Electrolyte membrane and method for manufacturing the same, electrolyte membrane with catalyst layer, membrane electrode assembly, polymer electrolyte fuel cell, and polymer electrolyte water electrolysis device.

Abstract

An electrolyte membrane comprising a crosslinked polymer having a structure represented by formula (1), wherein the crosslinked polymer has a crosslinking group directly bonded to an aromatic hydrocarbon ring in the polymer unit. 【Chemical Formula 1】 JPEG0007838719000046.jpg16149[In formula (1), A 1 is a structural unit represented by formula (a1), A 2 is a structural unit represented by formula (a2), L 1 and L 2 are a single bond etc., n is an integer from 10 to 100, and * indicates a bond.] 【Chemical Formula 2】 JPEG0007838719000047.jpg42149[In formula (a1), IExG is an ion-exchange group, L 3 is a single bond etc., x is an integer from 2 to 10, and * indicates a bond.] 【Chemical Formula 3】 JPEG0007838719000048.jpg16149[In formula (a2), Ar is an arylene group having no ion-exchange group, L 4 is a single bond etc., y is an integer from 3 to 20, and * indicates a bond.]

Description

[Technical Field]

[0001] This disclosure relates to an electrolyte membrane and a method for producing the same, an electrolyte membrane with a catalyst layer, a membrane electrode assembly, a polymer electrolyte fuel cell, and a polymer electrolyte water electrolysis device. [Background technology]

[0002] In recent years, fuel cells have been attracting attention as a highly energy-efficient new energy technology, driven by environmental concerns. Among them, polymer electrolyte fuel cells, which use polymer materials as electrolytes, are particularly noteworthy because they have a high maximum current density and operate at low temperatures, making them suitable as power sources for mobile devices such as automobiles and small-capacity power sources for portable electronic devices.

[0003] Fluorine-based polymers are known as polymers (electrolyte polymers) used in electrolytes for polymer electrolyte fuel cells and water electrolysis (see, for example, Patent Document 1). Although fluorine-based polymers are widely used in electrolyte applications due to their high proton conductivity and excellent swelling resistance, they have the problems of being expensive and having a large environmental impact.

[0004] For these reasons, the development of electrolyte polymers that do not use fluorine is also progressing. For example, Patent Document 2 discloses an invention relating to a polymer electrolyte membrane made of a block copolymer containing one or more segments (A1) containing ionic groups and one or more segments (A2) that do not contain ionic groups. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-204119 [Patent Document 2] International Publication No. 2013-031675 [Non-patent literature]

[0006] [Non-Patent Document 1] Young Moo Lee, et al., “Synthesis of Crosslinked Sulfonated Poly(phenylene sulfide sulfone nitrile) for Direct Methanol Fuel Cell Applications”, Macromol. Rapid Commun., 30, 2009, pp. 64-68. [Non-Patent Document 2] Matteo Gigli, et al., “Crosslinked sulfonated poly(phenylene sulfide sulfone) membranes for vanadium redox flow batteries”, Sustain. Mater. Technol.,28,2021,e00249. [Overview of the project] [Problems that the invention aims to solve]

[0007] However, polymer electrolyte membranes made of non-fluorinated polymers obtained by block copolymerization, as disclosed in Patent Document 2 above, do not necessarily possess sufficient proton conductivity.

[0008] One aspect of this disclosure aims to provide an electrolyte membrane having excellent proton conductivity. [Means for solving the problem]

[0009] The present invention is as described in the claims, and the present disclosure provides, in some respects, the following [1] to

[15] .

[0010] [1] Formula (1): [ka] [In formula (1), A 1 The following equation (a1): [Chemical formula] (In formula (a1), IExG represents an ion exchange group, L 3 represents a single bond, -O-, -S-, -SO2- or -CO-, x represents an integer from 2 to 10, * represents a bond. The plurality of IExG may be the same as or different from each other, The plurality of L 3 may be the same as or different from each other.) represents a structural unit represented by A 2 is the following formula (a2): [Chemical formula] (In formula (a), Ar represents an arylene group having no ion exchange group, L 4 represents a single bond, -O-, -S-, -SO2- or -CO-, y represents an integer from 3 to 20, * represents a bond. The plurality of Ar may be the same as or different from each other, The plurality of L 4 may be the same as or different from each other.) represents a structural unit represented by L 1 and L 2 each independently represents a single bond, -O-, -S- or -SO2-, n represents an integer from 10 to 100, * represents a bond. The plurality of A 1 may be the same as or different from each other, The plurality of A 2 may be the same as or different from each other, The plurality of L 1 may be the same as or different from each other, The plurality of L 2 may be the same as or different from each other. However, multiple A 1 The difference of x in equation (a1) is 3 or less. Multiple A 2 The difference in y in equation (a2) is within 5. It includes a crosslinked polymer having the structure represented by, The crosslinked body is an electrolyte membrane having a plurality of polymer units derived from the polymer and a crosslinking group that is directly bonded to an aromatic hydrocarbon ring in the polymer unit and crosslinks the plurality of polymer units with each other.

[0011] [2] The aforementioned crosslinking group is given by the following formula (c1): [ka] [In formula (c1), R 1 z is one of the following groups: an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. 1 It shows a +1 valent organic group, z 1 This represents an integer greater than or equal to 1. * indicates a bond. R 1 The organic group may have some of its carbon atoms replaced by at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms. The electrolyte membrane according to [1], having a group represented by .

[0012] [3] Said L 1 and the L 2 The electrolyte membrane according to [1] or [2], wherein each bond is independently single-bonded, -O-, or -S-.

[0013] [4] Said L 3 The electrolyte membrane is one of the following, wherein the bonds are single bonds or -SO2- bonds.

[0014] [5] The electrolyte membrane according to any one of [1] to [4], wherein the constituent unit represented by formula (a1) comprises at least one group selected from the group consisting of a sulfonic acid group, an alkyl sulfonic acid group, and a sulfonimide group, and salts thereof, as the ion exchange group.

[0015] [6] The electrolyte membrane according to any one of [1] to [5], wherein the constituent unit represented by formula (a2) comprises, as the arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group, which may have substituents.

[0016] [7] An electrolyte membrane as described in any of [1] to [6], having an ion exchange capacity of 1.0 to 4.0 mmol / g.

[0017] [8] An electrolyte membrane as described in any of [1] to [7], wherein the gel fraction calculated from the following formula (I) is between 1 and 100%. Gel fraction = (W2 / W1) × 100 ... (I) [In formula (I), W1 and W2 represent the mass of the electrolyte membrane before and after immersion in dimethyl sulfoxide at 25°C for 24 hours, respectively.]

[0018] [9] Formula (1): [ka] [In formula (1), A 1 The following equation (a1): [ka] (In formula (a1), IExG indicates an ion exchange group. L 3 This represents a single bond, -O-, -S-, -SO2-, or -CO-. x represents an integer between 2 and 10. * indicates a bond. Multiple IExGs may be identical or different from one another. Multiple L 3 They may be the same or different from each other. The constituent units are shown, A 2 The following equation (a2): [ka] (In formula (a2), Ar represents an arylene group that does not have an ion exchange group. L 4 This represents a single bond, -O-, -S-, -SO2-, or -CO-. y represents an integer between 3 and 20. * indicates a bond. Multiple Ars may be identical or different from one another. Multiple L 4 They may be the same or different from each other. The constituent units are shown, L 1 and L 2 Each of these independently represents a single bond, -O-, -S-, or -SO2-. n represents an integer between 10 and 100. * indicates a bond. Multiple A 1 They may be the same or different from each other. Multiple A 2 They may be the same or different from each other. Multiple L 1 They may be the same or different from each other. Multiple L 2 They may be the same or different from one another. However, multiple A 1 The difference of x in equation (a1) is 3 or less. Multiple A 2 The difference in y in equation (a2) is within 5. A step of preparing an uncrosslinked film containing a polymer having a structure represented by and a crosslinking agent, A method for producing an electrolyte membrane, comprising the step of crosslinking the polymer with the crosslinking agent in a Friedel-Crafts reaction.

[0019]

[10] The aforementioned crosslinking agent is given by the following formula (2): [ka] [In formula (2), R 1 z is one of the following groups: an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. 1 It shows a +1 valent organic group, z 1 This represents an integer greater than or equal to 1. X 1 This represents a halogen atom or a hydroxyl group. R 1 The organic group may have some of its carbon atoms replaced by at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms. Multiple X 1 They may be the same or different from each other. A method for producing an electrolyte membrane according to [9], comprising at least one selected from the group consisting of a compound represented by and an intramolecular condensate of said compound.

[0020]

[11] The method for producing an electrolyte membrane according to [9] or

[10] , wherein the content of the crosslinking agent in the uncrosslinked membrane is 0.01 to 20 parts by mass per 100 parts by mass of the polymer.

[0021]

[12] An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of [1] to [8], and a catalyst layer disposed on one or both sides of the electrolyte membrane.

[0022]

[13] A membrane electrode assembly comprising an electrolyte membrane as described in any of [1] to [8], and an electrode layer disposed on one or both sides of the electrolyte membrane.

[0023]

[14] A polymer electrolyte fuel cell comprising the membrane electrode assembly described in

[13] .

[0024]

[15] A polymer electrolyte water electrolyzer comprising the membrane electrode assembly described in

[13] . [Effects of the Invention]

[0025] According to one aspect of this disclosure, it is possible to provide an electrolyte membrane having excellent proton conductivity. [Modes for carrying out the invention]

[0026] The following describes exemplary embodiments of this disclosure. However, this disclosure is not limited to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, each configuration and parameter disclosed in this specification can be combined in any way, and the upper and lower limits described individually can be combined in any way.

[0027] <Electrolyte membrane> An electrolyte membrane of one embodiment (hereinafter also referred to as "electrolyte membrane (E)") includes a crosslinked polymer (hereinafter also referred to as "polymer (P)") having a structure represented by the following formula (1). The crosslinked polymer (L) has a plurality of polymer units (hereinafter also referred to as "polymer units (P')") derived from polymer (P), and a crosslinking group that is directly bonded to an aromatic hydrocarbon ring in the polymer units (P') and crosslinks the plurality of polymer units (P') to each other.

[0028] [ka]

[0029] In formula (1), A 1This is a constituent unit represented by the following formula (a1) (hereinafter referred to as "constituent unit A 1 It is also called ". ) indicates A 2 This is a constituent unit represented by the following formula (a2) (hereinafter referred to as "constituent unit A 2 It is also called ". ) indicates L 1 and L 2 Each of these independently represents a single bond, -O-, -S-, or -SO2-, n is an integer between 10 and 100, and * represents a bond. Multiple A 1 They may be the same or different from each other, and there may be multiple A 2 These may be the same or different from each other, and there may be multiple L 1 These may be the same or different from each other, and there may be multiple L 2 They may be the same or different from each other. However, multiple A 1 The difference of x in equation (a1) is 3 or less, and multiple A 2 The difference of y in equation (a2) is within 5.

[0030] [ka]

[0031] In formula (a1), IExG represents an ion exchange group, L 3 represents a single bond, -O-, -S-, -SO2-, or -CO-, x represents an integer from 2 to 10, and * represents a bond. Multiple IExGs may be identical or different from each other, and multiple L 3 They may be the same or different from one another.

[0032] [ka]

[0033] In formula (a2), Ar represents an arylene group that does not have an ion exchange group, and L 4 represents a single bond, -O-, -S-, -SO2-, or -CO-, y represents an integer from 3 to 20, and * represents a bond. Multiple Ars may be the same or different from each other, and multiple L 4They may be the same or different from one another.

[0034] The electrolyte membrane (E), containing a crosslinked material (L), exhibits excellent proton conductivity, and tends to show even better proton conductivity in high-humidity environments (e.g., humidity above 80% RH). The reason for this effect is not clear, but it is speculated that the polymer (P) contains multiple A 1 Since the difference of x in equation (a1) is within 3, multiple hydrophilic constituent units A 1 They are identical or have similar molecular sizes, and multiple A 2 Since the difference of y in equation (a2) is within 5, multiple hydrophobic constituent units A 2 These molecules are identical or have similar molecular sizes. In other words, polymer (P) is composed of multiple hydrophilic constituent units A that are identical or have similar molecular sizes. 1 (Hydrophilic part) and multiple hydrophobic constituent units A that are identical or have similar molecular sizes to each other. 2 The polymer has a structure in which hydrophobic regions are precisely arranged, and the ion exchange groups are arranged at approximately equal intervals. It is presumed that the ion exchange groups in the polymer unit self-assemble in a higher-order structure, inducing a microphase separation structure. This is presumed to result in the formation of good proton conduction paths within the crosslinked material (L), leading to excellent proton conductivity.

[0035] The proton conductivity of the electrolyte membrane (E) is, for example, 135 mS / cm or higher under conditions of 80°C and 100% relative humidity, and may be 150 mS / cm or higher, 170 mS / cm or higher, or 180 mS / cm or higher.

[0036] Furthermore, because the electrolyte membrane (E) contains a crosslinker (L), it tends to exhibit superior swelling resistance compared to a membrane made of polymer (P). For example, the volume swelling rate of the electrolyte membrane (E) measured by the method of the examples may be 110% or less, 100% or less, 90% or less, 80% or less, or 50% or less. The reason why the crosslinker (L) provides superior swelling resistance is not clear, but it is presumed that crosslinking makes the polymer network denser, suppressing the penetration of water into the polymer, and that the amount of water that can be contained inside the polymer decreases due to the reduction in free volume. In addition, there is no particular lower limit to the volume swelling rate of the electrolyte membrane (E), but it may be 5% or more, 10% or more, 15% or more, or 20% or more. The volume swelling rate of the electrolyte membrane (E) may be 5 to 110%, and may also be 10 to 100%, 15 to 100%, 20 to 90%, 20 to 80%, or 20 to 50%.

[0037] (Polymer(P)) The polymer (P) is represented by the above formula (1), and the constituent unit A 1 and constituent unit A 2 The linking group (L 1 or L 2 The structure has a continuous repeating structure (the structure in [ ] in formula (1)) via ). The number of repeats (n) of the structure is 10 to 100, and may be 15 or more, 20 or more, 80 or less, or 50 or less. When the number of repeats (n) is 15 or more, it tends to have excellent gas barrier properties, and when the number of repeats (n) is 50 or less, it tends to have excellent solubility in solvents and film-forming properties. From these viewpoints, the number of repeats (n) of the structure may be 15 to 80, or 20 to 50.

[0038] The polymer (P) forms a crosslinked product (L) by, for example, a Friedel-Crafts reaction with a crosslinking agent. This reaction is known in the art (for example, see Non-Patent Document 1 for the Friedel-Crafts acylation reaction and Non-Patent Document 2 for the Friedel-Crafts alkylation reaction). The specific conditions for this reaction may follow the conditions in the electrolyte membrane manufacturing method described later. When a crosslinked product (L) is formed by the Friedel-Crafts reaction, multiple L in the polymer (P) 1 , L 2 and L 4 At least one of these linking groups is preferably a single bond, -O-, or -S-. The carbon atoms of the arylene group adjacent to these linking groups (single bond, -O-, or -S-) (for example, the carbon atom located in the ortho position of the linking group) tend to have a high electron density and are prone to undergoing a Friedel-Crafts reaction (electrophilic substitution reaction) with a crosslinking agent (acylation agent or alkylating agent).

[0039] [Constituent Unit A] 1 ] Constituent unit A 1 This is an aromatic ring having an ion exchange group (IExG) linked to a linking group (L 3 It has a continuous structure via a ion exchange group. Here, an ion exchange group is a group that has the property of being able to exchange ions with other ions by releasing ions (e.g., cations), and is also called an ionic group. The ion exchange group can be any protonic acid group. Examples of ion exchange groups include sulfonic acid groups, alkyl sulfonic acid groups, perfluoroalkyl sulfonic acid groups, sulfonimide groups, phosphonic acid groups, phosphate groups and carboxyl groups, and their salts. As mentioned above, ion exchange groups include those that form salts with metal ions, etc.

[0040] Sulfonic acid groups and their salts are, for example, -SO3M 1 / q(M represents H or a metal (for example, at least one selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Al, Fe, Pt, Rh, Ru, Ir, and Pd), and q represents the valence of M (for example, an integer from 1 to 4).) The metal represented by M exists as an ion (cation), and -SO3 - It forms salt.

[0041] Alkyl sulfonic acid groups and their salts are, for example, -R 4 SO3M 1 / q It is represented as R 4 The carbon atom is an alkanediyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 12 (an integer). 4 Specific examples include, for instance, a methylene group, a butane-1,4-diyl group, and a hexane-1,6-diyl group. M and q are the same as above.

[0042] Sulfonimide groups and their salts include, for example, -SO2NM 1 / q SO2R 5 It is represented as R 5 R is an alkyl group, and from the viewpoint of obtaining better proton conductivity, its number of carbon atoms is preferably 1 to 6 (an integer). 5 Specific examples include methyl, ethyl, and propyl groups. M and q are the same as above.

[0043] Constituent unit A 1 From the viewpoint of obtaining better proton conductivity, it is preferable that the ion exchange group includes at least one group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, and sulfonimide groups, and salts thereof, and more preferably that it includes at least one group selected from the group consisting of sulfonic acid groups and salts thereof. Constituent unit A 1 If the constituent unit A contains a sulfonic acid group as an ion exchange group, in addition to the above effects, the sulfonic acid group functions as an acid catalyst, thus eliminating the need for an acid catalyst in the Friedel-Crafts reaction. From a similar viewpoint, constituent unit A 1It is more preferable that the majority of the plurality of ion exchange groups present therein are those in the above preferred embodiment, and the constitutional unit A 1 It is particularly preferable that all of the plurality of ion exchange groups present therein are those in the above preferred embodiment.

[0044] Constitutional unit A 1 From the viewpoint of obtaining more excellent proton conductivity, as the linking group (L 3 ), it is preferable to contain at least one group selected from the group consisting of -SO2- and -CO-, and more preferably to contain -SO2-. From the same viewpoint, the constitutional unit A 1 Among the plurality of linking groups (L 3 ) present therein, it is more preferable that the majority are those in the above preferred embodiment.

[0045] Constitutional unit A 1 The linking group (L 3 ) in is preferably a single bond or -SO2- from the viewpoints of improving proton conductivity and chemical durability.

[0046] The bonding position of the linking group (L 3 ) is not particularly limited, but from the viewpoints of obtaining more excellent proton conductivity and chemical durability, it is preferably located at the ortho position or meta position with respect to the ion exchange group. That is, the constitutional unit A 1 Preferably includes a 1,4-phenylene group having an ion exchange group.

[0047] Constitutional unit A 1 The repetition number (x) of the structure within [ ] in the formula (a1) in is preferably 2 to 8, more preferably 3 to 5, from the viewpoints of obtaining more excellent proton conductivity, having excellent heat and water resistance, and increasing the crosslinking degree of the crosslinked body.

[0048] Constitutional unit A 1From the viewpoint of obtaining superior proton conductivity, it is preferable that the structure includes at least one structure selected from the group consisting of the structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)"), the structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)"), and the structure represented by the following formula (a1-3) (hereinafter referred to as "structure (a1-3)").

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] In equations (a1-1), (a1-2), and (a1-3), IExG and * have the same meaning as described above. In equation (a1-3), L 31 x represents -O- or -S-. Multiple IExGs may be the same or different from each other. 1 x represents an integer between 2 and 10, and x in equation (a1-2) 2 x represents an integer between 2 and 5, and x in equation (a1-3) 3 This represents an integer between 1 and 2. However, the constituent unit A 1 If it includes two or more structures selected from the group consisting of structure (a1-1), structure (a1-2), and structure (a1-3), then x 1 , 2x 2 (2 and x 2 (product of) and 4x 3 (4 and x 3 The sum of the products of x is between 6 and 10. 1 From the viewpoint of obtaining better proton conductivity, excellent resistance to hot water, and increasing the degree of crosslinking of the crosslinked material, it is preferably 2 to 5, and more preferably 2 to 3. 2From the viewpoint of obtaining better proton conductivity, excellent resistance to hot water, and increasing the degree of crosslinking of the crosslinked material, it is preferably 2 to 3, and more preferably 2. 3 From the viewpoint of obtaining better proton conductivity, excellent resistance to hot water, and increasing the degree of crosslinking of the crosslinked material, it is preferably 1.

[0053] Constituent unit A 1 It may consist only of structure (a1-1), or it may include structure (a1-1) and structures other than structure (a1-1). In the latter case, structure (a1-1) and structures other than structure (a1-1) are linking groups (L 3 They may be connected by ). Similarly, constituent unit A 1 It may consist only of structure (a1-2), or it may include structure (a1-2) and structures other than structure (a1-2). In the latter case, structure (a1-2) and structures other than structure (a1-2) are linking groups (L 3 They may be connected by ). Similarly, constituent unit A 1 It may consist only of structure (a1-3), or it may include structure (a1-3) and structures other than structure (a1-3). In the latter case, structure (a1-3) and structures other than structure (a1-3) are linking groups (L 3 They may be connected by ).

[0054] Constituent unit A 1 This may be a constituent unit represented by any of the following formulas (A1-1) to (A1-4).

[0055] [ka]

[0056] IExG and * in equations (A1-1) to (A1-4), and L in equations (A1-2) to (A1-4). 3 This is synonymous with the above. Multiple IExG may be the same as or different from one another. Multiple L 3 They may be the same or different from one another.

[0057] Constituent unit A 1 From the viewpoint of obtaining better proton conductivity and excellent chemical durability, it is preferable that the constituent unit is one of those represented by formulas (A1-1) to (A1-4), and more preferably the constituent unit represented by formula (A1-2). In formula (A1-2), L 3 From the viewpoint of improving proton conductivity and chemical durability, it is preferable that the bond be a single bond.

[0058] Multiple constituent units A in equation (1) 1 At least one of them may be one of those exemplified above, and multiple constituent units A 1 The majority of these may be those exemplified above, and multiple constituent units A 1 All of these may be examples given above.

[0059] Multiple constituent units A in equation (1) 1 This is a range where the difference of x in equation (a1) is 3 or less, and there are two or more constituent units A 1 It may consist of multiple constituent units A. 1 From the viewpoint of obtaining better proton conductivity, the number of types is preferably three or less, and more preferably two or less.

[0060] Multiple constituent units A in equation (1) 1 The difference of x in equation (a1) is preferably as close to 0 as possible from the viewpoint of obtaining better proton conductivity, but may be within 2, within 1, or 0.

[0061] [Constituent Unit A] 2 ] Constituent unit A 2 In this case, the arylene group (Ar) which does not have an ion exchange group is linked to the L group. 4 It has a continuous structure via ).

[0062] The arylene group is a divalent aromatic hydrocarbon group and has a structure obtained by removing two hydrogen atoms from a monocyclic or condensed polycyclic aromatic hydrocarbon. The number of aromatic rings in the arylene group is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1, from the viewpoint of solubility in solvents, film-forming ability, and obtaining better proton conductivity. The arylene group may have substituents other than ion exchange groups. Examples of substituents include alkyl groups and aryl groups. The alkyl group may be at least one group selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups. An example of an aryl group is the phenyl group. When the arylene group has an aryl group as a substituent, the number of aromatic rings in the arylene group includes the number of aromatic rings in the substituent.

[0063] An unsubstituted arylene group may be at least one group selected from the group consisting of phenylene, naphthylene, fluorene, anthracylene, phenanthrylene, triphenylene, pyrenylene, and tetracenylene groups. A substituted arylene group may be at least one group selected from the group consisting of diphenylfluorene, methylphenylene, ethylphenylene, dimethylfluorene, diethylfluorene, dipropylfluorene, diisopropylfluorene, dibutylfluorene, dipentylfluorene, dihexylfluorene, diheptylfluorene, dioctylfluorene, dinonylfluorene, didecylfluorene, diundecylfluorene, and didodecylfluorene groups. Note that a fluorene group as an arylene group means a divalent fluorene group (for example, fluorene-2,7-diyl group).

[0064] Constituent unit A 2From the viewpoint of solubility in the solvent, film-forming properties, and the degree of crosslinking of the crosslinked material, it is preferable that the arylene group contains at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have substituents, and it is more preferable that the arylene group contains at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have an aryl group as a substituent. Constituent Unit A 2 From the viewpoint of further improving solubility in the solvent and film-forming properties, it is more preferable to contain a phenylene group, and even more preferable to contain a 1,4-phenylene group. From a similar viewpoint, constituent unit A 2 It is particularly preferable that the majority of the multiple arylene groups present in the constituent unit A are of the above preferred embodiment. 2 It is extremely preferable that all of the multiple arylene groups present are independently phenylene groups, naphthylene groups, or fluorene groups, which may each have substituents.

[0065] Constituent unit A 2 From the viewpoint of increasing the degree of crosslinking of the crosslinked body, the linking group (L 4 ) preferably contains at least one group selected from the group consisting of a single bond, -O-, or -S-, and more preferably contains -O- or -S-. From a similar viewpoint, constituent unit A 2 Multiple linking groups (L) present inside 4 It is even more preferable that the majority of these are of the above-described preferred embodiment.

[0066] Constituent unit A 2 From the viewpoint of having excellent solubility in solvents and film-forming properties, as well as excellent mechanical strength of the electrolyte membrane, the linking group (L 4 It is preferable that the group contains at least one group selected from the group consisting of a single bond, -SO2-, and -CO-, and more preferably contains -SO2- or -CO-.

[0067] Constituent unit A 2 The linking group inside (L 4From the viewpoint of increasing the degree of crosslinking of the crosslinked material, and from the viewpoint of having excellent solubility in the solvent and film-forming properties, as well as excellent mechanical strength of the electrolyte membrane, the bond is preferably a single bond, -O-, -S-, or -SO2-, and more preferably a single bond, -O-, or -SO2-.

[0068] Constituent unit A 2 In formula (a2), the number of repeating structures (y) in the brackets [ ] is preferably 4 to 12, more preferably 5 to 10, from the viewpoint of obtaining better proton conductivity, excellent resistance to hot water, and increasing the degree of crosslinking of the crosslinked body.

[0069] Constituent unit A 2 In equation (a2), the number of repeating structures (y) in the brackets [ ] is preferably 2 to 7 more than the number of repeating structures (x) in equation (a1) (x + (2 to 7)), from the viewpoint of achieving both superior proton conductivity and resistance to hot water, and from the viewpoint of increasing the degree of crosslinking of the crosslinked material.

[0070] Constituent unit A 2 The number of aromatic rings in the main chain is preferably 4 to 21, more preferably 5 to 13, and even more preferably 6 to 11, from the viewpoint of obtaining better proton conductivity.

[0071] Constituent unit A 2 From the viewpoint of having excellent solubility in solvents and film-forming properties, as well as excellent mechanical strength of the electrolyte membrane, it is preferable that the material includes at least one structure selected from the group consisting of the structure represented by the following formula (a2-1) and the structure represented by the following formula (a2-2).

[0072] [ka]

[0073] [ka]

[0074] In equations (a2-1) and (a2-2), Ar and * have the same meanings as described above. Multiple Ars may be the same or different from one another.

[0075] Constituent unit A including the above structure 2 A concrete example of this is the constituent unit represented by the following formula (A2-1).

[0076] [ka]

[0077] Ar, L in equation (A2-1) 4 And * are synonymous with the above, Q indicates the base of the structure represented by formula (a2-1) or formula (a2-2), and y 1 and y 2 Each of these independently represents an integer between 2 and 4. 1 and y 2 From the viewpoint of obtaining better proton conductivity, excellent resistance to hot water, and increasing the degree of crosslinking of the crosslinked body, it is preferably 2 to 3. The multiple Ars may be the same or different from each other, and the multiple L 4 They may be the same or different from one another.

[0078] Constituent unit A including the above structure 2 This can be any of the constituent units represented by the following formulas (A2-2) to (A2-7).

[0079] [ka]

[0080] The * in equations (A2-2) to (A2-7) has the same meaning as above. The R in equations (A2-4) and (A2-6) 3 R represents an alkyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 12 (an integer). 3 Specific examples include methyl, ethyl, propyl, hexyl, and dodecyl groups. In formulas (A2-4) and (A2-6), multiple R3 They may be the same or different from one another.

[0081] Multiple constituent units A in equation (1) 2 At least one of them may be one of those exemplified above, and multiple constituent units A 2 The majority of these may be those exemplified above, and multiple constituent units A 2 All of these may be examples given above.

[0082] Multiple constituent units A in equation (1) 2 This is a range where the difference of y in equation (a2) is 5 or less, and there are two or more constituent units A 2 It may be composed of these elements.

[0083] Multiple constituent units A in equation (1) 2 The difference of y in equation (a2) is preferably as close to 0 as possible from the viewpoint of obtaining better proton conductivity, and may be within 4, within 3, within 2, within 1, or 0.

[0084] Multiple constituent units A in equation (1) 2 The difference in the number of aromatic rings in the main chain in formula (a2) is preferable to be close to 0 from the viewpoint of obtaining better proton conductivity, and may be within 5, within 4, within 3, within 2, within 1, or 0. From a similar viewpoint, the multiple constituent units A in formula (1) 2 The difference in the number of aromatic rings in formula (a2) is preferably as close to 0 as possible, and may be 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or 0.

[0085] [Linking group] Polymer (P) is a constituent unit A, from the viewpoint of increasing the degree of crosslinking of the crosslinked material. 1 and constituent unit A 2 Linking group between (L 1 or L 2 It is preferable that the polymer (P) contains at least one group selected from the group consisting of a single bond, -O-, or -S-. From a similar viewpoint, multiple constituent units A in the polymer (P) 1 and constituent unit A 2 Linking group between (L1 and L 2 It is more preferable that the majority of these are of the above preferred embodiment, and that there are multiple constituent units A in the polymer (P). 1 and constituent unit A 2 Linking group between (L 1 and L 2 It is even more preferable that all of ) are of the above preferred embodiment. That is, L 1 and L 2 However, it is even more preferable that each bond be a single bond, -O-, or -S- independently.

[0086] The polymer (P) may consist of a structure represented by formula (1) and terminal structures bonded to the structure. The polymer (P) may be a compound represented by any of the following formulas (1-1) to (1-3).

[0087] [ka]

[0088] A in equations (1-1) to (1-3) 1 , A 2 , L 1 , L 2 And n are the same as above. However, in equations (1-1) and (1-2), Z 2 L that binds 2 This is a single bond. 1 and Z 2Each of these independently represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Examples of alkylborane groups include diethylborane, diciamilborane, dicyclohexylborane, and 9-borabicyclo[3.3.1]nonane. Examples of boronic acid ester groups include pinacol boronic acid ester, 1,3-propanediol boronic acid ester, biscyclohexyldiol boronic acid ester, neopentyl glycol boronic acid ester, and catechol boronic acid ester.

[0089] Polymer (P) may contain multiple polymer units (hereinafter also referred to as "polymer unit A") that include the structure represented by formula (1). For example, polymer (P) may contain three or more polymer units A and terminal crosslinking groups that bond to the terminal structures of three or more polymer units A. Note that polymer unit A may, for example, have terminal groups Z from any of the compounds represented by formulas (1-1) to (1-3) above. 1 and Z 2 The polymer may have a structure that excludes the specified group. The terminal crosslinking group may be a group derived from a known crosslinkable compound (e.g., decafluorobiphenyl). If the terminal crosslinking group has an aromatic ring, the terminal structure of polymer unit A may be bonded directly to the aromatic ring of the terminal crosslinking group, or via -O-, -S-, or -SO2-. The number of terminal crosslinking groups may be one or more. The multiple terminal crosslinking groups may be the same or different from one another.

[0090] From the viewpoint of obtaining better proton conductivity, the proportion of the structure represented by formula (1) in the entire polymer (P) is preferably 80% by mass or more. From a similar viewpoint, the proportion of the structure represented by formula (1) in the entire polymer (P) may be 85% by mass or more, or 90% by mass or more. The proportion of the structure represented by formula (1) in the entire polymer (P) may be less than 100% by mass. The proportion of the structure represented by formula (1) in the entire polymer (P) may be 80% by mass or more and less than 100% by mass, 85% by mass or more and less than 100% by mass, or 90% by mass or more and less than 100% by mass.

[0091] The polymer (P) may contain fluorine atoms, but the fluorine content in the polymer (P) is preferably 5% by mass or less, and it is preferable that the polymer (P) does not contain fluorine atoms (the fluorine content is below the detection limit).

[0092] The number-average molecular weight of the polymer (P) may be 20,000 or more, 25,000 or more, or 30,000 or more from the viewpoint of superior proton conductivity and superior mechanical strength of the electrolyte membrane, and may be 300,000 or less, 200,000 or less, or 150,000 or less from the viewpoint of superior solubility in the solvent and film formation. From these viewpoints, the number-average molecular weight of the polymer (P) may be 20,000 to 300,000, 25,000 to 200,000, or 30,000 to 150,000.

[0093] The weight-average molecular weight of polymer (P) may be 40,000 or more, 50,000 or more, 60,000 or more, or 100,000 or more from the viewpoint of superior proton conductivity and superior mechanical strength of the electrolyte membrane, and may be 500,000 or less, 300,000 or less, 200,000 or less, 120,000 or less, or 80,000 or less from the viewpoint of superior solubility in solvents and film formation. From these viewpoints, the weight-average molecular weight of polymer (P) may be 40,000 to 500,000, 50,000 to 300,000, 60,000 to 200,000, 60,000 to 120,000, 100,000 to 120,000, or 60,000 to 80,000.

[0094] The ratio of the weight-average molecular weight to the number-average molecular weight of the polymer (P) (polydispersity) may be 1.5 or higher, and may be 2.0 or higher, 2.5 or higher, or 2.8 or higher. When the polydispersity of the polymer (P) is 2.5 or higher, excellent swelling resistance tends to be obtained. From the viewpoint of solubility in the solvent, the polydispersity of the polymer (P) may be 20.0 or lower, and may be 15.0 or lower, 10.0 or lower, 5.0 or lower, or 2.5 or lower. The polydispersity of the polymer (P) may be 1.5 to 20.0, 2.0 to 20.0, 2.5 to 20.0, 2.5 to 15.0, 2.8 to 10.0, 1.5 to 5.0, or 1.5 to 2.5.

[0095] The number-average molecular weight and weight-average molecular weight of polymer (P) are measured by gel permeation chromatography (GPC) and are expressed as standard polyethylene glycol / oxide (PEG / PEO) equivalent values.

[0096] Polymer (P) can be obtained, for example, by reacting (polymerizing) a compound represented by the following formula (b1) (hereinafter also referred to as "compound (b1)") with a compound represented by the following formula (b2) (hereinafter also referred to as "compound (b2)"). That is, polymer (P) can be a polymer of compound (b1) and compound (b2).

[0097] [ka]

[0098] In formula (b1), A 1 This is synonymous with the above, Y 1b and Y 2b Each of these independently represents a halogen atom. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0099] [ka]

[0100] In formula (b2), A 2 This is synonymous with the above, Z 1b and Z 2b Each of these independently represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of halogen atoms, alkylborane groups, and boronic acid ester groups are given above, Z 1 and Z 2 These are the same examples as halogen atoms, alkylborane groups, and boronic acid ester groups represented by .

[0101] In the above method, constituent unit A 1 and constituent unit A 2 A structure in which these are arranged alternately (a repeating structure) can be formed throughout the entire polymer. Therefore, according to the above method, the number of repeats n in formula (1) can be easily set to 10 or more.

[0102] According to the above method, L in equation (1) 1 and L 2 A polymer (P) is obtained in which the bonds are -O-, -S-, or single bonds. Specifically, Z 1b and Z 2b If at least one of them is a hydroxyl group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the elements is -O-, Z 1b and Z 2b If at least one of them is a thiol group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the elements is -S-, Z 1b and Z 2b If at least one of them is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, then L in formula (1) 1 and L 2 A polymer (P) is obtained in which at least one of the bonds is a single bond.

[0103] In the above method, A is calculated within the range where the difference of x in equation (a1) is 3 or less. 1The method involves using multiple types of compounds (b1) with different structures, and ensuring that the difference in y in formula (a2) is within 5. 2 It is permissible to use multiple types of compounds (b2) with different structures. As for compound (b1), Y 1b and / or Y 2b Multiple types of compounds with different properties can be used. Similarly, as compound (b2), Z 1b and / or Z 2b Multiple types of compounds with different properties can be used.

[0104] Compound (b1) and compound (b2) can be reacted (polymerized) by, for example, an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0105] The solvent used in the reaction should be a good solvent for compound (b1), compound (b2), and polymer (P), and should allow for the high molecular weight of polymer (P) during polymerization. For example, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea are preferably used. These solvents may be used individually or as a mixture of two or more.

[0106] A base is used to enhance the nucleophilicity of compound (b2). The base is not particularly limited as long as it can deprotonate compound (b2). For example, alkali metal hydroxides and carbonates, alkaline earth metal hydroxides and carbonates, and organic bases such as amines can be used. The alkali metal may be lithium, sodium, potassium, rubidium, or cesium. The alkaline earth metal may be magnesium, calcium, strontium, or barium.

[0107] The reaction temperature in aromatic nucleophilic substitution reactions may be in the range of 25 to 350°C. From the viewpoint of excellent reaction rate, a reaction temperature of 60°C or higher is preferred, and 100°C or higher is more preferred. From the viewpoint of suppressing polymer decomposition, a reaction temperature of 300°C or lower is preferred, and 250°C or lower is more preferred. From these viewpoints, a reaction temperature of 60 to 300°C is preferred, and 100 to 250°C is more preferred.

[0108] Compound (b1) and compound (b2) can also be reacted (polymerized) by a cross-coupling reaction in a solvent in the presence of a catalyst. Examples of solvents that can be used in the reaction are the same as examples of solvents that can be used in the aromatic nucleophilic substitution reaction described above.

[0109] There are no particular restrictions on the catalyst as long as it can carry out the cross-coupling reaction, and conventionally known catalysts can be used. For coupling reactions between halogens, for example, copper catalysts, nickel catalysts, or palladium catalysts can be used. For coupling reactions between halogens and boronic acid groups, alkylborane groups, or boronic acid ester groups, for example, conventionally known catalysts used in the Suzuki-Miyaura coupling reaction (palladium catalysts, nickel catalysts, etc.) can be used.

[0110] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I) hexafluorophosphate.

[0111] The nickel catalyst may be, for example, bis(1,5-cyclooctadiene)nickel(0), dibromobis(triphenylphosphine)nickel(II), or [1,1'-bis(diphenylphosphino)ferrocene]dichloronickel(II).

[0112] The palladium catalyst may be, for example, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(triphenylphosphine)palladium(II) dichloride, or [1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II).

[0113] The reaction temperature in the cross-coupling reaction may be in the range of 0 to 350°C. From the viewpoint of improving the reaction rate, a reaction temperature of 30°C or higher is preferred, and 60°C or higher is more preferred. From the viewpoint of suppressing polymer decomposition, a reaction temperature of 300°C or lower is preferred, and 250°C or lower is more preferred. From these viewpoints, a reaction temperature of 60 to 300°C is preferred, and 100 to 250°C is more preferred.

[0114] In the aromatic nucleophilic substitution and cross-coupling reactions described above, it is preferable to remove water from the reaction system in order to increase the molecular weight of the polymer (P). The method of dehydration is not particularly limited, but examples include a method of azeotropic dehydration by coexisting an azeotropic solvent in the reaction system, a method of continuously removing the water from the reaction system by heating above the boiling point of water, and a method of coexisting a water-absorbing agent such as a molecular sieve. The azeotropic solvent is not particularly limited as long as it can remove water, and for example, at least one selected from the group consisting of benzene, toluene, cyclohexane, and xylene may be used.

[0115] The above aromatic nucleophilic substitution and cross-coupling reactions are preferably carried out under an inert atmosphere (for example, under a nitrogen or argon atmosphere). After the polymerization reaction is complete, the polymer can be recovered from the reaction solution and purified to obtain the desired polymer. Methods for recovering the polymer from the reaction solution include, for example, adding the reaction solution to a solvent in which the polymer has low solubility, allowing the polymer to precipitate and be recovered as a solid, and removing the solvent from the reaction solution by evaporation and recovering the polymer as a solid. Methods for purifying the polymer include, for example, washing in a solvent in which the polymer has low solubility and the by-product inorganic salts and residual monomer-derived compounds have high solubility, and washing using a Soxhlet extractor. The methods for recovering and purifying the polymer are not limited to these methods.

[0116] Polymer (P) can also be obtained by oxidizing a polymer having the structure represented by formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, polymer (P) is obtained from among polymers having the structure represented by formula (1), L 1 , L 2 , L 3 or L 4 It can be an oxide of a polymer containing a -S- (sulfide group) (hereinafter referred to as "sulfide-containing polymer").

[0117] Polymer (P) can also be obtained by reacting (polymerizing) a polymer of compound (b1) and compound (b2) or its oxide with a known crosslinkable compound (e.g., decafluorobiphenyl) having three or more groups that react with the terminal structure of the polymer or its oxide to form crosslinks. In other words, polymer (P) can be a reaction product of a polymer of compound (b1) and compound (b2) or its oxide with a crosslinkable compound. This method makes it possible to obtain polymer (P) having a polymer of compound (b1) and compound (b2) or its oxide as polymer units.

[0118] The polymer (P) may be obtained by a method that includes a step of protonating the ion exchange groups that form salts with metal ions. This step may involve immersing the polymer obtained by the method described above (for example, a polymer of compound (b1) and compound (b2) or an oxide thereof, or a reaction product of the polymer or oxide with a crosslinkable compound) in an acid (for example, hydrochloric acid) to protonate the ion exchange groups (for example, a salt of a sulfonic acid group). By washing and drying the compound (for example, a powder) after immersion, the metal ions of the polymer before immersion are replaced with protons, and a polymer (P) with protonated ion exchange groups is obtained.

[0119] (Crosslinked body (L)) The crosslinked body (L) is a crosslinked body of polymer (P), and has a plurality of polymer units (P') derived from polymer (P), and a crosslinking group that is directly bonded to the aromatic hydrocarbon ring in the polymer units (P') and crosslinks the plurality of polymer units (P') to each other.

[0120] The polymer unit (P') may have the same structure as the structure represented by formula (1) above, except that the hydrogen atom directly bonded to the aromatic hydrocarbon ring in the polymer (P) is replaced by a crosslinking group. Multiple polymer units (P') may be identical or different from one another.

[0121] [Bridging group] The crosslinking group may be a group formed by a Friedel-Crafts acylation reaction between the polymer (P) and a crosslinking agent (acylation agent), or it may be a group formed by a Friedel-Crafts alkylation reaction between the polymer (P) and a crosslinking agent (alkylating agent).

[0122] Examples of groups formed by the Friedel-Crafts acylation reaction include the group represented by the following formula (c1) (hereinafter also referred to as the "bridged group (c1)").

[0123] [ka]

[0124] In formula (c1), R 1 z is one of the following groups: an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. 1 It shows a +1 valent organic group, z 1 represents an integer greater than or equal to 1, and * represents a combination.

[0125] R 1 The organic group may have some of its carbon atoms replaced by at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms. For example, R 1 The organic group may have a divalent heterogroup. Examples of divalent heterogroups include -O-, -S-, and =O. Among these, R 1 When the organic group has an ether group (-O-), it tends to have higher swelling resistance.

[0126] R1 The number of carbon atoms in the aliphatic hydrocarbon group is, for example, 1 to 12, preferably 1 to 6, and more preferably 2 to 4, from the viewpoint of obtaining better proton conductivity. The aliphatic hydrocarbon group may be linear or branched. 1 The aromatic ring contained in the aromatic hydrocarbon group may be monocyclic or polycyclic.

[0127] R 1 From the viewpoint of improving swelling resistance, it is preferable that it contains an aromatic hydrocarbon group, and more preferably a benzene ring. 1 If it contains an aromatic hydrocarbon group, then R in formula (c1) 1 The group that attaches to it (carbonyl group) is R 1 It may be directly bonded to the aromatic ring inside.

[0128] R 1 From the viewpoint of obtaining better proton conductivity, it is preferable that the material contains an aliphatic hydrocarbon group, and more preferably that it contains an aliphatic hydrocarbon group in which some of the carbon atoms are replaced by oxygen atoms.

[0129] z 1 z is, for example, 1 to 11, and from the viewpoint of improving swelling resistance, it is preferably 1 to 2, and more preferably 1. 1 If R is 1, 1 From the viewpoint of obtaining better proton conductivity and better swelling resistance, it is preferable that it contains one or more arylene groups, and the formula is *-Ar 1 -*, or, formula:*-Ar 2 -L 5 -Ar 3 -*(where Ar 1 ~Ar 3 Each of these independently represents an arylene group, L 5 It is more preferable that the group is a single bond, -O-, -S- or -CO-, and * indicates a bond. Specific examples of arylene groups include phenylene, naphthylene, fluorene, anthracylene, phenanthrylene, triphenylene, pyrenylene, and tetrasenylene groups.

[0130] Specific examples of the crosslinking group (c1) include groups represented by the following formulas (C1-1) to (C1-6).

[0131]

Chemical formula

[0132] In formulas (C1-1) to (C1-6), * indicates a bond.

[0133] From the viewpoint of obtaining more excellent proton conductivity and more excellent swelling resistance, the crosslinking group (c1) is preferably any of the groups represented by formulas (C1-1) to (C1-6), more preferably any of the groups represented by formula (C1-2), formula (C1-5) or formula (C1-6), still more preferably the group represented by formula (C1-2) or formula (C1-6), and particularly preferably the group represented by formula (C1-6).

[0134] The crosslinking group (c1) contained in the crosslinked body (L) may be one kind or a plurality of kinds. At least one of the plurality of crosslinking groups (c1) in the crosslinked body (L) may be the one exemplified above, more than half of the plurality of crosslinking groups (c1) may be the one exemplified above, or all of the plurality of crosslinking groups (c1) may be the one exemplified above.

[0135] The crosslinking group (c1) may be formed by a method other than the Friedel-Crafts acylation reaction.

[0136] Examples of the group formed by the Friedel-Crafts alkylation reaction include a group represented by the following formula (c2) (hereinafter, also referred to as "crosslinking group (c2)").

[0137]

Chemical formula

[0138] [[ID=4l]] In formula (c2), R 1This is synonymous with the above, R 2 z represents a hydrogen atom or a methyl group. 2 represents an integer greater than or equal to 1, and * represents a combination. Multiple R 2 They may be the same or different from one another.

[0139] z 2 z is, for example, 1 to 11, and is preferably 1 from the viewpoint of obtaining better proton conductivity. 2 If R is 1, 1 From the viewpoint of obtaining better proton conductivity and better swelling resistance, it is preferable that it contains one or more arylene groups, and the formula is *-Ar 4 -*or formula:*-Ar 5 -L 6 -Ar 6 -*(where Ar 4 ~Ar 6 Each of these independently represents an arylene group, L 6 ) represents a single bond, -O-, -S-, or -CO-, and * represents a bond. ) is more preferable. Specific examples of the arylene group are the same as for the bridging group (c1).

[0140] Specific examples of the crosslinking group (c2) include the groups represented by the following formulas (C2-1) to (C2-4).

[0141] [ka]

[0142] In formulas (C2-1) to (C2-4), R 2 The above is synonymous, and * indicates a coupling.

[0143] The crosslinking group (c2) is preferably a group represented by formulas (C2-1) to (C2-4), and more preferably a group represented by formula (C2-1), from the viewpoint of obtaining better proton conductivity and better swelling resistance.

[0144] The crosslinking group (c2) may be formed by a method other than the Friedel-Crafts alkylation reaction.

[0145] The crosslinking group (c2) contained in the crosslinked body (L) may be of one kind or a plurality of kinds.

[0146] The crosslinked body (L) may have either the crosslinking group (c1) or the crosslinking group (c2) alone, or may have both of these. From the viewpoint of excellent swelling resistance, the crosslinked body (L) preferably has the crosslinking group (c1). Further, the crosslinked body (L) may further have a group other than the crosslinking group (c1) and the crosslinking group (c2).

[0147] The crosslinked body (L) may have a structure in which a plurality of polymer units (P’) are three-dimensionally crosslinked via a crosslinking group, or may have a structure in which another polymer unit (P’) is grafted to the main chain of the polymer unit (P’) via a crosslinking group.

[0148] The crosslinked body (L) may have a crosslinkable group. The crosslinkable group may be a crosslinkable group derived from a crosslinking agent described later. That is, in the crosslinked body (L), a part of the crosslinkable groups of the crosslinking agent may remain unreacted.

[0149] (Electrolyte membrane (E)) The electrolyte membrane (E) may consist only of the crosslinked body (L), or may contain components other than the crosslinked body (L). The components other than the crosslinked body (L) may be a polymer (P), a reaction product (un-crosslinked body) of the polymer (P) and the crosslinking agent, the crosslinking agent, a catalyst, a water-retaining inorganic substance, an additive such as a radical scavenger, etc. The catalyst may be a catalyst for a crosslinking reaction (for example, Friedel-Crafts reaction). Specific examples of the additive include water, silica, cerium oxide, and manganese oxide. These components may be used alone or in combination of a plurality of kinds.

[0150] The content of the crosslinked material (L) may be 1 to 100% by mass, 5 to 95% by mass, 10 to 90% by mass, or 20 to 70% by mass, from the viewpoint of superior proton conductivity and swelling resistance. The above content is based on the total amount of solids in the electrolyte membrane (E).

[0151] The total content of polymer (P) and polymer (P)-derived components in the electrolyte membrane (E) may be 90-100% by mass, 94-100% by mass, or 97-100% by mass, from the viewpoint of superior proton conductivity and swelling resistance. Here, polymer (P)-derived components refer to the crosslinked material (L) and the reaction products (uncrosslinked material) of polymer (P) and the crosslinking agent. The above total content is based on the total solid content of the electrolyte membrane (E).

[0152] The ion exchange capacity (IEC) of the electrolyte membrane (E) may be 1.0 mmol / g or more, 1.5 mmol / g or more, 2.0 mmol / g or more, 2.2 mmol / g or more, or 2.4 mmol / g or more from the viewpoint of superior proton conductivity, and may be 4.0 mmol / g or less, 3.8 mmol / g or less, 3.5 mmol / g or less, 2.7 mmol / g or less, or 2.4 mmol / g or less from the viewpoint of superior swelling resistance. From these viewpoints, the ion exchange capacity of the electrolyte membrane (E) may be 1.0 to 4.0 mmol / g, 1.5 to 3.8 mmol / g, 2.0 to 3.5 mmol / g, 2.2 to 2.7 mmol / g, 2.4 to 2.7 mmol / g, or 2.2 to 2.4 mmol / g.

[0153] The ion exchange capacity of the electrolyte membrane is a value measured by the following procedure (1) to (4). (1) Dry the electrolyte membrane and determine its dry mass. Drying should be carried out until the mass loss when the electrolyte membrane is heated at 80°C is 1% by mass / hour or less. For example, after vacuum drying, heat at 80°C for 12 hours or more. (2) Immerse the dried electrolyte membrane in a 20% by mass sodium chloride aqueous solution and stir for 24 hours to perform ion exchange. (3) The point at which the pH becomes 7 is used as the endpoint, and the hydrochloric acid produced by the ion exchange described above is titrated with a 0.01 M sodium hydroxide aqueous solution. (4) The ion exchange capacity (IEC) of the electrolyte membrane is calculated using the following formula. IEC (unit: mmol / g) = {Concentration of sodium hydroxide solution (unit: mol / L) × Droplet volume (unit: mL)} / Dry mass of electrolyte membrane (unit: g)

[0154] The gel fraction in the electrolyte membrane (E) is preferably 1 to 100%. By setting the gel fraction to 1% or more, it becomes easier to obtain an electrolyte membrane with superior swelling resistance. Furthermore, a better phase separation structure is more easily formed, making it easier to obtain an electrolyte membrane with superior proton conductivity. From the above viewpoint, the gel fraction of the electrolyte membrane (E) may be 5% or more, 10% or more, 20% or more, or 40% or more. The gel fraction of the electrolyte membrane (E) may also be 95% or less, 90% or less, 70% or less, 30% or less, or 10% or less, and may be 5 to 95%, 10 to 90%, 20 to 70%, 40 to 70%, 1 to 70%, 1 to 30%, or 1 to 10%. The gel fraction of the electrolyte membrane (E) is determined as the insoluble fraction of the electrolyte membrane with respect to dimethyl sulfoxide. The specific calculation method is described in the examples below. In general, the gel fraction correlates with the degree of crosslinking of the electrolyte membrane. This is presumably because the more cross-linked portions there are in the electrolyte membrane, the lower the solubility in the solvent becomes, and the larger the amount of insoluble matter.

[0155] The gel fraction of the electrolyte membrane (E) is determined as the insoluble fraction of the electrolyte membrane relative to dimethyl sulfoxide (DMSO). Specifically, the electrolyte membrane is immersed in DMSO at 25°C for 24 hours and the value is calculated using the following formula (I). In formula (I), W1 and W2 represent the mass (in g) of the electrolyte membrane before and after immersion in DMSO at 25°C for 24 hours, respectively. Gel fraction = (W2 / W1) × 100 ... (I)

[0156] The thickness of the electrolyte membrane (E) is not particularly limited and can be changed according to the size of the fuel cell, etc. From the viewpoint of increasing the mechanical strength of the membrane while reducing membrane resistance, the thickness of the electrolyte membrane (E) may be, for example, 1 to 200 μm, or it may be 1 to 100 μm or 1 to 50 μm.

[0157] As described later, the electrolyte membrane (E) can be obtained by preparing a membrane containing a polymer (P) and a crosslinking agent (hereinafter also referred to as "uncrosslinked membrane (E')"), and crosslinking the polymer (P) in the uncrosslinked membrane (E') with the crosslinking agent (for example, the Friedel-Crafts reaction).

[0158] The electrolyte membrane (E) is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The electrolyte membrane (E) can also be used in redox flow batteries, electrochemical hydrogen pumps, chlor-alkali electrolyzers, solid acid catalysts, membrane-type humidity control devices, gas separation membranes, and the like.

[0159] The electrolyte membrane (E) can also be used in combination with a microporous membrane, nonwoven fabric, mesh, etc. That is, another embodiment of the present disclosure is a laminate comprising an electrolyte membrane (E) and another membrane (microporous membrane, nonwoven fabric, mesh, etc.).

[0160] <Method for manufacturing electrolyte membranes> One embodiment of the method for manufacturing an electrolyte membrane comprises a step of preparing a membrane (uncrosslinked membrane (E')) containing a polymer (P) and a crosslinking agent (hereinafter referred to as the "preparation step"), and a step of crosslinking the polymer (P) by reaction with the crosslinking agent (hereinafter referred to as the "crosslinking step"). This method yields an electrolyte membrane with excellent proton conductivity. Below, the method for manufacturing the electrolyte membrane of the above embodiment will be described using the case where the reaction in the crosslinking step is a Friedel-Crafts reaction as an example.

[0161] (preparation process) The uncrosslinked film (E') prepared in the preparation step contains a polymer (P) and a crosslinking agent. The crosslinking agent has at least two crosslinkable groups. Here, a crosslinkable group means a group that can react with the polymer (P) to form a crosslink. An example of a crosslinking agent is an acyling agent in the Friedel-Crafts reaction. Examples of acyling agents include compounds represented by the following formula (2) (hereinafter also referred to as "crosslinking agent (2)").

[0162] [ka]

[0163] In formula (2), R 1 and z 1 This is synonymous with the above, and X 1 X represents a halogen atom or a hydroxyl group. 1 These may be the same or different from each other. From the viewpoint of superior responsiveness, X 1 It is preferable that it is a hydroxyl group. From a similar viewpoint, all X 1 It is more preferable that it is a hydroxyl group.

[0164] The crosslinking agent (2) may be a compound represented by any of the following formulas (2-1) to (2-6).

[0165] [ka]

[0166] X in equations (2-1) to (2-6) 1 This is synonymous with the above.

[0167] The acylating agent may be an intramolecular condensate of the crosslinking agent (2). The intramolecular condensate of the crosslinking agent (2) is an acid anhydride obtained by an intramolecular dehydration reaction or an intramolecular dehalogenation reaction of the crosslinking agent (2), and has, for example, a structure represented by the following formula (2'). [ka]

[0168] In formula (2'), R 1 and X 1 This is synonymous with the above, and z 1a z represents an integer greater than or equal to 1, 1b This represents a non-negative integer. However, R 1 The valence is 2z 1a +z 1b That is the case.

[0169] As an acylation agent, it is preferable to use at least one selected from the group consisting of compounds represented by formulas (2-1) to (2-6) and their intramolecular condensates, from the viewpoint of making it easier to obtain an electrolyte membrane having better proton conductivity and better swelling resistance; more preferable to use at least one selected from the group consisting of compounds represented by formulas (2-2), (2-5), and (2-6) and their intramolecular condensates; even more preferable to use at least one selected from the group consisting of compounds represented by formulas (2-2) and (2-6) and their intramolecular condensates; and particularly preferable to use at least one selected from the group consisting of compounds represented by formula (2-6) and its intramolecular condensates.

[0170] The acylating agent may be used individually or in combination with other agents.

[0171] Another example of a crosslinking agent is an alkylating agent in the Friedel-Crafts reaction. Examples of alkylating agents include compounds represented by the following formula (3) (hereinafter also referred to as "crosslinking agent (3)").

[0172] [ka]

[0173] In formula (3), R 1 and z 2 This is synonymous with the above, and X 2 X represents a vinyl group, a monohalogenated methyl group, or a hydroxymethyl group. 2These may be the same or different from each other. From the viewpoint of obtaining higher reactivity, X 2 It is preferable that it is a monohalide methyl group. From a similar viewpoint, all X 2 It is more preferable that the group is a monohalogenated methyl group.

[0174] The crosslinking agent (3) may be a compound represented by any of the following formulas (3-1) to (3-4).

[0175] [ka]

[0176] X in equations (3-1) to (3-4) 2 This is synonymous with the above.

[0177] From the viewpoint of obtaining an electrolyte membrane with superior proton conductivity and superior swelling resistance, the alkylating agent is preferably one of the compounds represented by formulas (3-1) to (3-4), and more preferably the compound represented by formula (3-1).

[0178] Alkylating agents may be used individually or in combination of multiple types.

[0179] As the crosslinking agent, either the acyling agent or the alkylating agent may be used alone, or both may be used in combination. From the viewpoint of obtaining an electrolyte membrane with better swelling resistance, it is preferable that the crosslinking agent includes an acyling agent (i.e., the reaction in the crosslinking step includes a Friedel-Crafts acylation reaction).

[0180] The polymer (P) content in the uncrosslinked membrane (E') may be 60-100% by mass, 70-100% by mass, or 75-100% by mass, based on the total solid content of the uncrosslinked membrane (E'), from the viewpoint of obtaining an electrolyte membrane with superior proton conductivity.

[0181] From the viewpoint of making it easier to obtain an electrolyte membrane having better proton conductivity and better swelling resistance, the content of the crosslinking agent in the uncrosslinked membrane (E') may be 0.01 to 20 parts by mass per 100 parts by mass of polymer (P). From a similar viewpoint, the content of the crosslinking agent in the uncrosslinked membrane (E') may be 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 2 parts by mass or more, or 4 parts by mass or more per 100 parts by mass of polymer (P), and may also be 15 parts by mass or less, 10 parts by mass or less, 7 parts by mass or less, or 5 parts by mass or less, and may be 0.1 to 15 parts by mass, 0.3 to 10 parts by mass, 0.5 to 5 parts by mass, 2 to 10 parts by mass, or 4 to 7 parts by mass.

[0182] The uncrosslinked film (E') may consist only of the polymer (P) and the crosslinking agent, or it may contain other components besides the polymer (P) and the crosslinking agent. Examples of other components include the catalyst for the Friedel-Crafts reaction, the solvent remaining in the film, and the additives mentioned above. These other components may be used individually or in combination.

[0183] The catalyst is not particularly limited as long as it facilitates the Friedel-Crafts reaction, and conventionally known catalysts can be used. For the Friedel-Crafts acylation reaction, for example, iron(III) chloride, aluminum(III) chloride, zinc(II) chloride, boron trifluoride, sulfuric acid, trifluoroacetic acid, and polyphosphate can be used. For the Friedel-Crafts alkylation reaction, for example, iron(III) chloride, aluminum(III) chloride, zinc(II) chloride, boron trifluoride, sulfuric acid, trifluoroacetic acid, and polyphosphate can be used. The amount of catalyst used may be, for example, 0 to 200 parts by mass, 0 to 150 parts by mass, or 0 to 100 parts by mass per 100 parts by mass of crosslinking agent.

[0184] The ion exchange capacity of the uncrosslinked membrane (E') may be 1.0 mmol / g or more, 1.5 mmol / g or more, or 2.0 mmol / g or more, from the viewpoint of obtaining an electrolyte membrane with superior proton conductivity, and may be 4.0 mmol / g or less, 3.8 mmol / g or less, 3.5 mmol / g or less, 3.0 mmol / g or less, or 2.6 mmol / g or less, from the viewpoint of obtaining an electrolyte membrane with superior swelling resistance. From these viewpoints, the ion exchange capacity of the uncrosslinked membrane (E') may be 1.0 to 4.0 mmol / g, 1.5 to 3.8 mmol / g, 2.0 to 3.5 mmol / g, 2.0 to 3.0 mmol / g, or 2.0 to 2.6 mmol / g. The ion exchange capacity of the uncrosslinked membrane (E') described above is a value measured by the same method as the method for measuring the ion exchange capacity of the electrolyte membrane described above.

[0185] The preparation step may be a step of preparing a pre-formed uncrosslinked film (E'), or it may be a step of forming an uncrosslinked film (E') (hereinafter referred to as the "film formation step").

[0186] In the film formation step, an uncrosslinked film (E') may be formed by a known method for forming an electrolyte polymer film (e.g., solution casting method or dispersion casting method). Specifically, for example, an uncrosslinked film (E') may be formed on the substrate by applying a liquid composition containing a polymer (P) and a crosslinking agent to the substrate and then drying the liquid composition. The liquid composition may contain a Friedel-Crafts reaction catalyst and the additives mentioned above.

[0187] In the solution casting method, the solvent is not particularly limited as long as it can dissolve the polymer (P). For example, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea can be used. These can be used individually or in combination.

[0188] In the dispersion casting method, a dispersion medium capable of dispersing the polymer (P) is used. That is, the liquid composition contains a dispersion medium capable of dispersing the polymer (P). Examples of the dispersion medium include water, ethers, alcohols, ketones, esters, carboxylic acids, amines, acetonitrile, nitromethane, toluene, xylene, chlorobenzene, and chloroform. Examples of ethers include tetrahydrofuran and diethyl ether. Examples of alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol, and 1-butanol. Examples of ketones include acetone and cyclohexanone. Examples of esters include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methyl lactate, and ethyl lactate. Examples of carboxylic acids include formic acid, acetic acid, and propionic acid. Examples of amines include dimethylamine, diethylamine, triethylamine, pyridine, triethanolamine, and piperazine. These may be used individually or in combination.

[0189] The amount of solids other than the crosslinking agent and catalyst in the liquid composition (e.g., the amount of polymer (P)) may be 1 to 50% by mass, 2.5 to 40% by mass, or 5 to 30% by mass, based on the total amount of the liquid composition. The amount of crosslinking agent in the liquid composition may be 0.0001 to 10% by mass, 0.0025 to 6% by mass, or 0.025 to 3% by mass, based on the total amount of the liquid composition. The amount of Friedel-Crafts reaction catalyst in the liquid composition may be 0 to 20% by mass, 0 to 9% by mass, or 0 to 3% by mass, based on the total amount of the liquid composition.

[0190] The drying temperature and drying time for forming the uncrosslinked film (E') vary depending on the amount of liquid medium (solvent, dispersion medium) used, but the drying temperature may be, for example, 25-180°C, 40-150°C, or 55-120°C, and the drying time may be, for example, 0.05-72 hours, 0.1-48 hours, or 0.25-24 hours.

[0191] (Crosslinking process) In the crosslinking process, the polymer (P) in the uncrosslinked film (E') reacts with the crosslinking agent (an electrophilic reactant in the Friedel-Crafts reaction), causing the polymer (P) to crosslink and generate a crosslinked product (L). That is, if the reaction in the crosslinking process is a Friedel-Crafts reaction, the electrolyte film (E) of the above embodiment is obtained. The progress of crosslinking of the polymer (P) can be confirmed, for example, by a change (increase) in the gel fraction of the electrolyte film (E).

[0192] The reaction between the polymer (P) and the crosslinking agent may be carried out, for example, by heating the uncrosslinked film (E'). The heating temperature and heating time of the uncrosslinked film (E') may be changed according to the type of crosslinking agent used, the desired degree of crosslinking, etc. The heating temperature of the uncrosslinked film (E') may be, for example, 25 to 200°C, 40 to 190°C, or 55 to 180°C. The heating time of the uncrosslinked film (E') may be, for example, 0.05 to 72 hours, 1 to 48 hours, or 0.25 to 24 hours. The heating of the uncrosslinked film (E') may be carried out under vacuum conditions (e.g., 0.1 kPa or less), or in air.

[0193] In addition to the above steps, the method for manufacturing an electrolyte membrane according to one embodiment may also include a step of washing the membrane obtained in the crosslinking step (the membrane after the crosslinking reaction) (hereinafter referred to as the "washing step"). The washing step may be performed for purposes such as removing residual solvent, unreacted crosslinking agent, catalyst, by-products, etc. from the membrane, and neutralizing the pH.

[0194] In the washing step, the film after the crosslinking reaction may be washed using a washing solution. In this case, the electrolyte film is obtained by drying the film after the washing step using a method such as vacuum drying. As the washing solution, a known washing solution suitable for the purpose of washing may be used. Specific examples of washing solutions include hydrogen peroxide, sulfuric acid, hydrochloric acid, nitric acid, and pure water. These may be used individually or in combination of two or more.

[0195] <Electrolyte membrane with catalyst layer> An electrolyte membrane with a catalyst layer according to one embodiment comprises the electrolyte membrane of the above embodiment and a catalyst layer disposed on one or both sides of the electrolyte membrane.

[0196] The catalyst layer is, for example, a layer composed of an anode catalyst or a cathode catalyst, such as in a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. Hereinafter, a layer composed of an anode catalyst will be referred to as the anode catalyst layer, and a layer composed of a cathode catalyst will be referred to as the cathode catalyst layer.

[0197] The composition of the catalyst layer is not particularly limited and can be a conventionally known configuration for catalyst layers (anode catalyst layer, cathode catalyst layer) in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The catalyst layer may be formed of a conductive composition containing, for example, an anode catalyst or cathode catalyst and a conductive material. The catalyst layer may also contain an ionomer.

[0198] As an anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of fuels such as hydrogen can be used. As an anode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the oxygen evolution reaction can be used. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as alloys of two or more of these, can be used. These may be used individually or in mixtures of two or more.

[0199] As a cathode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the reduction reaction of oxygen can be used, and as a cathode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the hydrogen evolution reaction can be used. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as alloys of two or more of these, can be used. These may be used individually or in mixtures of two or more.

[0200] Examples of conductive materials that can be used include carbon blacks such as furnace black, Ketjen black, channel black, and acetylene black, activated carbon, and graphite. These may be used individually or in combination of two or more.

[0201] Conventional known materials can be used as the ionomer; for example, an ionomer containing a perfluoro electrolyte can be used. Alternatively, the above polymer (P) can be used as the ionomer. It is preferable to use a material with high oxygen permeability as the ionomer. There are no particular restrictions on the amount of ionomer added to the catalyst layer, but it is preferable to adjust the amount within a range where oxygen diffusion is not easily inhibited.

[0202] The catalyst layer may further contain additives such as water repellents like fluorinated carbon, binders like fluororesins and hydrocarbon resins having sulfonic acid groups.

[0203] A laminate comprising an electrolyte membrane with an anode catalyst layer and a cathode catalyst layer on both sides (for example, a laminate with a layer configuration of "anode catalyst layer / electrolyte membrane / cathode catalyst layer") is also called a CCM (Catalyst Coated Membrane) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0204] In the above embodiment, instead of the electrolyte membrane, a laminate comprising an electrolyte membrane and the other membranes mentioned above (microporous membrane, nonwoven fabric, mesh, etc.) can also be used.

[0205] <Membrane electrode assembly> One embodiment of the membrane electrode assembly comprises the electrolyte membrane of the above embodiment and an electrode layer disposed on one or both sides of the electrolyte membrane.

[0206] The electrode layer comprises, for example, the catalyst layer (anode catalyst layer or cathode catalyst layer) in the electrolyte membrane with catalyst layer of the above embodiment. Hereinafter, the electrode layer comprising the anode catalyst layer will be referred to as the anode layer, and the electrode layer comprising the cathode catalyst layer will be referred to as the cathode layer.

[0207] The configuration of the electrode layer is not particularly limited and may be a configuration conventionally known as the electrode layer (anode layer, cathode layer) of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. The electrode layer may consist, for example, of the catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion substrate. If the catalyst layer itself has gas diffusivity, the electrode layer may consist only of the catalyst layer. As the gas diffusion substrate, for example, a porous membrane can be used. As the gas diffusion substrate, in addition to gas diffusivity, materials that have water repellency and conductivity (for example, carbon fiber substrates such as carbon nonwoven fabric or carbon paper, or titanium fiber sintered bodies) can also be used.

[0208] A laminate comprising an electrolyte membrane with an anode layer and a cathode layer as electrode layers on both sides (for example, a laminate with a layer configuration of "gas diffusion substrate / anode catalyst layer / electrolyte membrane / cathode catalyst layer / gas diffusion substrate") is also called an MEA (Membrane Electrode Assembly) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0209] In the above embodiment, instead of the electrolyte membrane, a laminate comprising an electrolyte membrane and the other membranes mentioned above (microporous membrane, nonwoven fabric, mesh, etc.) can also be used.

[0210] <Polymer electrolyte fuel cell> A polymer electrolyte fuel cell according to one embodiment comprises the membrane electrode assembly of the above embodiment.

[0211] The configuration of a polymer electrolyte fuel cell is not particularly limited and may be a conventionally known configuration, except that it uses the membrane electrode assembly of the above embodiment. A polymer electrolyte fuel cell may, for example, comprise two or more membrane electrode assemblies. Two or more membrane electrode assemblies may be stacked (laminated) with a separator in between. A separator conventionally known for polymer electrolyte fuel cells can be used as the separator.

[0212] <Solid polymer water electrolysis device> One embodiment of a solid polymer water electrolysis apparatus includes the membrane electrode assembly of the above embodiment.

[0213] The configuration of the polymer electrolyte water electrolysis apparatus is not particularly limited, and can be a conventionally known configuration except for the use of the membrane electrode assembly of the above embodiment. The polymer electrolyte water electrolysis apparatus may, for example, further include a power supply element outside the membrane electrode assembly. It may also include two or more membrane electrode assemblies. [Examples]

[0214] The contents of this disclosure will be described in more detail below using examples and comparative examples, but this disclosure is not limited to the following examples.

[0215] <Synthesis Example 1> (Synthesis of hydrophilic monomer (M1)) A 10 L flask equipped with a dropping funnel, reflux condenser, and mechanical stirrer was purged with nitrogen, and 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of anhydrous tetrahydrofuran were charged in, and stirring was started. The mixture was cooled to -70°C in a methanol-dry ice bath, and 320 mL of 2.6 mol / L n-butyllithium-hexane solution was added dropwise. The mixture was stirred for 1 hour while remaining cooled in the bath. 40 mL of sulfur dioxide gas was introduced into the flask with nitrogen gas. The mixture was stirred for 30 minutes while remaining cooled in the bath. After that, the bath was removed and the temperature was raised to 0°C. The precipitated solid was filtered off by suction filtration and washed with 200 mL of tetrahydrofuran. The recovered solid was dissolved in 2 L of pure water, 260 mL of 35% hydrogen peroxide solution was added, and the mixture was stirred for 18 hours. The solid was removed by suction filtration, and 600 g of sodium chloride was added to the recovered filtrate. The precipitated white solid was collected by suction filtration and purified by recrystallization with water / isopropyl alcohol. The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer (M1) represented by the following formula (M1). The yield was 65%.

[0216] [ka]

[0217] <Synthesis Example 2> (Synthesis of hydrophobic monomer (M2)) In a 200 mL flask equipped with a stirring bar, Dean-Stark tube, reflux condenser, and calcium chloride tube, 4.0 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 14.8 g of [1,1'-biphenyl]-4,4'-diol, and 13.2 g of potassium carbonate were charged, and 50 mL of N,N-dimethylacetamide (DMAc) and 50 mL of toluene were added. The mixture was heated to 160°C in an oil bath while stirring, and heating and stirring continued for 4 hours. The toluene was removed from the Dean-Stark tube, and the mixture was heated to 180°C in an oil bath. After heating, heating and stirring continued for 8 hours. After the reaction mixture was allowed to cool to room temperature (approximately 25°C), the reaction mixture was poured into 200 mL of 10% hydrochloric acid, and the precipitated white solid was filtered off. The filtered solid was washed with 300 mL of ethanol and dried. The dried solid was purified by recrystallization from N-methylpyrrolidone (NMP) / ethanol. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0218] [ka]

[0219] <Synthesis Example 3> (Synthesis of hydrophobic monomer (M3)) A 500 mL flask equipped with a stirring bar and condenser was purged with nitrogen. To this flask, 9.5 g of 2,7-dibromo-9,9-diphenylfluorene, 12.1 g of 4'-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)biphenyl-4-ol, 19 g of potassium carbonate, 2.0 g of tetrakis(triphenylphosphine)palladium(0), and 250 mL of tetrahydrofuran were added. The reaction mixture was heated to 90°C and stirred for 3 hours. After the reaction mixture cooled to room temperature, 200 mL of water and 500 mL of ethyl acetate were added and the mixture was separated, and the organic layer was recovered. The solvent was removed by evaporation, and the resulting crude product was purified by silica column chromatography using an ethyl acetate / hexane = 1 / 1 (volume ratio) mixed solvent as the developing solvent. The fraction containing the target product was recovered, and the solvent was removed by evaporation. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M3) represented by the following formula (M3). The yield was 53%.

[0220] [ka]

[0221] <Synthesis Example 4> (Synthesis of polymer (P1)) In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 0.983 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.181 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.507 g of potassium carbonate were added, and the mixture was purged with nitrogen. Subsequently, 10 mL of dimethyl sulfoxide (DMSO) and 10 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube. Polymerization was carried out at 130 °C for 150 hours. After allowing the reaction mixture to cool to room temperature, reprecipitation purification was performed with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P1) having the structure represented by the following formula (P1). The yield was 97%. In formula (P1), n ​​was calculated from the number-average molecular weight described later.

[0222] [ka]

[0223] In equation (P1), M represents Na, K, or H, and n represents a positive number. In equation (P1), n ​​was approximately 20.

[0224] (molecular weight measurement) The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of polymer (P1) were measured under the following conditions, and the polydispersity (Mw / Mn) was determined. Mn was 30,000, Mw was 61,000, and Mw / Mn was 2.0.

[0225] [Measurement conditions] Polymer (P1) was dissolved at a concentration of 1 mg / mL in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L lithium bromide) to prepare the sample solution. A Tosoh HLC-8320GPC was used as the apparatus. Two Tosoh TSKgel SuperAWM-H columns (6.0 mm inner diameter, 15 cm length) were used. A differential refractometer was used as the detector. The flow rate was 0.6 mL / min and the temperature was 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined using standard polyethylene glycol / oxide (PEG / PEO) conversion. Furthermore, the polydispersity (Mw / Mn) was determined by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0226] (Protonation of polymers) The resulting polymer (P1) was immersed in 1M hydrochloric acid for 24 hours to remove metal ions (Na + or K + ) to proton (H + After substitution with ), the polymer (P1') was thoroughly washed by immersion in pure water and dried under reduced pressure to obtain a polymer in which the sulfonic acid salt was protonated.

[0227] <Synthesis Example 5> (Synthesis of polymer (P2)) In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 0.932 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, 1.297 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.593 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube. Polymerization was carried out by heating to 150 °C for 105 hours. After allowing the reaction mixture to cool to room temperature, reprecipitation purification was performed from 300 mL of IPA, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P2) having the structure represented by the following formula (P2). The yield was 90%. The Mn of polymer (P2), measured in the same manner as in Synthesis Example 4, was 51000, Mw was 110000, and Mw / Mn was 2.2.

[0228] [ka]

[0229] In equation (P2), M represents Na, K, or H, and n represents a positive number. The value of n in equation (P2) was approximately 30.

[0230] (Protonation of polymers) The resulting polymer (P2) was immersed in 1M hydrochloric acid for 24 hours to remove metal ions (Na + or K + ) to proton (H + After substitution with ), the polymer was thoroughly washed by immersion in pure water and dried under reduced pressure to obtain a polymer (P2') in which the sulfonic acid group salt was protonated.

[0231] <Comparative Example 1> In Comparative Example 1, a commercially available Nafion was used as the evaluation sample. TM Using NR211 (film thickness 25 μm), various measurements and evaluations (ion exchange capacity measurement, proton conductivity evaluation, and volume swelling rate measurement) were performed using the following methods.

[0232] (Ion exchange capacity measurement) The proton-substituted electrolyte membrane was dried at 80°C for 12 hours or more, and the dry mass was determined. The dried electrolyte membrane was immersed in a 20% sodium chloride aqueous solution and stirred for 24 hours to perform ion exchange. The resulting hydrochloric acid was titrated using a 0.01 M sodium hydroxide aqueous solution. An automatic titrator COM-A19 manufactured by HIRANUMA Corporation was used for the titration, and the endpoint was set at a pH of 7. The ion exchange capacity (IEC) was calculated using the following formula. The IEC for this comparative example was 1.00 mmol / g. IEC (unit: mmol / g) = {Concentration of sodium hydroxide solution (unit: mol / L) × Droplet volume (unit: mL)} / Dry mass of electrolyte membrane (unit: g)

[0233] (evaluation) [Proton conductivity evaluation] The proton conductivity of the obtained electrolyte membrane was measured by the following method. Using a Teflon® measurement cell (Scribner BT-115), the fabricated electrolyte membrane was placed in the cell in contact with four platinum wires. After maintaining the cell at 80°C and 20% relative humidity for 2 hours, the relative humidity was increased by 10% and maintained for 30 minutes. This procedure was repeated continuously until the relative humidity reached 100%, after which DC resistance was measured using the four-terminal method at 100% relative humidity. The proton conductivity in the planar direction of the electrolyte membrane was calculated from the obtained resistance value, the film thickness of the electrolyte membrane, and the distance between terminals. The proton conductivity of the electrolyte membrane in Comparative Example 1 under 80°C and 100% relative humidity was 129 mS / cm. Hereafter, the proton conductivity values ​​in the examples and comparative examples represent measurements taken under 80°C and 100% relative humidity. Note that in the following examples, the above-mentioned Nafion TM Using the proton conductivity of NR211 as a reference, an electrolyte membrane was evaluated as having excellent proton conductivity characteristics if its measured proton conductivity under conditions of 80°C and 100% relative humidity was 129 mS / cm or higher.

[0234] [Volume Swelling Rate Measurement] A 3 cm square membrane was punched out from the obtained electrolyte membrane, and the punched-out membrane was immersed in 50 mL of pure water at 80°C for 1 hour. The volume of the membrane was calculated by measuring its dimensions before and after immersion in pure water. The volume swelling rate was calculated by dividing the change in the volume of the membrane before and after immersion in pure water ([volume after pure water immersion] - [volume before pure water immersion]) by the volume of the membrane before immersion in pure water. The volume swelling rate was 61%.

[0235] <Example 1> (Fabrication of electrolyte membranes) The polymer (P1') obtained in Synthesis Example 4 and the crosslinking agent, 4,4'-dicarboxydiphenyl ether, were dissolved in DMAc to obtain a solution containing 10% by mass of polymer (P1') and 0.1% by mass of 4,4'-dicarboxydiphenyl ether. The obtained solution was cast onto a glass substrate and dried at 60°C for 20 hours to obtain the uncrosslinked film of Example 1 (film thickness 25 μm). The content of 4,4'-dicarboxydiphenyl ether in the uncrosslinked film was 1 part by mass per 100 parts by mass of polymer (P1'). The obtained uncrosslinked film was heated under vacuum conditions at 165°C for 10 hours, then washed sequentially with 10% sulfuric acid and pure water, and dried under reduced pressure to obtain the electrolyte film of Example 1 (film thickness 35 μm). The "film thickness" in this example was measured using PG-02 manufactured by TECLOCK CORPORATION. When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane in Example 1 was found to be 2.31 mmol / g.

[0236] (Gel fraction measurement) The obtained electrolyte membrane was immersed in DMSO at 25°C for 24 hours, and the gel fraction (%) was calculated using the following formula (I). The gel fraction of the electrolyte membrane in Example 1 was 25%, confirming that the polymer and crosslinking agent reacted to form crosslinks. Gel fraction = (W2 / W1) × 100 ... (I) In formula (I), W1 and W2 represent the mass (in g) of the electrolyte membrane before and after immersion in DMSO at 25°C for 24 hours, respectively.

[0237] (evaluation) The electrolyte membrane of Example 1 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 178 mS / cm, confirming that the electrolyte membrane of Example 1 has good proton conductivity. The volume swelling rate was 105%.

[0238] <Example 2> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) of Example 2 was obtained using the same method as in Example 1, except that the content of 4,4'-dicarboxydiphenyl ether in the uncrosslinked membrane was 3 parts by mass per 100 parts by mass of polymer (P1'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane of Example 2 was 2.32 mmol / g. The gel fraction of the electrolyte membrane of Example 2, calculated using the same method as in Example 1, was 64%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0239] (evaluation) The electrolyte membrane of Example 2 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 169 mS / cm, confirming that the electrolyte membrane of Example 2 has good proton conductivity. The volume swelling rate was 79%.

[0240] <Example 3> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 3 was obtained using the same method as in Example 1, except that the crosslinking agent was changed to adipic acid and the adipic acid content in the uncrosslinked membrane was set to 3 parts by mass per 100 parts by mass of polymer (P1'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 3 was 2.36 mmol / g. The gel fraction of the electrolyte membrane for Example 3, calculated using the same method as in Example 1, was 2%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0241] (evaluation) The electrolyte membrane of Example 3 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 184 mS / cm, confirming that the electrolyte membrane of Example 3 has good proton conductivity. The volume swelling rate was 93%.

[0242] <Example 4> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 4 was obtained using the same method as in Example 3, except that the adipic acid content in the uncrosslinked membrane was set to 5 parts by mass per 100 parts by mass of polymer (P1'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 4 was 2.44 mmol / g. The gel fraction of the electrolyte membrane for Example 4, calculated using the same method as in Example 1, was 5%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0243] (evaluation) The electrolyte membrane of Example 4 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 203 mS / cm, confirming that the electrolyte membrane of Example 4 has good proton conductivity. The volume swelling rate was 89%.

[0244] <Example 5> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 5 was obtained using the same method as in Example 1, except that the crosslinking agent was changed to diglycolic acid and the content of diglycolic acid in the uncrosslinked membrane was set to 3 parts by mass per 100 parts by mass of polymer (P1'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 5 was 2.24 mmol / g. The gel fraction of the electrolyte membrane for Example 5, calculated using the same method as in Example 1, was 1%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0245] (evaluation) The electrolyte membrane of Example 5 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 191 mS / cm, confirming that the electrolyte membrane of Example 5 has good proton conductivity. The volume swelling rate was 87%.

[0246] <Example 6> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 6 was obtained using the same method as in Example 5, except that the content of diglycolic acid in the uncrosslinked membrane was 5 parts by mass per 100 parts by mass of polymer (P1'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 6 was 2.17 mmol / g. The gel fraction of the electrolyte membrane for Example 6, calculated using the same method as in Example 1, was 54%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0247] (evaluation) The electrolyte membrane of Example 6 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 200 mS / cm, confirming that the electrolyte membrane of Example 6 has good proton conductivity. The volume swelling rate was 69%.

[0248] <Example 7> (Fabrication of electrolyte membranes) Except for changing the polymer to the polymer (P2') obtained in Synthesis Example 5 and setting the content of 4,4'-dicarboxydiphenyl ether in the uncrosslinked membrane to 1 part by mass per 100 parts by mass of polymer (P2'), the electrolyte membrane of Example 7 (thickness 35 μm) was obtained using the same method as in Example 1. When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane of Example 7 was 2.53 mmol / g. The gel fraction of the electrolyte membrane of Example 7, calculated using the same method as in Example 1, was 3%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0249] (evaluation) The electrolyte membrane of Example 7 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 155 mS / cm, confirming that the electrolyte membrane of Example 7 has good proton conductivity. The volume swelling rate was 46%, confirming that the electrolyte membrane of Example 7 has excellent swelling resistance.

[0250] <Example 8> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 8 was obtained using the same method as in Example 7, except that the content of 4,4'-dicarboxydiphenyl ether in the uncrosslinked membrane was 3 parts by mass per 100 parts by mass of polymer (P2'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 8 was 2.51 mmol / g. The gel fraction of the electrolyte membrane for Example 8, calculated using the same method as in Example 1, was 8%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0251] (evaluation) The electrolyte membrane of Example 8 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 166 mS / cm, confirming that the electrolyte membrane of Example 8 has good proton conductivity. The volume swelling rate was 47%, confirming that the electrolyte membrane of Example 8 has excellent swelling resistance.

[0252] <Example 9> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 9 was obtained using the same method as in Example 7, except that the content of 4,4'-dicarboxydiphenyl ether in the uncrosslinked membrane was 5 parts by mass per 100 parts by mass of polymer (P2'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 9 was 2.62 mmol / g. The gel fraction of the electrolyte membrane for Example 9, calculated using the same method as in Example 1, was 6%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0253] (evaluation) The electrolyte membrane of Example 9 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 179 mS / cm, confirming that the electrolyte membrane of Example 9 has good proton conductivity. The volume swelling rate was 43%, confirming that the electrolyte membrane of Example 9 has excellent swelling resistance.

[0254] <Example 10> (Fabrication of electrolyte membranes) An electrolyte membrane (thickness 35 μm) for Example 10 was obtained using the same method as in Example 7, except that the crosslinking agent was changed to diglycolic acid and the content of diglycolic acid in the uncrosslinked membrane was set to 3 parts by mass per 100 parts by mass of polymer (P2'). When the ion exchange capacity was measured using the same method as in Comparative Example 1, the IEC of the electrolyte membrane for Example 10 was 2.55 mmol / g. The gel fraction of the electrolyte membrane for Example 10, calculated using the same method as in Example 1, was 42%, confirming that the polymer and crosslinking agent reacted to form crosslinks.

[0255] (evaluation) The electrolyte membrane of Example 10 was evaluated using the same method as in Comparative Example 1 (proton conductivity evaluation and volume swelling rate measurement). The proton conductivity was 157 mS / cm, confirming that the electrolyte membrane of Example 10 has good proton conductivity. The volume swelling rate was 38%, confirming that the electrolyte membrane of Example 10 has excellent swelling resistance.

[0256] [Table 1]

[0257] This application is based on Japanese Patent Application No. 2024-169425, filed on 27 September 2024, which is incorporated by reference in its entirety. All references cited herein are incorporated as a whole.

Claims

1. The following formula (1): 【Chemistry 1】 [In formula (1), A １ The following formula (a1): 【Chemistry 2】 (In formula (a1), IExG indicates an ion exchange group. L ３ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, x represents an integer between 2 and 10. * indicates a coupling. Multiple IExGs may be identical or different from one another. Multiple L ３ (They may be the same or different from each other.) The constituent units are shown, A ２ The following formula (a2): 【Transformation 3】 (In formula (a2), Ar represents an arylene group that does not have an ion exchange group. L ４ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, y represents an integer between 3 and 20. * indicates a coupling. Multiple Ars may be identical or different from one another. Multiple L ４ (They may be the same or different from each other.) The constituent units are shown, L １ and L ２ each independently represents a single bond, -O-, -S- or -SO ２ - and indicates n represents an integer between 10 and 100. * indicates a coupling. Multiple A １ They may be the same or different from each other. Multiple A ２ They may be the same or different from each other. Multiple L １ They may be the same or different from each other. Multiple L ２ They may be the same or different from one another. However, multiple A １ The difference of x in equation (a1) is within 3, Multiple A ２ The difference in y in equation (a2) is within 5. It includes a crosslinked polymer having the structure represented by, The crosslinked body is an electrolyte membrane having a plurality of polymer units derived from the polymer and a crosslinking group that is directly bonded to an aromatic hydrocarbon ring in the polymer unit and crosslinks the plurality of polymer units with each other.

2. The aforementioned crosslinking base is given by the following formula (c1): 【Chemistry 4】 [In formula (c1), R １ z is one of the following groups: an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. １ It shows a +1 valent organic group, z １ This represents an integer greater than or equal to 1. * indicates a coupling. R １ The organic group may have some of its carbon atoms replaced by at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms. The electrolyte membrane according to claim 1, having a group represented by

3. Said L １ and L ２ The electrolyte membrane according to claim 1 or 2, wherein each of these is independently a single bond, -O-, or -S-.

4. Said L ３ However, single bonds or -SO ２ - The electrolyte membrane according to claim 1 or 2.

5. The electrolyte membrane according to claim 1 or 2, wherein the constituent unit represented by formula (a1) comprises at least one group selected from the group consisting of a sulfonic acid group, an alkyl sulfonic acid group, a sulfonimide group, and salts thereof, as the ion exchange group.

6. The electrolyte membrane according to claim 1 or 2, wherein the constituent unit represented by formula (a2) comprises, as the arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group, which may have substituents.

7. The electrolyte membrane according to claim 1 or 2, wherein the ion exchange capacity is 1.0 to 4.0 mmol / g.

8. The electrolyte membrane according to claim 1 or 2, wherein the gel fraction obtained from the following formula (I) is 1 to 100%. Gel fraction = (W ２ / W １ )×100...(I) [In formula (I), W １ and W ２ These values ​​represent the mass of the electrolyte membrane before and after immersion in dimethyl sulfoxide at 25°C for 24 hours, respectively.

9. The following formula (1): 【Transformation 5】 [In formula (1), A １ The following formula (a1): 【Transformation 6】 (In formula (a1), IExG indicates an ion exchange group. L ３ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, x represents an integer between 2 and 10. * indicates a coupling. Multiple IExGs may be identical or different from one another. Multiple L ３ (They may be the same or different from each other.) The constituent units are shown, A ２ The following formula (a2): 【Transformation 7】 (In formula (a2), Ar represents an arylene group that does not have an ion exchange group. L ４ These are single bonds, -O-, -S-, -SO ２ Show - or -CO-, y represents an integer between 3 and 20. * indicates a coupling. Multiple Ars may be identical or different from one another. Multiple L ４ (They may be the same or different from each other.) The constituent units are shown, L １ and L ２ These are, independently, a single bond, -O-, -S-, or -SO-. ２ - indicates, n represents an integer between 10 and 100. * indicates a coupling. Multiple A １ They may be the same or different from each other. Multiple A ２ They may be the same or different from each other. Multiple L １ They may be the same or different from each other. Multiple L ２ They may be the same or different from one another. However, multiple A １ The difference of x in equation (a1) is within 3, Multiple A ２ The difference in y in equation (a2) is within 5. A step of preparing an uncrosslinked film containing a polymer having a structure represented by and a crosslinking agent, A method for producing an electrolyte membrane, comprising the step of crosslinking the polymer with the crosslinking agent by a Friedel-Crafts reaction.

10. The aforementioned crosslinking agent is given by the following formula (2): 【Transformation 8】 [In formula (2), R １ z is one of the following groups: an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof. １ It shows a +1 valent organic group, z １ This represents an integer greater than or equal to 1. X １ This represents a halogen atom or a hydroxyl group. R １ The organic group may have some of its carbon atoms replaced by at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms. Multiple X １ They may be the same or different from each other. A method for producing an electrolyte membrane according to claim 9, comprising at least one selected from the group consisting of a compound represented by and an intramolecular condensate of said compound.

11. The method for producing an electrolyte membrane according to claim 9 or 10, wherein the content of the crosslinking agent in the uncrosslinked membrane is 0.01 to 20 parts by mass per 100 parts by mass of the polymer.

12. An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to claim 1 or 2, and a catalyst layer disposed on one or both sides of the electrolyte membrane.

13. A membrane electrode assembly comprising an electrolyte membrane according to claim 1 or 2, and an electrode layer disposed on one or both sides of the electrolyte membrane.

14. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 13.

15. A solid polymer water electrolysis apparatus comprising the membrane electrode assembly described in claim 13.

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