo compounds and dihalosulfonyl compounds, it does not specifically show that in coupling polymerization using a divalent nickel compound, the substitution position of the sulfonyl group or sulfo group or its protecting group on the halogen atom involved in coupling greatly affects the polymerization progress and the molecular weight of the resulting polymer. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2013-209459 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide monomer compositions that allow polymerization to proceed well in polymerization systems using divalent nickel compounds as catalysts, yielding copolymers with high molecular weight and excellent film-forming properties, particularly combinations of monomers in which both the hydrophobic monomer and the hydrophilic monomer have a 4,4'-dihalogenated biphenyl skeleton, as well as copolymers using said monomer compositions and methods for producing the same. [Means for solving the problem]

[0009] As a result of diligent research to solve the above problems, the present inventors have found that in coupling polymerization catalyzed by a divalent nickel compound, polymerization does not proceed easily when using a combination of monomers having a sulfonyl group or a sulfo group or its protecting group at the ortho position relative to the halogen atom involved in coupling. Furthermore, even when a monomer having a free acid of a sulfo group or a salt thereof is used as a hydrophilic monomer, a copolymer with a sufficient molecular weight cannot be obtained. In contrast, by combining monomers having a 4,4'-dihalogenated biphenyl skeleton as both the hydrophobic and hydrophilic monomers, and introducing an aromatic group having a sulfonyl group and an alkyl-protected sulfo group, respectively, at the 2,2' positions located meta to the halogen atom, we discovered that polymerization proceeds well even in coupling polymerization catalyzed by a divalent nickel compound, and copolymers with high molecular weight and excellent film-forming properties can be obtained, thus completing the present invention. Patent Document 1 generally describes numerous structures of dihalosulfo compounds and dihalosulfonyl compounds that can constitute polyarylene copolymers. However, the document does not specifically show that, in coupling polymerization using divalent nickel compounds, the substitution position of the sulfonyl group or sulfo group or its protecting group on the halogen atom involved in the coupling significantly affects the polymerization progress and the molecular weight of the resulting copolymer. Furthermore, it does not provide any selection guidelines that would enable high molecular weight and self-supporting film formation in divalent nickel systems by avoiding the ortho configuration for the halogen atom and by using a meta configuration for the substituent in both hydrophobic and hydrophilic monomers. [Effects of the Invention]

[0010] According to the present invention, polymerization proceeds well even in polymerization systems using divalent nickel compounds as catalysts, and polyarylene copolymers with high molecular weight and excellent film-forming properties can be obtained.

[0011] Furthermore, according to the present invention, by combining monomers having a specific 4,4'-dihalogenated biphenyl skeleton as both the hydrophobic monomer and the hydrophilic monomer, copolymers suitable for the formation of self-supporting membranes, and even polymer electrolyte membranes containing the same, can be provided. In addition, since divalent nickel compounds can be used, it is advantageous in terms of catalyst handling and manufacturing costs compared to the case where zero-valent nickel compounds are used. This effect is not simply due to changing either the hydrophobic or hydrophilic monomer, but is achieved by a specific combination in which inhibitory factors at the ortho position for the halogen atom involved in coupling are avoided in the design of both the hydrophobic and hydrophilic monomers. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and can be modified as appropriate without departing from its essence.

[0013] The hydrophobic monomer used in the present invention is preferably a 2,2'-bis(arylsulfonyl)-4,4'-dihalogenated biphenyl compound. The aryl group is preferably unsubstituted or substituted phenyl group. The substituted phenyl group is preferably a phenyl group having 1 to 5 alkyl groups having 1 to 20 carbon atoms, which may be the same or different, on a benzene ring. Examples of the aryl group include phenyl group, methylphenyl group, dimethylphenyl group, trimethylphenyl group, ethylphenyl group, propylphenyl group, butylphenyl group, hexylphenyl group, octylphenyl group, decylphenyl group, dodecylphenyl group, etc., with phenyl group or 2,4,6-trimethylphenyl group being more preferred. In such a 2,2'-bis(arylsulfonyl)-4,4'-dihalogenated biphenyl compound, the arylsulfonyl group at the 2,2' position is located at the meta position relative to the halogen atom at the 4,4' position involved in coupling, and there is no sulfonyl group at the ortho position relative to the halogen atom.

[0014] The hydrophilic monomer used in the present invention is preferably a 2,2'-disulfo-4,4'-dihalogenated biphenyl compound in which the sulfo group is protected by an alkyl group having 1 to 20 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, and a 2,2-dimethylpropyl group. Preferably, it is a branched alkyl group, and more preferably a 2,2-dimethylpropyl group. In such a 2,2'-disulfo-4,4'-dihalogenated biphenyl compound, the sulfo group or its protecting group at the 2,2' position is located at the meta position relative to the halogen atom at the 4,4' position involved in coupling, and there is no sulfo group or its protecting group at the ortho position relative to the halogen atom.

[0015] In this invention, hydrophilic monomers are used as alkyl protectors during polymerization, and sulfo-free acids or their salts are not used. In coupling polymerization catalyzed by divalent nickel compounds, if free acids or their salts are used as hydrophilic monomers, polymerization proceeds very slowly, and copolymers with sufficient molecular weight cannot be obtained.

[0016] The coupling polymerization described above can be carried out using a divalent nickel compound as a catalyst, and nickel halides are preferred as the divalent nickel compound.

[0017] In the coupling polymerization described above, when a divalent nickel compound is used as a catalyst, it is preferable to carry out the polymerization in the presence of a nitrogen-containing bidentate ligand. Examples of nitrogen-containing bidentate ligands include 2,2'-bipyridine, 1,10-phenanthroline, and N,N'-tetramethylethylenediamine, with 2,2'-bipyridine being the most preferred. The amount of nitrogen-containing bidentate ligand used can be 0.2 moles to 2 moles per mole of nickel compound, with 1 mole to 1.5 moles being preferred.

[0018] In the aforementioned coupling polymerization, it is preferable to use zinc in combination. Zinc is usually used in powder form. The amount used can be 1 mole to 10 moles per mole of nickel compound, with 2 moles to 5 moles being preferable.

[0019] The coupling polymerization described above is preferably carried out in the presence of a solvent. Examples of solvents include aprotic polar solvents such as dimethyl sulfoxide, N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. Such solvents may be used alone or in a mixture of two or more. The amount of solvent used can be, for example, 1 to 100 times the weight of the total monomer composition. Preferably, it can be 5 to 20 times the weight of the solvent.

[0020] The coupling polymerization is preferably carried out in an atmosphere of an inert gas such as nitrogen gas. In addition, since the protecting group of the sulfonic acid group dissociates under a high-temperature environment to liberate sulfonic acid, the reaction temperature of the polymerization is preferably set within a range where the protecting group does not dissociate. Examples of the reaction temperature of the polymerization include a range of 0°C to 120°C. Preferably, for example, a range of 20°C to 60°C can be mentioned. Examples of the polymerization time include a range of 0.5 hours to 48 hours.

[0021] The polymer obtained by the coupling polymerization is a precursor polymer having an alkyl protecting group derived from a hydrophilic monomer. The precursor polymer is then deprotected to remove the alkyl protecting group, resulting in a polyarylene copolymer having a structural unit derived from a 2,2'-disulfo-4,4'-biphenylene structural unit or a salt thereof.

[0022] The deprotection is preferably carried out in the presence of an acid. Hydrochloric acid or the like can be used as the acid. The deprotection reaction can be carried out by adding an acid to the polymer-containing solution obtained after the polymerization. Examples of the deprotection reaction temperature include a range of 50°C to 150°C, preferably 80°C to 130°C. Examples of the deprotection reaction time include a range of 1 hour to 30 hours, preferably 5 hours to 24 hours.

[0023] After the deprotection reaction, the target polyarylene copolymer can be precipitated by pouring the reaction solution into a poor solvent. Examples of the poor solvent include water, methanol, acetone, and the like. The precipitated polymer can be recovered by washing and then drying.

[0024] The polyarylene copolymer of the present invention can be formed into a film by appropriately dissolving it in a solvent, casting it onto a substrate, and drying. The obtained film can be adjusted to an acid type or a salt type as needed and used as a polymer electrolyte membrane.

Examples

[0025] The embodiments of the present invention will be described in more detail below with reference to examples. The present invention is not limited to the following embodiments, and it goes without saying that various forms are possible in terms of details. Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the disclosed technical means are also included within the technical scope of the present invention.

[0026] Each measurement was performed as follows:

[0027] (Measurement of molecular weight) The polymers described in the examples were analyzed by gel permeation chromatography (hereinafter abbreviated as GPC) (analytical conditions are as follows), and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in polystyrene equivalent were calculated from the analytical results. <Analysis conditions> Measuring device: HLC-8420GPC (manufactured by Tosoh Corporation) Column: TSK-GEL (manufactured by Tosoh Corporation) Column temperature: 40℃ Mobile phase: N,N-dimethylformamide containing lithium bromide (lithium bromide concentration: 10 mMol / dm3) Flow rate: 0.5mL / min Detection wavelength: 300nm

[0028] (Measurement of ion exchange capacity) As a measurement sample, 100 mg of the acid-treated film was cut out, dried under reduced pressure at 120°C, and the dry film weight (W) was measured. dry The following measurements were taken: These membranes were immersed in a saturated NaCl aqueous solution (60 mL) at room temperature for 24 hours to measure the ionic groups. + From the mold Na + The solution was converted to the specified form. The HCl contained in the resulting solution was then quantified using a TS-1700 potentiometric automatic titrator (manufactured by Hiranuma Sangyo Co., Ltd.) with a 0.1 M KOH ethanol solution, and the ion exchange capacity IEC value was calculated using the following formula. JPEG0007911728000001.jpg15109

[0029] [Synthesis Example 1] (2,5-dichlorophenyl)-phenylsulfone It was synthesized according to the procedure described in the examples of Japanese Patent No. 5701903 (TIFF0007911728000002.tif4135). [Synthesis Example 2] 2,2'-Bis(phenylsulfonyl)-4,4'-biphenylene It was synthesized according to the procedure described in Example 9 of Japanese Patent No. 5701903 (TIFF0007911728000003.tif6758). [Synthesis Example 3] (2,5-dichlorophenyl)-mesitylsulfone The synthesis was carried out by the same procedure as described in the example of Japanese Patent No. 5701903, except that benzene was replaced with mesitylene. 1 H NMR (80 MHz, CH2Cl2) δ 8.25 (d, J = 2.2 Hz, 1H), 7.52 (dd, J = 8.5, 2.2 Hz, 1H), 7.35 (d, J = 8.5 Hz, 1H), 6.96 (s, 2H) , 2.48 (s, 6H), 2.31 (s, 3H). [Synthesis Example 4] 2,2'-Bis(mesitylsulfonyl)-4,4'-biphenylene The synthesis was carried out by the same procedure as described in Example 9 of Japanese Patent No. 5701903, except that benzene was replaced with mesitylene. 1 H NMR (80 MHz, CH2Cl2) δ 7.57 (d, J = 2.1 Hz, 2H), 7.36 (dd, J = 8.3, 2.1 Hz, 2H), 7.05 (d, J = 8.3 Hz, 2H), 6.95 (s, 4H) , 2.34 (s, 18H). [Synthesis Example 5] 4,4'-Dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl) It was synthesized according to the procedure described in the examples of Japanese Patent No. 5742500 (TIFF0007911728000006.tif6758).

[0030] Furthermore, in Examples 1, 2, Comparative Example 1, and Comparative Example 2 below, the charging ratio of sulfonic acid group-containing monomers to other aromatic monomers was set so that the ratio of sulfonic acid groups to the total number of aromatic rings in the polymer was the same (33%), calculated based on the structure of the monomers used. Other conditions (reaction concentration, amount of catalyst used, reaction temperature, etc.) were kept the same.

[0031] [Example 1] In a reaction vessel whose internal gas was replaced with nitrogen gas, 0.91 g of anhydrous nickel chloride, 1.10 g of 2,2'-bipyridine, and 25 g of N-methylpyrrolidone were charged, and the mixture was stirred at 120°C for 1 hour to prepare a nickel complex suspension. In a separate reaction vessel purged with nitrogen, 2.58 g of 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl), 2.48 g of 2,2'-bis(phenylsulfonyl)-4,4'-biphenylene, 20 g of N-methylpyrrolidone, and 2.76 g of zinc powder were added, and the temperature was raised to 40°C. Then, 53 mg of methanesulfonic acid was added. The resulting mixed solution was stirred at 40°C for 3 hours, then cooled to 20°C to obtain a monomer solution. The nickel complex suspension was poured into the obtained monomer solution, and the resulting mixture was stirred at 20°C for 13 hours to carry out a polymerization reaction, yielding a black polymerization solution containing repeating units shown in the following formula and polymers containing repeating units shown in the following formula. When this solution was analyzed using GPC, the Mw value was found to be 233,000. Next, N-methylpyrrolidone was added to the obtained polymerization solution to adjust the volume to 100 g. Then, 100 g of methyl ethyl ketone, 100 g of toluene, and 60 g of 17.5% hydrochloric acid were added, and the mixture was stirred at 20°C. After standing for 10 minutes, the solution was separated, and the lower aqueous layer was separated to obtain 150 g of the organic layer containing the polymer. The obtained organic layer was concentrated under reduced pressure, and after removing the methyl ethyl ketone and toluene by distillation, N-methylpyrrolidone was added to obtain 100 g of the solution containing the polymer. 4g of 35% hydrochloric acid was added to this solution and reacted at 120°C for 18 hours. The resulting reaction solution is poured into 500 g of acetone, the precipitated solid is washed with acetone, and dried under reduced pressure to obtain the following formula. The repeating unit shown in TIFF0007911728000007.tif6754 and the following formula A polyarylene copolymer consisting of repeating units represented by TIFF0007911728000008.tif4254 was obtained. The obtained polyarylene copolymer was then dissolved in dimethyl sulfoxide to obtain a solution of approximately 20%. The obtained polyarylene copolymer solution was applied to a PET film and dried at 120°C for 1 hour to obtain a polymer electrolyte membrane. The resulting polymer electrolyte membrane had an IEC of 2.1 mMol / g, and the introduction rate of sulfonic acid groups to all aromatic rings was 26%.

[0032] [Example 2] In a reaction vessel whose internal gas was replaced with nitrogen gas, 0.91 g of anhydrous nickel chloride, 1.10 g of 2,2'-bipyridine, and 25 g of N-methylpyrrolidone were charged, and the mixture was stirred at 120°C for 1 hour to prepare a nickel complex suspension. In a separate reaction vessel purged with nitrogen, 2.58 g of 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl), 2.90 g of 2,2'-bis(mesitylsulfonyl)-4,4'-biphenylene, 20 g of N-methylpyrrolidone, and 2.76 g of zinc powder were added, and the temperature was raised to 40°C. Then, 53 mg of methanesulfonic acid was added. The resulting mixed solution was stirred at 40°C for 3 hours, then cooled to 20°C to obtain a monomer solution. The nickel complex suspension was poured into the obtained monomer solution, and the resulting mixture was stirred at 20°C for 13 hours to carry out a polymerization reaction, yielding a black polymerization solution containing repeating units shown in the following formula and polymers containing repeating units shown in the following formula. When this solution was analyzed using GPC, the Mw value was found to be 505,000. Next, N-methylpyrrolidone was added to the obtained polymerization solution to adjust the volume to 100 g. Then, 100 g of methyl ethyl ketone, 100 g of toluene, and 60 g of 17.5% hydrochloric acid were added, and the mixture was stirred at 20°C. After standing for 10 minutes, the solution was separated, and the lower aqueous layer was separated to obtain 150 g of the organic layer containing the polymer. The obtained organic layer was concentrated under reduced pressure, and after removing the methyl ethyl ketone and toluene by distillation, N-methylpyrrolidone was added to obtain 100 g of the solution containing the polymer. 4g of 35% hydrochloric acid was added to this solution and reacted at 120°C for 18 hours. The resulting reaction solution is poured into 500 g of acetone, the precipitated solid is washed with acetone, and dried under reduced pressure to obtain the following formula. The repeating unit shown in TIFF0007911728000009.tif8054 and the following formula A polyarylene copolymer consisting of repeating units represented by TIFF0007911728000010.tif4254 was obtained. The obtained polyarylene copolymer was then dissolved in dimethyl sulfoxide to obtain a solution of approximately 20%. The obtained polyarylene copolymer solution was applied to a PET film and dried at 120°C for 1 hour to obtain a polymer electrolyte membrane. The resulting polymer electrolyte membrane had an IEC of 2.1 mMol / g, and the introduction rate of sulfonic acid groups to all aromatic rings was 29%.

[0033] [Comparative Example 1] In a reaction vessel whose internal gas was replaced with nitrogen gas, 0.91 g of anhydrous nickel chloride, 1.10 g of 2,2'-bipyridine, and 25 g of N-methylpyrrolidone were charged, and the mixture was stirred at 120°C for 1 hour to prepare a nickel complex suspension. In a separate reaction vessel purged with nitrogen, 2.58 g of 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl), 2.83 g of (2,5-dichlorophenyl)-phenylsulfone, 20 g of N-methylpyrrolidone, and 2.76 g of zinc powder were added, and the temperature was raised to 40°C. Then, 53 mg of methanesulfonic acid was added. The resulting mixed solution was stirred at 40°C for 3 hours, then cooled to 20°C to obtain a monomer solution. The nickel complex suspension was poured into the obtained monomer solution, and the resulting mixture was stirred at 20°C for 13 hours to carry out a polymerization reaction, yielding a black polymerization solution containing repeating units shown in the following formula and polymers containing repeating units shown in the following formula. When this solution was analyzed using GPC, the Mw value was found to be 43,000. Next, N-methylpyrrolidone was added to the obtained polymerization solution to adjust the volume to 100 g. Then, 100 g of methyl ethyl ketone, 100 g of toluene, and 60 g of 17.5% hydrochloric acid were added, and the mixture was stirred at 20°C. After standing for 10 minutes, the solution was separated, and the lower aqueous layer was separated to obtain 150 g of the organic layer containing the polymer. The obtained organic layer was concentrated under reduced pressure, and after removing the methyl ethyl ketone and toluene by distillation, N-methylpyrrolidone was added to obtain 100 g of the solution containing the polymer. 4g of 35% hydrochloric acid was added to this solution and reacted at 120°C for 18 hours. The resulting reaction solution is poured into 500 g of acetone, the precipitated solid is washed with acetone, and dried under reduced pressure to obtain the following formula. The repeating unit shown in TIFF0007911728000011.tif4532 and the following formula A polyarylene copolymer consisting of repeating units represented by TIFF0007911728000012.tif4254 was obtained. The obtained polyarylene copolymer was then dissolved in dimethyl sulfoxide to obtain a solution of approximately 20%. The resulting polyarylene copolymer solution was applied to a PET film and dried at 120°C for 1 hour. However, the resulting polymer electrolyte membrane crumbled when peeled from the film and did not become a self-supporting membrane.

[0034] [Comparative Example 2] In a reaction vessel whose internal gas was replaced with nitrogen gas, 0.91 g of anhydrous nickel chloride, 1.10 g of 2,2'-bipyridine, and 25 g of N-methylpyrrolidone were charged, and the mixture was stirred at 120°C for 1 hour to prepare a nickel complex suspension. In a separate reaction vessel purged with nitrogen, 2.58 g of 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl), 3.25 g of (2,5-dichlorophenyl)-mesitylsulfone, 20 g of N-methylpyrrolidone, and 2.76 g of zinc powder were added, and the temperature was raised to 40°C. Then, 53 mg of methanesulfonic acid was added. The resulting mixed solution was stirred at 40°C for 3 hours, then cooled to 20°C to obtain a monomer solution. The nickel complex suspension was poured into the obtained monomer solution, and the resulting mixture was stirred at 20°C for 13 hours to carry out a polymerization reaction, yielding a black polymerization solution containing repeating units shown in the following formula and polymers containing repeating units shown in the following formula. When this solution was analyzed using GPC, the Mw value was found to be 6,000. Since the Mw value was less than 10,000, the deprotection process was not performed.

[0035] (Comparison of Examples and Comparative Examples) In Examples 1, 2, Comparative Example 1, and Comparative Example 2 described above, the ratio of sulfonic acid groups to the total number of aromatic rings in the polymer, calculated based on the structure of the monomer used, was kept the same (33%), and the reaction conditions such as reaction concentration, catalyst usage, and reaction temperature were also kept the same. Therefore, the differences in molecular weight and film-forming properties of the obtained polymers can be attributed primarily to differences in the monomer structure, including the substitution positions of sulfonyl groups or sulfo groups or their protecting groups on halogen atoms involved in coupling. In Example 1, a 2,2'-bis(phenylsulfonyl)-4,4'-dihalogenated biphenyl compound having a sulfonyl group at the meta position relative to the halogen atom involved in coupling was used as the hydrophobic monomer, and 4,4'-dichlorobiphenyl-2,2'-disulfonic acid di(2,2-dimethylpropyl) having a protective sulfo group at the meta position relative to the halogen atom involved in coupling was used as the hydrophilic monomer. As a result, a polymer with Mw = 233,000 was obtained, and a self-supporting polymer electrolyte membrane was successfully obtained. In Example 2, a 2,2'-bis(mesitylsulfonyl)-4,4'-dihalogenated biphenyl compound having a sulfonyl group at the meta position relative to the halogen atom involved in coupling was used as the hydrophobic monomer. As a result, a polymer with Mw = 505,000 was obtained, and a self-supporting polymer electrolyte membrane was successfully acquired. In contrast, in Comparative Example 1, when (2,5-dichlorophenyl)-phenylsulfone, which has a sulfonyl group in the ortho position relative to the halogen atom involved in coupling, was used as the hydrophobic monomer, the Mw remained at 43,000, and the resulting film did not become a self-supporting film. In Comparative Example 2, when (2,5-dichlorophenyl)-mesitylsulfone, which has a sulfonyl group in the ortho position relative to the halogen atom involved in coupling, was used as the hydrophobic monomer, the Mw remained at 6,000, and the deprotection process could not be carried out. From these results, it was confirmed that by combining monomers having a 4,4'-dihalogenated biphenyl skeleton as both hydrophobic and hydrophilic monomers, and having a sulfonyl group, a sulfo group, or a protecting group thereof at the 2,2' position (which is meta to the halogen atom involved in coupling), polymerization proceeds well even in divalent nickel-based coupling polymerization, and a polyarylene copolymer with high molecular weight and excellent film-forming properties can be obtained.

Claims

1. Formula (1) (In the formula, each of the Ar groups is independently either an unsubstituted or substituted phenyl group, and each substituted phenyl group has 1 to 5 alkyl groups having 1 to 20 carbon atoms, which may be the same or different, on the benzene ring.) A repeating unit that does not have an ion exchange group, represented by Formula (2) (In the formula, each of the multiple M's independently represents 1 / n equivalent of a hydrogen atom or an n-valent cation, where n is an integer of 1 or more.) A polymer electrolyte membrane comprising a polyarylene copolymer having repeating units having ion exchange groups represented by , and having a weight-average molecular weight (Mw) of 100,000 or more.

2. The polymer electrolyte membrane according to claim 1, wherein the weight-average molecular weight (Mw) of the polyarylene copolymer is 233,000 or more.

3. The polymer electrolyte membrane according to claim 1, wherein each of the plurality of Ar groups is independently an unsubstituted phenyl group or a 2,4,6-trimethylphenyl group.

4. The polymer electrolyte membrane according to claim 3, wherein all of the aforementioned Ar groups are unsubstituted phenyl groups.

5. The polymer electrolyte membrane according to claim 3, wherein all of the plurality of Ar groups are 2,4,6-trimethylphenyl groups.

6. The polymer electrolyte membrane according to claim 1, wherein the polyarylene copolymer comprises repeating units represented by formula (1) and repeating units represented by formula (2).

7. Formula (3) (In the formula, each of the Ar groups is independently an unsubstituted or substituted phenyl group, and each substituted phenyl group has 1 to 5 alkyl groups having 1 to 20 carbon atoms, which may be the same or different, on the benzene ring, and each of the X groups independently represents a halogen atom.) A 2,2'-bis(arylsulfonyl)-4,4'-dihalogenated biphenyl compound represented by, Formula (4) (In the formula, each R independently represents an alkyl group having 1 to 20 carbon atoms, and each X independently represents a halogen atom.) A method for producing a polyarylene copolymer having a weight-average molecular weight (Mw) of 100,000 or more, comprising coupling polymerization of a monomer composition containing a 4,4'-dihalogenated biphenyl-2,2'-disulfonic acid dialkyl ester represented by in the presence of a divalent nickel compound, a nitrogen-containing bidentate ligand, and zinc, and deprotecting the sulfo protecting group of the obtained precursor polymer.

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