Polymer, electrolyte material, electrolyte membrane, electrolyte membrane with catalyst layer, membrane electrode assembly, solid polymer fuel cell, and solid polymer water electrolysis device

Abstract

This polymer has a structure represented by formula (1). [In formula (1), A1 represents a structural unit represented by formula (a1), A2 represents a structural unit represented by formula (a2), L1 and L2 each independently represent a single bond or the like, n represents an integer of 10-100, and * represents a binding hand.] [In formula (a1), IExG represents an ion exchange group, L3 represents a single bond or the like, x represents an integer of 2-10, and * represents a binding hand.] [In formula (a2), Ar represents an arylene group not having an ion exchange group, L4 represents a single bond or the like, y represents an integer of 3-20, and * represents a binding hand.]

Description

Polymers, electrolyte materials, electrolyte membranes, electrolyte membranes with catalyst layers, membrane electrode assemblies, solid polymer fuel cells, and solid polymer water electrolysis devices

[0001] The present disclosure relates to a polymer, an electrolyte material, an electrolyte membrane, an electrolyte membrane with a catalyst layer, a membrane electrode assembly, a polymer electrolyte fuel cell, and a polymer electrolyte water electrolysis device.

[0002] In recent years, fuel cells have been attracting attention as a new, highly energy-efficient energy technology against the backdrop of environmental issues. Among these, solid polymer fuel cells, which use polymer (high-molecular) materials as electrolytes, have attracted particular attention because they have a high maximum current density and operate at low temperatures, making them suitable for use as a mobile power source for automobiles and small-capacity power sources for portable electronic devices. Furthermore, from the perspective of carbon neutrality, the use of solid polymer hydrogen energy that applies fuel cell technology is also attracting attention.

[0003] Fluorine-based polymers are known as polymers (electrolyte polymers) used as electrolytes in polymer electrolyte fuel cells and water electrolysis (see, for example, Patent Document 1). Fluorine-based polymers are widely used in electrolyte applications due to their high proton conductivity, but they have problems such as high cost and a large environmental impact.

[0004] For these reasons, development of fluorine-free electrolyte polymers is also underway. 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 an ionic group and one or more segments (A2) not containing an ionic group.

[0005] Japanese Patent Application Laid-Open No. 11-204119 International Publication No. 2013-031675

[0006] However, the non-fluorinated polymer obtained by block copolymerization as disclosed in Patent Document 2 does not necessarily have sufficient proton conductivity.

[0007] An object of one aspect of the present disclosure is to provide a polymer that has excellent proton conductivity as an electrolyte.

[0008] In some aspects, the present disclosure provides the following [1] to

[16] .

[0009] [1] A polymer having a structure represented by the following formula (1): [In formula (1), A １ represents a structural unit represented by the following formula (a1), ２ represents a structural unit represented by the following formula (a2), and L １ and L ２ are each independently a single bond, —O—, —S— or —SO ２ -, n represents an integer of 10 to 100, * represents a bond. １ are identical to each other, and multiple A ２ are identical to each other, and multiple L １ may be the same or different, and multiple L ２ may be the same or different from each other. [In formula (a1), IExG represents an ion exchange group, and L ３ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, x represents an integer of 2 to 10, * represents a bond, a plurality of IExG may be the same or different, a plurality of L ３ may be the same or different from each other. [In formula (a2), Ar represents an arylene group having no ion exchange group, and L ４ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, y represents an integer of 3 to 20, * represents a bond, a plurality of Ar may be the same or different, a plurality of L ４ may be the same or different from each other.

[0010] [2] Said L １ , said L ２ , said L ３ and the L ４ are each independently a single bond or —SO ２ The polymer according to [1], wherein

[0011] [3] The polymer according to [1] or [2], wherein the structural unit represented by formula (a1) contains, as the ion exchange group, at least one selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group.

[0012] [4] The polymer according to any one of [1] to [3], wherein the constitutional unit represented by formula (a2) includes, as the arylene group, at least one selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group.

[0013] [5] The polymer according to any one of [1] to [4], having a number average molecular weight of 20,000 to 300,000.

[0014] [6] The polymer according to any one of [1] to [5], which is a polymer of a compound represented by the following formula (b1) and a compound represented by the following formula (b2), or an oxide thereof: [In formula (b1), A １ has the same meaning as above, and X １ｂ and X ２ｂ each independently represents a halogen atom. [In formula (b2), A ２ has the same meaning as above, and Z １ｂ and Z ２ｂ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

[0015] [7] The polymer according to any one of [1] to [6], which contains a plurality of polymer units containing the structure represented by formula (1) and has a crosslinking group bonding to three or more of the polymer units.

[0016] [8] The polymer according to [7], wherein the crosslinking group has one or more aromatic rings, and the polymer unit is bonded to the aromatic ring.

[0017] [9] The polymer according to [7] or [8], which is a reaction product of a polymer of a compound represented by the following formula (b1) and a compound represented by the following formula (b2), or an oxide thereof, and a compound having three or more groups that react with the polymer or the oxide thereof to form a crosslink: [In formula (b1), A１ has the same meaning as above, and X １ｂ and X ２ｂ each independently represents a halogen atom. [In formula (b2), A ２ has the same meaning as above, and Z １ｂ and Z ２ｂ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

[0018]

[10] The polymer according to any one of [1] to [9], wherein the ratio of the weight average molecular weight to the number average molecular weight is 2.0 to 20.0.

[0019]

[11] An electrolyte material containing the polymer according to any one of [1] to

[10] .

[0020]

[12] An electrolyte membrane containing the polymer according to any one of [1] to

[10] .

[0021]

[13] A catalyst layer-equipped electrolyte membrane comprising the electrolyte membrane according to

[12] and a catalyst layer disposed on one or both surfaces of the electrolyte membrane.

[0022]

[14] A membrane electrode assembly comprising the electrolyte membrane according to

[12] and electrode layers disposed on one or both surfaces of the electrolyte membrane.

[0023]

[15] A polymer electrolyte fuel cell comprising the membrane electrode assembly according to

[14] .

[0024]

[16] A polymer electrolyte water electrolysis device comprising the membrane electrode assembly according to

[14] .

[0025] According to one aspect of the present disclosure, a polymer having excellent proton conductivity as an electrolyte can be provided.

[0026] FIG. 1 is a graph showing the SAXS scattering intensity of the electrolyte membrane of Example 1.

[0027] Illustrative embodiments of the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. Furthermore, the upper and lower limit values ​​individually stated can be combined in any combination.

[0028] <Polymer> A polymer of one embodiment (hereinafter also referred to as "polymer (P)") has a structure represented by the following formula (1).

[0029]

[0030] In formula (1), A １ represents a structural unit represented by the following formula (a1) (hereinafter referred to as "structural unit A １ ") and A ２ is a structural unit represented by the following formula (a2) (hereinafter referred to as "structural unit A ２ ") and L １ and L ２ are each independently a single bond, —O—, —S— or —SO ２ -, n represents an integer of 10 to 100, and * represents a bond. １ are identical to each other, and multiple A ２ are identical to each other, and multiple L １ may be the same or different, and multiple L ２ may be the same or different from each other.

[0031]

[0032] In formula (a1), IExG represents an ion exchange group, L ３ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, x represents an integer of 2 to 10, and * represents a bond. ３ may be the same or different from each other.

[0033]

[0034] In formula (a2), Ar represents an arylene group having no ion exchange group, and L ４ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, y is an integer of 3 to 20, * is a bond. ４ may be the same or different from each other.

[0035] The polymer (P) is a so-called electrolyte polymer and has excellent proton conductivity. Therefore, a membrane (polymer electrolyte membrane) formed from the polymer (P) exhibits excellent proton conductivity. The reason why the polymer (P) has excellent proton conductivity is not clear, but it is thought that the polymer (P) has excellent proton conductivity when it is made up of a plurality of identical hydrophilic structural units A. １ (hydrophilic portion) and a plurality of identical hydrophobic structural units A ２ It is presumed that, since the structural unit A (hydrophobic portion) is precisely arranged, the ion exchange groups are arranged at equal intervals, and the ion exchange groups are self-assembled in a higher-order structure to induce a microphase-separated structure, which in turn forms a good proton conduction path within the polymer (P). １ The presence of three or more ion-exchange groups densely packed within the polymer also contributes to the improvement of phase separation and proton conductivity. The above effect is particularly pronounced in high-humidity environments (e.g., at humidity levels of 80% RH or higher).

[0036] The polymer (P) also tends to have excellent gas barrier properties when formed into a film. The reason for this is presumed to be as follows: Since the main chain of the polymer (P) is composed of an arylene group containing a benzene ring, the solubility of hydrogen and oxygen is low, and segment motion is restricted, thereby suppressing gas diffusion in the film, which is thought to result in excellent gas barrier properties when formed into a film.

[0037] (Polymer (P)) As represented by formula (1), the polymer (P) is a polymer having a structural unit A １ and structural unit A ２ and a linking group (L １ or L ２) between the repeating units (the structure in [ ] in formula (1)). The repeating number (n) of the structure is 10 to 100, and may be 15 or more or 20 or more, and may be 80 or less or 50 or less. When the repeating number (n) is 15 or more, the gas barrier property tends to be excellent, and when the repeating number (n) is 50 or less, the solubility in a solvent and the film-forming property tend to be excellent. The repeating number (n) of the structure is preferably 15 to 80, and more preferably 20 to 50.

[0038] [Structural unit A １ ] Structural unit A １ is an aromatic ring having an ion exchange group (IExG) and a linking group (L ３ ) and has a continuous structure.

[0039] Ion exchange groups, also called ionic groups, have the property of releasing ions (e.g., cations) to exchange with other ions. Examples of ion exchange groups include sulfone groups, alkylsulfone groups, perfluoroalkylsulfone groups, sulfonimide groups, phosphonic acid groups, phosphate groups, and carboxy groups. These ion exchange groups also include those in the form of salts. For example, a "sulfone group" is -SO ３ M １／ｑ (M represents H or a metal (e.g., Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Al, Fe, Pt, Rh, Ru, Ir, Pd), and q represents the valence of M (e.g., an integer of 1 to 4). The metal represented by M exists as an ion (cation), and is represented by -SO ３ － and forms salts.

[0040] The alkylsulfone group is, for example, —R １ SO ３ M １／ｑ It is expressed as: R １ is an alkanediyl group, the number of carbon atoms of which is preferably 1 to 12. １ Specific examples of include a methylene group, a butane-1,4-diyl group, and a hexane-1,6-diyl group. M and q are as defined above.

[0041] The sulfonimide group is, for example, —SO ２ NM １／ｑ SO ２ R ２ It is expressed as: R ２ is an alkyl group, the number of carbon atoms of which is preferably 1 to 6. ２ Specific examples of M include a methyl group, an ethyl group, and a propyl group. M and q are as defined above.

[0042] Structural unit A １ From the viewpoint of obtaining better proton conductivity, the structural unit A preferably contains, as an ion exchange group, at least one group selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group, and more preferably contains a sulfone group. １ It is more preferable that the majority of the ion exchange groups present in the structural unit A are those of the above-mentioned preferred embodiment. １ It is particularly preferred that all of the ion exchange groups present therein are of the above-mentioned preferred embodiment.

[0043] Structural unit A １ From the viewpoint of obtaining better proton conductivity, ３ ) as -SO ２ It is preferred that the group contains at least one group selected from the group consisting of — and —CO—, and ２ From the same viewpoint, it is more preferable that the structural unit A １ A plurality of linking groups (L ３ It is more preferable that the majority of the above-mentioned preferred embodiments.

[0044] Structural unit A １ The linking group (L ３ ) is preferably a single bond or —SO ２ It is preferable that −.

[0045] Linking group (L ３ The bonding position of the structural unit A) is not particularly limited, but it is preferably located at the ortho or meta position relative to the ion exchange group, and more preferably at the ortho position. １preferably contains a 1,4-phenylene group having an ion exchange group.

[0046] Structural unit A １ The number of repetitions (x) of the structure in brackets [ ] in formula (a1) in the above formula is preferably 2 to 8, and more preferably 3 to 5, from the viewpoints of obtaining better proton conductivity and excellent hot water resistance.

[0047] Structural unit A １ From the viewpoint of obtaining better proton conductivity, it is preferable that the polymerizable compound contains at least one structure selected from the group consisting of a structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)") and a structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)"):

[0048]

[0049]

[0050] IExG and * in formula (a1-1) and formula (a1-2) have the same meanings as above. Multiple IExGs may be the same or different. x in formula (a1-1) １ represents an integer of 2 to 10, and x in formula (a1-2) ２ represents an integer of 2 to 5. １ When the structure (a1-1) and the structure (a1-2) are both included, x １ and 2x ２ The sum of is 2 to 10. １ is preferably 2 to 5, more preferably 2 to 3. ２ is preferably 2 to 3, more preferably 2.

[0051] Structural unit A １ may consist of only the structure (a1-1), or may contain the structure (a1-1) and a structure other than the structure (a1-1). In the latter case, the structure (a1-1) and the structure other than the structure (a1-1) are connected by a linking group (L ３ Similarly, the structural unit A １may consist of only the structure (a1-2), or may contain the structure (a1-2) and a structure other than the structure (a1-2). In the latter case, the structure (a1-2) and the structure other than the structure (a1-2) are connected by a linking group (L ３ ) may be linked.

[0052] Structural unit A １ Specific examples of the structural units include those represented by the following formulae (A1-1) to (A1-4).

[0053]

[0054] IExG and * in formulas (A1-1) to (A1-4), and L in formulas (A1-3) to (A1-4) ３ The plural IExGs may be the same or different, and the plural L ３ may be the same or different from each other.

[0055] Structural unit A in polymer (P) １ From the viewpoints of obtaining better proton conductivity and excellent chemical durability, the structural unit represented by formula (A1-1) to formula (A1-4) is preferable, and the structural unit represented by formula (A1-2) is more preferable.

[0056] [Structural unit A ２ ] Structural unit A ２ is a group in which an arylene group (Ar) having no ion exchange group is bonded to a linking group (L ４ ) and has a continuous structure.

[0057] An arylene group is a divalent aromatic hydrocarbon group and has a structure in which two hydrogen atoms have been removed from an aromatic hydrocarbon. From the viewpoints of solubility in a solvent and film-forming properties, the number of aromatic rings in the arylene group is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1. The arylene group may have a substituent other than an ion-exchange group, but preferably has no substituent.

[0058] Specific examples of the arylene group include a phenylene group, a naphthylene group, a fluorene group, an anthracylene group, a phenanthrylene group, a triphenylene group, a pyrenylene group, and a tetracenylene group.

[0059] Structural unit A ２ From the viewpoints of solubility in a solvent and film-forming properties, the structural unit A preferably contains, as an arylene group, at least one selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group, more preferably contains a phenylene group, and even more preferably contains a 1,4-phenylene group. ２ It is more preferable that the majority of the arylene groups present in the structural unit A are those of the above-mentioned preferred embodiment. ２ It is particularly preferred that all of the arylene groups present therein are each independently a phenylene group, a naphthylene group or a fluorene group.

[0060] Structural unit A ２ From the viewpoint of excellent solubility in a solvent, excellent film-forming property, and excellent mechanical strength during film formation, ４ ) as -SO ２ It is preferred that the group contains at least one group selected from the group consisting of -, -CO-, and a single bond, and -SO ２ From the same viewpoint, it is more preferable that the structural unit A contains - or -CO-. ２ A plurality of linking groups (L ４ It is more preferable that the majority of the structural units A ２ A plurality of linking groups (L ４ ) may all be the preferred embodiments described above.

[0061] Structural unit A ２ The linking group (L ４ ) is preferably a single bond or —SO ２ It is preferable that −.

[0062] Structural unit A ２The number of repetitions (y) of the structure in brackets [ ] in formula (a2) in the above formula is preferably 4 to 12, and more preferably 5 to 10, from the viewpoints of obtaining better proton conductivity and excellent hot water resistance.

[0063] Structural unit A ２ In order to achieve both better proton conductivity and hot water resistance, the number of repetitions (y) of the structure in brackets [ ] in formula (a2) in formula (a1) is preferably 2 to 7 more than the number of repetitions (x) of the structure in brackets [ ] in formula (a1) (x+(2 to 7)).

[0064] Structural unit A ２ From the viewpoints of excellent solubility in a solvent, excellent film-forming ability, and excellent mechanical strength during film formation, it is preferable that the polymerizable compound contains at least one structure selected from the group consisting of a structure represented by the following formula (a2-1) and a structure represented by the following formula (a2-2):

[0065]

[0066]

[0067] Ar and * in formula (a2-1) and formula (a2-2) have the same meanings as defined above. Multiple Ar may be the same or different.

[0068] Structural unit A ２ Specific examples of the structural unit include the structural unit represented by the following formula (A2).

[0069]

[0070] Ar and L in formula (A2) ４ and * are as defined above, Q represents a group having a structure represented by formula (a2-1) or formula (a2-2), and y １ and y ２ each independently represents an integer of 2 to 4. １ and y ２ is preferably 2 to 3. A plurality of Ar may be the same or different, and a plurality of L ４ may be the same or different from each other.

[0071] [Linking Group] From the viewpoint of obtaining better proton conductivity and excellent chemical durability, the polymer (P) contains the structural unit A １ and structural unit A ２ The linking group (L １ or L ２ ) as a single bond, —SO ２ It is preferred that the group contains at least one group selected from the group consisting of —SO ２ From the same viewpoint, it is more preferable that the polymer (P) contains a plurality of structural units A. １ and structural unit A ２ The linking group (L １ and L ２ It is more preferable that the majority of the structural units A) are those of the above-mentioned preferred embodiment, and １ and structural unit A ２ The linking group (L １ and L ２ It is particularly preferred that all of the above are of the preferred embodiments.

[0072] Structural unit A in polymer (P) １ and structural unit A ２ The linking group (L １ and L ２ ) each independently represent a single bond or —SO ２ It is preferable that −.

[0073] As described above, the polymer (P) contains the structural unit A １ and structural unit A ２ The linking group (L １ and L ２ ) plus structural unit A １ Middle and structural unit A ２ Among them, the linking group (L ３ and L ４ ), but from the viewpoint of obtaining better proton conductivity and chemical durability, these linking groups (L １ , L ２ , L ３ and L ４ ) are each independently a single bond or —SO ２It is particularly preferred that -.

[0074] The polymer (P) may be composed of a structure represented by formula (1) and a terminal structure bonded to the structure. The polymer (P) may be, for example, a compound represented by the following formulas (1-1) to (1-3).

[0075]

[0076] A in formulas (1-1) to (1-3) １ , A ２ , L １ , L ２ and n have the same meanings as above. However, in formula (1-1) and formula (1-2), Z ２ L binds to ２ is a single bond. １ and Z ２ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronate ester group. Examples of halogen atoms include a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I). Examples of alkylborane groups include a diethylborane group, a disiamylborane group, a dicyclohexylborane group, and a 9-borabicyclo[3.3.1]nonane group. Examples of boronate ester groups include a pinacol boronate ester group, a 1,3-propanediol boronate ester, a biscyclohexyldiol boronate ester group, a neopentyl glycol boronate ester group, and a catechol boronate ester group.

[0077] The polymer (P) may contain a plurality of polymer units (hereinafter also referred to as "polymer units A") containing the structure represented by formula (1). For example, the polymer (P) may contain three or more polymer units A and a crosslinking group bonding the three or more polymer units A. The polymer (P) having such a crosslinking group (hereinafter also referred to as "crosslinked polymer (P')") has excellent swelling resistance.

[0078] The polymer unit A can be, for example, a compound represented by any one of the above formulas (1-1) to (1-3) having a terminal group Z １ and Z ２Of the two terminal groups of the polymer unit A, the terminal group bonded to the crosslinking group is A １ A may be ２ The terminal group bonded to the crosslinking group may be L ２ (i.e., Z in formula (1-1) and formula (1-2) ２ L binds to ２ When the terminal group attached to the bridging group is A ２ The two end groups of the polymer unit A may be bonded to different crosslinking groups. Of the two end groups of the polymer unit A, the end group opposite to the end group bonded to the crosslinking group is considered to be the end group Z １ and Z ２ The multiple polymer units A bonded to one crosslinking group may be the same or different.

[0079] The crosslinking group may be a group derived from a known crosslinkable compound. From the viewpoint of chemical stability, the crosslinking group preferably has one or more aromatic rings. In this case, it is preferable that the polymer unit A is bonded to the aromatic ring of the crosslinking group. The polymer unit A may be directly bonded to the aromatic ring, and may be bonded to -O-, -S-, or -SO ２ The number of aromatic rings in the bridging group is preferably 1 or 2.

[0080] The crosslinking group may be, for example, a group represented by the following formula (c):

[0081]

[0082] In formula (c), E represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group; ５ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, L ６ represents a single bond, —O—, —S—, or —SO ２represents -, * represents a bond bonding to the polymer unit A, p, q, r and s each represent an integer of 0 to 5, and z represents 0 or 1. However, p+q is 3 or more, p+r is 0 to 5, q+s is 0 to 5, and when z is 0, r and p are 0. When there are multiple E's, the multiple E's may be the same or different from each other. L ５ If there are multiple L ５ may be the same or different. ６ may be the same or different from each other.

[0083] The group represented by formula (c) may be, for example, a group represented by the following formulae (c1) to (c5). The symbols in formulae (c1) to (c5) have the same meanings as above. Some or all of E in the groups represented by formulae (c1) to (c5) may be replaced with hydrogen atoms.

[0084]

[0085] The number of crosslinking groups contained in the crosslinked polymer (P') may be one or more. The multiple crosslinking groups may be the same or different from one another.

[0086] The crosslinked polymer (P') may contain a crosslinking group bonding two polymer units A. Such a crosslinking group may have the same structure as the crosslinking group bonding three or more polymer units A, except that the number of bonds bonding to the polymer unit A is different.

[0087] The proportion of the structure represented by formula (1) in the entire polymer (P) is preferably 80% by mass or more, from the viewpoint of obtaining better proton conductivity. From the same 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 but less than 100% by mass, or 85% by mass or more but less than 100% by mass.

[0088] The polymer (P) may contain fluorine atoms, but the fluorine content in the polymer (P) is preferably 5 mass% or less, and it is preferable that the polymer (P) does not contain fluorine atoms (the fluorine content is below the detection limit).

[0089] 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 excellent proton conductivity and excellent mechanical strength during membrane formation, and may be 300,000 or less, 200,000 or less, or 150,000 or less from the viewpoint of excellent solubility in solvents and membrane formability. 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.

[0090] The weight average molecular weight of the polymer (P) may be 40,000 or more, 50,000 or more, or 60,000 or more from the viewpoint of superior proton conductivity and superior mechanical strength during membrane formation, and may be 500,000 or less, 300,000 or less, or 200,000 or less from the viewpoint of superior solubility in solvents and membrane formability. From these viewpoints, the weight average molecular weight of the polymer (P) may be 40,000 to 500,000, 50,000 to 300,000, or 60,000 to 200,000.

[0091] The ratio of the weight average molecular weight to the number average molecular weight (polydispersity) of the polymer (P) may be 2.0 or more, 2.5 or more, or 2.8 or more. When the polydispersity of the polymer (P) is 2.5 or more, excellent swelling resistance tends to be obtained. From the viewpoint of solubility in a solvent, the polydispersity of the polymer (P) may be 20.0 or less, 15.0 or less, or 10.0 or less. The polydispersity of the polymer (P) may be 2.0 to 20.0, 2.5 to 20.0, 2.5 to 15.0, or 2.8 to 10.0.

[0092] The number average molecular weight and weight average molecular weight of the polymer (P) are values ​​measured by gel permeation chromatography (GPC) and calculated as standard polyethylene glycol / oxide (PEG / PEO).

[0093] The 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, the polymer (P) can be a polymer of the compound (b1) and the compound (b2).

[0094]

[0095] In formula (b1), A １ has the same meaning as above, and X １ｂ and X ２ｂ are each independently a halogen atom. Examples of halogen atoms include a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I).

[0096]

[0097] In formula (b2), A ２ has the same meaning as above, and Z １ｂ and Z ２ｂ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of the halogen atom, the alkylborane group, and the boronic acid ester group are the same as those described above in Z １ and Z ２ These are the same as the examples of the halogen atom, alkylborane group and boronic acid ester group represented by the following formula:

[0098] In the above method, the structural unit A １ and structural unit A ２ Therefore, according to the above method, the number of repetitions n in formula (1) can be easily increased to 10 or more.

[0099] According to the above method, L in formula (1) １ and L ２ is —O—, —S— or a single bond. １ｂ and Z ２ｂ When at least one of the groups is a hydroxy group, L １ and L２ A polymer (P) is obtained in which at least one of the following is —O—, and Z １ｂ and Z ２ｂ When at least one of the groups is a thiol group, L １ and L ２ A polymer (P) is obtained in which at least one of Z １ｂ and Z ２ｂ When at least one of the groups is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, L in formula (1) １ and L ２ A polymer (P) is obtained in which at least one of the following is a single bond.

[0100] Compound (b1) includes X １ｂ and / or X ２ｂ Similarly, as the compound (b2), a plurality of compounds having different Z １ｂ and / or Z ２ｂ It is possible to use a plurality of compounds with different

[0101] The compound (b1) and the compound (b2) can be reacted (polymerized) by, for example, an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0102] The solvent used in the reaction is preferably a good solvent for compound (b1), compound (b2), and polymer (P) and capable of increasing the molecular weight of polymer (P) during polymerization. For example, N-methyl-pyrrolidone, 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 alone or as a mixture of two or more.

[0103] The base is used to improve the nucleophilicity of compound (b2). The base is not particularly limited as long as it can deprotonate compound (b2). For example, hydroxides and carbonates of alkali metals (lithium, sodium, potassium, rubidium, cesium), hydroxides and carbonates of alkaline earth metals (magnesium, calcium, strontium, barium), and organic bases such as amines can be used.

[0104] The reaction temperature may be in the range of 25° C. to 350° C. From the viewpoint of excellent reaction rate, the reaction temperature is preferably 60° C. or higher, more preferably 100° C. or higher. From the viewpoint of suppressing decomposition of the polymer, the reaction temperature is preferably 300° C. or lower, more preferably 250° C. or lower.

[0105] Compound (b1) and compound (b2) can also be reacted (polymerized) by, for example, 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 the examples of solvents that can be used in the above-mentioned aromatic nucleophilic substitution reaction.

[0106] The catalyst is not particularly limited as long as it can promote a cross-coupling reaction, and conventionally known catalysts can be used. For a coupling reaction between halogens, for example, a copper catalyst, a nickel catalyst, or a palladium catalyst can be used. For a coupling reaction between a halogen and a boronic acid group, an alkylborane group, or a boronic acid ester group, for example, a conventionally known catalyst (e.g., a palladium catalyst, a nickel catalyst) used in the Suzuki-Miyaura coupling reaction can be used.

[0107] Examples of copper catalysts include copper(I) 2-thiophenecarboxylate and copper(I) tetrakis(acetonitrile)hexafluorophosphate.

[0108] Examples of nickel catalysts include bis(1,5-cyclooctadiene)nickel(0), dibromobis(triphenylphosphine)nickel(II), and [1,1′-bis(diphenylphosphino)ferrocene]dichloronickel(II).

[0109] Examples of the palladium catalyst include tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(triphenylphosphine)palladium(II) dichloride, and [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II).

[0110] The reaction temperature may be in the range of 0° C. to 350° C. From the viewpoint of excellent reaction rate, the reaction temperature is preferably 30° C. or higher, more preferably 60° C. or higher. From the viewpoint of suppressing decomposition of the polymer, the reaction temperature is preferably 300° C. or lower, more preferably 250° C. or lower.

[0111] In the aromatic nucleophilic substitution reaction and cross-coupling reaction, it is preferable to remove water from the reaction system in order to increase the molecular weight of the polymer (P). The dehydration method is not particularly limited, but examples include a method of azeotropic dehydration in which an azeotropic solvent is present in the reaction system, a method of heating above the boiling point of water to continuously remove it from the reaction system, and a method of using a water-absorbing agent such as a molecular sieve. The azeotropic solvent is not particularly limited as long as it can remove water, and examples include benzene, toluene, cyclohexane, and xylene.

[0112] The aromatic nucleophilic substitution reaction and cross-coupling reaction are preferably carried out under an inert atmosphere (e.g., under a nitrogen atmosphere or an argon atmosphere). After the polymerization reaction is completed, 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 to precipitate and recover the polymer as a solid, and removing the solvent from the reaction solution by evaporation to recover the polymer as a solid. Methods for purifying the polymer include, for example, washing the polymer in a solvent in which the polymer has low solubility but in which by-produced inorganic salts and compounds derived from residual monomers have high solubility, and washing using a Soxhlet extractor. The methods for recovering and purifying the polymer are not limited to these methods.

[0113] The polymer (P) can also be obtained by oxidizing a polymer having a structure represented by formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, the polymer (P) can be obtained by oxidizing a polymer having a structure represented by formula (1) in which L １ , L ２ , L ３ or L ４ The sulfide-containing polymer may be an oxide of a polymer containing —S— (sulfide group) as the group (hereinafter referred to as a “sulfide-containing polymer”). From the viewpoint of excellent chemical durability, the sulfide-containing polymer is a polymer having a structure represented by formula (1), １ , L ２ , L ３ and L ４ each independently represents a single bond, —S—, or —SO ２ Preferably, the polymer is -.

[0114] The method for oxidizing the sulfide-containing polymer is not particularly limited, and may be, for example, by oxidizing a sulfide group (—S—) to form a sulfonyl group (—SO ２ The sulfide-containing polymer may be immersed in a mixed solution containing acetic acid, sulfuric acid, and hydrogen peroxide. The concentration of acetic acid in the mixed solution may be, for example, 50 to 90 mass %. The concentration of sulfuric acid in the mixed solution may be, for example, 5 to 25 mass %. The concentration of hydrogen peroxide in the mixed solution may be, for example, 1 to 15 mass %. The immersion time may be, for example, 1 to 100 hours. In the above method, heating may be performed after immersion. The heating temperature may be, for example, 30 to 120°C, and the heating time may be, for example, 0.1 to 24 hours.

[0115] The polymer (P) obtained by the above method is a polymer having a structure represented by formula (1), wherein L １ , L ２ , L ３ or L ４ As -SO ２The polymer may be a polymer in which all of the sulfide groups in the sulfide-containing polymer have been oxidized to sulfonyl groups (complete oxide), or a polymer in which only a portion of the sulfide groups in the sulfide-containing polymer have been oxidized to sulfonyl groups (partial oxide). The degree of oxidation can be adjusted, for example, by the impregnation time, heating temperature, and heating time.

[0116] The polymer (P) can also be obtained by reacting (polymerizing) a polymer of compound (b1) and compound (b2) or an oxide thereof with a compound having three or more groups that react with the polymer or the oxide thereof to form crosslinks (hereinafter also referred to as "crosslinkable compound (d)"). That is, the polymer (P) can be a reaction product of a polymer of compound (b1) and compound (b2) or an oxide thereof with the crosslinkable compound (d).

[0117] The above method can produce a crosslinked product (for example, the above-mentioned crosslinked polymer (P')) containing a polymer of compound (b1) and compound (b2) or an oxide thereof as a polymer unit. The above method can form a crosslinked structure while maintaining a precise array structure, thereby achieving both excellent proton conductivity and excellent swelling resistance.

[0118] The crosslinkable compound (d) may be a known crosslinkable compound, for example, a low molecular weight compound having a molecular weight of not more than 1000. The group that reacts with the polymer or its oxide to form a crosslink is, for example, a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

[0119] From the viewpoint of chemical stability, the crosslinkable compound (d) preferably has one or more aromatic rings. In this case, the group that reacts with the polymer or its oxide to form a crosslink is preferably directly bonded to the aromatic ring. The number of aromatic rings in the crosslinkable compound (d) is preferably 1 or 2.

[0120] The crosslinkable compound (d) may be, for example, a compound represented by the following formula (d):

[0121]

[0122] In formula (d), E, ​​L ５ and z are as defined above, and t and u each represent an integer of 0 to 5, provided that t+u is 3 or more, and when z is 0, t is 0. The multiple E's may be the same or different. Of the multiple E's, three or more E's are terminal groups (X １ｂ , X ２ｂ , Z １ｂ or Z ２ｂ ) to form crosslinks.

[0123] The polymer of the compound (b1) and the compound (b2) and the oxide thereof, and the crosslinkable compound (d) may each be used alone or in combination of two or more kinds.

[0124] The reaction of the polymer of the compound (b1) and the compound (b2) or the oxide thereof with the crosslinkable compound (d) can be carried out in the same manner as the reaction of the compound (b1) with the compound (b2).

[0125] <Electrolyte Material and Electrolyte Membrane> The electrolyte material of one embodiment is a material containing an electrolyte, and contains the polymer (P) as the electrolyte. The electrolyte membrane of one embodiment is a membrane containing an electrolyte, and contains the polymer (P) as the electrolyte. The electrolyte material is used to form the electrolyte membrane. That is, the electrolyte membrane may be made of the electrolyte material.

[0126] The electrolyte material and the electrolyte membrane contain the polymer (P) and therefore have excellent proton conductivity.

[0127] The electrolyte material and the electrolyte membrane may also have a microphase-separated structure when immersed in water (wet state). Specifically, when the electrolyte membrane is subjected to small-angle X-ray scattering (SAXS) measurement while immersed in water, the peak interplanar spacing obtained may be 4.0 nm or more.

[0128] The electrolyte material and the electrolyte membrane may also have a microphase-separated structure in a vacuum-dried state (dry state). Specifically, when the electrolyte membrane is subjected to small-angle X-ray scattering (SAXS) measurement in a vacuum-dried state, the peak spacing obtained may be 2.5 nm or more.

[0129] The electrolyte material and the electrolyte membrane may consist of only the polymer (P), or may contain the polymer (P) and components other than the polymer (P) (such as additives). That is, the electrolyte material may be a composition. The content of the polymer (P) in the electrolyte material and the electrolyte membrane may be 90 to 100 mass%, 94 to 100 mass%, or 97 to 100 mass%. The above content is based on the total solid content of the electrolyte material or the electrolyte membrane.

[0130] Components other than the polymer (P) that can be contained in the electrolyte material and the electrolyte membrane include water-retentive inorganic substances and radical scavengers, specifically, for example, water, silica, cerium oxide, and manganese oxide. These may be used alone or in combination.

[0131] The thickness of the electrolyte membrane is not particularly limited and can be changed depending on the size of the fuel cell, etc. From the viewpoint of increasing the mechanical strength of the membrane and reducing the membrane resistance, the thickness of the electrolyte membrane may be, for example, 1 to 200 μm, 1 to 100 μm, or 1 to 50 μm.

[0132] The method for producing the electrolyte membrane is not particularly limited, and the electrolyte membrane can be produced by a known method for producing a membrane of an electrolyte polymer, such as a solution casting method, a dispersion casting method, a melt pressing method, or a melt extrusion method.

[0133] In the solution casting method, for example, a solution containing a polymer (P) is used as an electrolyte material, the solution is cast onto a substrate, the solvent is removed, and then the membrane is peeled off from the substrate, thereby obtaining an electrolyte membrane.

[0134] The solvent used in the solution casting method is not particularly limited as long as it is a solvent that can dissolve the polymer (P), and examples thereof include N-methyl-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea. These may be used alone or in combination.

[0135] In the dispersion casting method, for example, a dispersion containing a polymer (P) is used as an electrolyte material, and the dispersion is cast onto a substrate, the dispersion medium is removed, and then the membrane is peeled off from the substrate, thereby obtaining an electrolyte membrane.

[0136] The dispersion medium used in the dispersion casting method is not particularly limited as long as it is a dispersion medium capable of dispersing the polymer (P), and examples thereof include water, ethers, alcohols, ketones, 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. These may be used alone or in combination.

[0137] The electrolyte material and the electrolyte membrane are suitable for use in polymer electrolyte fuel cells and polymer electrolyte water electrolysis devices. The electrolyte material and the electrolyte membrane can also be used in redox flow batteries, electrochemical hydrogen pumps, chloralkali electrolysis devices, solid acid catalysts, membrane-type humidity control devices, gas separation membranes, etc.

[0138] The electrolyte membrane can also be used by being attached to a microporous membrane, a nonwoven fabric, a mesh, etc. That is, another embodiment of the present disclosure is a laminate including an electrolyte membrane and another membrane (a microporous membrane, a nonwoven fabric, a mesh, etc.).

[0139] <Catalyst-Coated Electrolyte Membrane> An electrolyte membrane with a catalyst layer of one embodiment includes the electrolyte membrane of the above-described embodiment and a catalyst layer disposed on one or both surfaces of the electrolyte membrane.

[0140] The catalyst layer is, for example, a layer composed of an anode catalyst or a cathode catalyst in a polymer electrolyte fuel cell, a polymer electrolyte water electrolysis device, etc. Hereinafter, a layer composed of an anode catalyst will be referred to as an anode catalyst layer, and a layer composed of a cathode catalyst will be referred to as a cathode catalyst layer.

[0141] The configuration of the catalyst layer is not particularly limited and may be a conventionally known configuration as a catalyst layer (anode catalyst layer, cathode catalyst layer) for a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device. The catalyst layer may be formed, for example, from a conductive composition containing an anode catalyst or a cathode catalyst and a conductive material. The catalyst layer may also contain an ionomer.

[0142] As the anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of a fuel such as hydrogen can be used, and as the anode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the oxygen generation reaction can be used, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys of two or more of these. These may be used alone or in combination of two or more.

[0143] The cathode catalyst in a polymer electrolyte fuel cell can be a metal catalyst capable of promoting an oxygen reduction reaction, and the cathode catalyst in a polymer electrolyte water electrolysis device can be a metal catalyst capable of promoting a hydrogen generation reaction, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, or an alloy of two or more of these metals. These metals may be used alone or in combination.

[0144] 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 alone or in combination of two or more.

[0145] As the ionomer, a conventionally known material can be used, for example, an ionomer containing a perfluoro-based electrolyte can be used. The above-mentioned polymer (P) can also be used as the ionomer. It is preferable to use a material with high oxygen permeability as the ionomer. There is no particular limitation on the amount of ionomer added to the catalyst layer, but it is preferable to adjust the amount added within a range in which oxygen diffusion is not easily inhibited.

[0146] The catalyst layer may further contain additives such as a water repellent such as fluorinated carbon, and a binder such as a fluorine-containing resin or a hydrocarbon resin having a sulfonic group.

[0147] A laminate having an anode catalyst layer and a cathode catalyst layer on both sides of an electrolyte membrane (for example, a laminate having a layer structure of "anode catalyst layer / electrolyte membrane / cathode catalyst layer") is also called a CCM (Catalyst Coated Membrane), and is suitably used in solid polymer fuel cells and solid polymer water electrolysis devices.

[0148] In the above embodiment, a laminate including the above-mentioned other membranes (microporous membrane, nonwoven fabric, mesh, etc.) can also be used instead of the electrolyte membrane.

[0149] <Membrane Electrode Assembly> A membrane electrode assembly of one embodiment includes the electrolyte membrane of the above embodiment and electrode layers disposed on one or both surfaces of the electrolyte membrane.

[0150] The electrode layer includes, for example, the catalyst layer (anode catalyst layer or cathode catalyst layer) in the catalyst-coated electrolyte membrane of the above embodiment. Hereinafter, an electrode layer including an anode catalyst layer will be referred to as an anode layer, and an electrode layer including a cathode catalyst layer will be referred to as a cathode layer.

[0151] The configuration of the electrode layer is not particularly limited and may be a conventionally known configuration as the electrode layer (anode layer, cathode layer) of a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device. The electrode layer may be composed of, for example, the above-mentioned catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion substrate. When the catalyst layer itself has gas diffusibility, the electrode layer may be composed of only the catalyst layer. As the gas diffusion substrate, for example, a porous membrane can be used. As the gas diffusion substrate, a material having water repellency and conductivity in addition to gas diffusibility (for example, a carbon fiber substrate such as a carbon nonwoven fabric or carbon paper, or a titanium fiber sintered compact) can also be used.

[0152] A laminate comprising an anode layer and a cathode layer as electrode layers on both sides of an electrolyte membrane (for example, a laminate having a layer structure 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 solid polymer fuel cells and solid polymer water electrolysis devices.

[0153] In the above embodiment, a laminate including the above-mentioned other membranes (microporous membrane, nonwoven fabric, mesh, etc.) can also be used instead of the electrolyte membrane.

[0154] <Solid Polymer Electrolyte Fuel Cell> A solid polymer fuel cell of one embodiment includes the membrane electrode assembly of the above embodiment.

[0155] The configuration of the polymer electrolyte fuel cell is not particularly limited and may be a conventionally known configuration, except for the use of the membrane electrode assembly of the above embodiment. The polymer electrolyte fuel cell may include, for example, two or more membrane electrode assemblies. The two or more membrane electrode assemblies may be stacked (laminated) with a separator interposed therebetween. As the separator, a conventionally known separator for polymer electrolyte fuel cells can be used.

[0156] <Solid polymer water electrolysis device> A solid polymer water electrolysis device of one embodiment includes the membrane electrode assembly of the above embodiment.

[0157] The configuration of the solid polymer water electrolysis device is not particularly limited and may be a conventionally known configuration except for the use of the membrane electrode assembly of the above embodiment. The solid polymer water electrolysis device may further include, for example, a power feeder on the outside of the membrane electrode assembly. Furthermore, the solid polymer water electrolysis device may include two or more membrane electrode assemblies.

[0158] The present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to the following examples.

[0159] Synthesis Example 1 (Synthesis of Hydrophilic Monomer (M1)) A 10 L flask equipped with a dropping funnel, a reflux condenser, and a mechanical stirrer was purged with nitrogen, and 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of dehydrated tetrahydrofuran were charged, and stirring was initiated. The flask was cooled to -70°C in a methanol-dry ice bath, and 320 mL of a 2.6 mol / L n-butyllithium-hexane solution was added dropwise. The mixture was stirred for 1 hour while cooled in the bath. 40 mL of sulfur dioxide gas was introduced into the flask using nitrogen gas. The mixture was stirred for 30 minutes while cooled in the bath. The bath was then removed, and the internal 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, and 260 mL of 35% hydrogen peroxide solution was added and stirred for 18 hours. The solid was removed by suction filtration, and 600 g of sodium chloride was added to the collected filtrate. The precipitated white solid was collected by suction filtration and purified by recrystallization from water / isopropyl alcohol. The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer represented by the following formula (M1). The yield was 65%.

[0160]

[0161] Synthesis Example 2 (Synthesis of Hydrophobic Monomer (M2)) A 200 mL flask equipped with a stirrer, a Dean-Stark tube, a reflux condenser, and a calcium chloride tube was charged with 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, and 50 mL of N,N-dimethylacetamide (DMAc) and 50 mL of toluene were added. The temperature was raised to 160°C in an oil bath with stirring, and heating and stirring were continued for 4 hours. The toluene was removed from the Dean-Stark tube, and the temperature was raised to 180°C in an oil bath. After heating, heating and stirring were continued for 8 hours. After allowing the reaction solution to cool to room temperature, the reaction solution 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 NMP / ethanol. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0162]

[0163] Synthesis Example 3 (Synthesis of Hydrophobic Monomer (M3)) A 500 mL flask equipped with a stirrer and a condenser was purged with nitrogen. 41 g of 4,4'-thiobisbenzenethiol, 14 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 80 mL of DMAc, and 4 g of potassium carbonate were added to the flask. The temperature was raised to 100°C in an oil bath with stirring, and heating and stirring was continued for 6 hours. After allowing the reaction solution to cool, 100 mL of 1 M hydrochloric acid was added, and the precipitated solid was collected by suction filtration. The collected solid was dissolved in dichloromethane and purified by silica column chromatography using dichloromethane as a developing solvent. Fractions containing the target product were collected, and the solvent was distilled off using an evaporator. The obtained solid was purified by recrystallization from dichloromethane. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M3) represented by the following formula (M3). The yield was 40%.

[0164]

[0165] Synthesis Example 4 (Synthesis of Hydrophobic Monomer (M4)) A 500 mL flask equipped with a stirrer and a condenser was purged with nitrogen. To this flask were added 20 g of anhydrous aluminum chloride, 10 g of isophthaloyl chloride, and 240 mL of 1,2-dichlorobenzene. While stirring the reaction solution, 24 g of 3-bromo-1,1'-biphenyl was added dropwise. The reaction solution was heated to 40°C, and heating and stirring were continued for 3 hours. After allowing the reaction solution to cool to room temperature, the reaction solution was added to 900 mL of ice-cooled 3% hydrochloric acid, and stirring was continued at room temperature for 18 hours. The precipitated white solid was collected by suction filtration and washed with ethanol. The obtained solid was dried under reduced pressure and used in the subsequent reaction.

[0166] 0.80 g of the resulting dried solid, 0.71 g of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol, 0.11 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride dichloromethane adduct, and 0.57 g of sodium carbonate were added to a 100 mL flask and purged with nitrogen. 30 mL of tetrahydrofuran (THF) was added, and the reaction solution was heated to 50°C with vigorous stirring. Heating and stirring were continued at 50°C for 22 hours. After allowing the reaction solution to cool, 100 mL of chloroform and 100 mL of 5% hydrochloric acid were added, followed by phase separation, and the organic layer was recovered. The solvent was removed using an evaporator, and 20 mL of ethyl acetate was added to form a suspension. The suspension was subjected to suction filtration, the filtrate was recovered, and the solvent was removed using an evaporator to obtain an orange oily substance. The resulting oily substance was dissolved in ethyl acetate and purified by silica column chromatography using a 1:1 (volume ratio) mixed solvent of ethyl acetate and hexane as the developing solvent. The fraction containing the target substance was collected, and the solvent was removed using an evaporator. The resulting solid was purified by recrystallization from hot toluene. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M4) represented by the following formula (M4). The yield was 60%.

[0167]

[0168] Synthesis Example 5 Synthesis of Hydrophobic Monomer (M5) A hydrophobic monomer (M5) represented by the following formula (M5) was obtained in the same manner as in Synthesis Example 4, except that 0.96 g of 4'-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)biphenyl-4-ol was used instead of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol. The yield was 47%.

[0169]

[0170] Synthesis Example 6 (Synthesis of Hydrophobic Monomer (M6)) A 500 mL flask equipped with a stirrer and a condenser was purged with nitrogen. To this flask were added 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)phenol, 19 g of potassium carbonate, 2.0 g of tetrakis(triphenylphosphine)palladium(0), and 250 mL of tetrahydrofuran. The reaction solution was heated to 90°C and continued to be heated and stirred for 3 hours. After the reaction solution was allowed to cool to room temperature, 200 mL of water and 500 mL of ethyl acetate were added, followed by separation, and the organic layer was recovered. The solvent was removed using an evaporator, and the resulting crude product was purified by silica column chromatography using a mixed solvent of ethyl acetate / hexane = 1 / 1 (volume ratio) as a developing solvent. The fraction containing the target product was recovered, and the solvent was removed using an evaporator. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M6) represented by the following formula (M6). The yield was 53%.

[0171]

[0172] Comparative Example 1 (Synthesis of Polymer (P1)) 1.334 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 0.816 g of disodium diphenylsulfone-4,4'-dichloro-3,3'-disulfonate, and 0.551 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Subsequently, 10 mL of DMAc and 10 mL of toluene were added. The mixture was heated to 160°C and refluxed for 4 hours, after which the toluene was removed from the Dean-Stark tube. The mixture was heated to 180°C and polymerization was performed for 21 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 300 mL of isopropyl alcohol (IPA), and a solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P1) having a structure represented by the following formula (P1). The yield was 90%. Note that n in formula (P1) was calculated from the number average molecular weight described below. The same applies to n in formulas (P2) to (P8) described below.

[0173] [In formula (P1), M represents Na, K, or H, and n represents a positive number (approximately 31).]

[0174] (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 calculated. Mn was 39,000, Mw was 130,000, and Mw / Mn was 3.3.

[0175] [Measurement Conditions] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by GPC. The polymer (P1) was dissolved at a concentration of 1 mg / mL in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L of lithium bromide) to prepare a sample solution. The HLC-8320 GPC manufactured by Tosoh Corporation was used. Two Tosoh TSKgel SuperAWM-H columns (inner diameter 6.0 mm, length 15 cm) were used. A differential refractometer detector was used. Measurements were performed at a flow rate of 0.6 mL / min and a temperature of 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were calculated in terms of standard polyethylene glycol / oxide (PEG / PEO). The polydispersity index (Mw / Mn) was calculated by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0176] (Preparation of Electrolyte Membrane) The obtained polymer (P1) was dissolved in DMAc to obtain a solution containing 10% by mass of polymer (P1). The obtained solution was cast onto a glass substrate and dried at 60°C for 12 hours to obtain a membrane (thickness: 24 µm). The membrane thickness was measured at 25 points in the surface using a PG-02 constant pressure thickness gauge manufactured by TECLOCK CORPORATION, and the average value was used. The obtained membrane was immersed in 1 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ ), then the membrane was immersed in pure water to thoroughly wash, and dried under reduced pressure to obtain a polymer electrolyte membrane of Comparative Example 1 (an electrolyte membrane made of proton-substituted polymer (P1), having a membrane thickness of 24 μm).

[0177] (Evaluation) [Proton Conductivity Evaluation] The proton conductivity of the obtained polymer electrolyte membrane was measured by the following method. Using a Teflon (registered trademark) measurement cell (BT-115, manufactured by Scribner), the prepared electrolyte membrane was placed in contact with four platinum wires. After maintaining the membrane at 70% relative humidity for 2 hours, the humidity was increased from 20% relative humidity and, while maintaining the set humidity, DC resistance measurement was performed using a four-terminal method. The proton conductivity in the in-plane direction of the electrolyte membrane was calculated from the obtained resistance value, the thickness of the polymer electrolyte membrane, and the distance between the terminals. The proton conductivity of the polymer electrolyte membrane of this comparative example was 60 mS / cm (80°C, 100% relative humidity).

[0178] [Gas Permeability Test] The gas permeability of the obtained polymer electrolyte membrane was evaluated in accordance with the gas permeability test method (JIS K 7126-2) using the isobaric method. Specifically, the polymer electrolyte membrane was first mounted between two chambers of a permeation cell in a sealed state. Hydrogen, which was the measurement gas, was supplied to one side of the polymer electrolyte membrane, and Ar gas, which was the carrier gas, was supplied to the other side. The relative humidity was adjusted by the humidifier temperature of each supplied gas and the cell temperature. The measurement gas that had permeated the polymer electrolyte membrane was supplied to a gas chromatograph together with the carrier gas, and the gas permeability was measured from the detection data and flow rate. The gas permeability (cm ) was calculated from the obtained gas permeability and the thickness of the polymer electrolyte membrane. ３ mm / (cm ２ The hydrogen gas permeability of the polymer electrolyte membrane of this comparative example was calculated to be 0.71×10 －７ cm ３ mm / (cm ２ ·s·kPa) (80°C, relative humidity 60%).

[0179] [Small-Angle X-Ray Scattering (SAXS) Measurement] Small-angle X-ray scattering (SAXS) measurement of the polymer electrolyte membrane was carried out in a dry state (under vacuum) and a wet state (immersed in water) under the following conditions: Apparatus name: NanoSTAR manufactured by Bruker Japan; Voltage and current: 45 kV and 120 mA; X-ray wavelength: Cu Kα ray; Camera length: 104.3 cm; Exposure time: 60 minutes (dry state), 180 minutes (wet state).

[0180] For the obtained small-angle scattering profile, the peak top position q ｍａｘ Therefore, the interplanar spacing d (= 2π / q ｍａｘ For the polymer electrolyte (P1), no small-angle scattering peak was observed in the dry state, but d = 4.0 nm in the wet state.

[0181] [Volume Swelling Ratio Measurement] A 3 cm square membrane was punched out from the obtained polymer electrolyte membrane, and the punched membrane was immersed in 50 mL of pure water at 80°C for 1 hour. The dimensional change before and after immersion in pure water was measured to calculate the membrane volume. The volume swelling ratio was calculated by dividing the volume of the membrane after immersion in pure water by the volume of the membrane before immersion in pure water. The volume swelling ratio was 55%.

[0182] Comparative Example 2 In Comparative Example 2, a commercially available Nafion® was used as an evaluation sample. ＴＭ NR211 (film thickness 25 μm) was used and various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were carried out in the same manner as in Comparative Example 1. The proton conductivity was 130 mS / cm (80°C, relative humidity 100%), and the hydrogen gas permeability was 1.03 × 10 －７ cm ３ mm / (cm ２ The surface tension was 1.5 s kPa (80°C, relative humidity 60%). The interplanar spacing d in the dry state and the wet state measured by SAXS was 3.3 nm and 5.3 nm, respectively. The volume swelling ratio was 61%. In the following examples, the Nafion ＴＭ Based on the volume swelling ratio of NR211, an electrolyte membrane was evaluated to have excellent swelling resistance when its volume swelling ratio was 61% or less.

[0183] Example 1 Synthesis of Polymer (P2) 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 to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Subsequently, 10 mL of dimethyl sulfoxide (DMSO) and 10 mL of cyclohexane were added. The mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 150 hours while still heated at 130°C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 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 a polymer (P2) having a structure represented by the following formula (P2). The yield was 97%. The Mn of polymer (P2) measured in the same manner as in Comparative Example 1 was 30,000, the Mw was 61,000, and the Mw / Mn was 2.0.

[0184] [In formula (P2), M represents Na, K, or H, and n represents a positive number (approximately 20).]

[0185] (Preparation of Electrolyte Membrane) The obtained polymer (P2) was dissolved in DMSO to obtain a solution containing 10% by mass of polymer (P2). The obtained solution was cast onto a glass substrate and dried at 60°C for 12 hours to obtain a membrane (thickness: 49 µm). The obtained membrane was immersed in 1 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ ), then the membrane was immersed in pure water to thoroughly wash, and dried under reduced pressure to obtain a polymer electrolyte membrane of Example 1 (electrolyte membrane made of proton-substituted polymer (P2), membrane thickness 49 μm).

[0186] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 231 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.15×10－７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. In the SAXS measurement, as shown in FIG. 1, clear peaks were confirmed in both the dry and wet states. The lattice spacing d in the dry and wet states by SAXS measurement was 3.6 nm and 5.5 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in both the dry and wet states. The volume swelling ratio was 184%.

[0187] Example 2 Synthesis of Polymer (P3) 2.711 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, 2.664 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.352 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Then, 25 mL of DMSO and 25 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. The reaction solution was heated to 140°C and polymerization was performed for 260 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 500 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 a polymer (P3) having a structure represented by the following formula (P3). The yield was 88%. The Mn of polymer (P3) measured in the same manner as in Comparative Example 1 was 33,000, the Mw was 75,000, and the Mw / Mn was 2.3.

[0188] [In formula (P3), M represents Na, K, or H, and n represents a positive number (approximately 20).]

[0189] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 2 (an electrolyte membrane made of proton-substituted polymer (P3)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P3). The thickness of the polymer electrolyte membrane was 37 μm.

[0190] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 185 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.14 × 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry and wet states measured by SAXS was 3.9 nm and 5.4 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in the dry and wet states. The volume swelling ratio was 94%.

[0191] Example 3 (Synthesis of Polymer (P4) and Preparation of Electrolyte Membrane) The polymer (P3) obtained in Example 2 was dissolved in DMSO to obtain a solution containing 10% by mass of polymer (P3). The obtained solution was cast onto a glass substrate and dried at 60°C for 12 hours to obtain a membrane (thickness 37 μm). The obtained membrane was immersed in a mixed solution consisting of 80 mL of acetic acid, 8 mL of sulfuric acid, and 7 mL of hydrogen peroxide, and stirred at 30°C for 48 hours. Thereafter, the mixture was heated and stirred at 105°C for 10 minutes. The obtained membrane was immersed in pure water and thoroughly washed, and dried under reduced pressure to obtain a membrane (thickness 37 μm) made of polymer (P4) having a structure represented by the following formula (P4). The Mn of polymer (P4) measured in the same manner as above was 37,000, the Mw was 84,000, and the Mw / Mn was 2.3. The infrared absorption spectra of the polymer membrane before and after the oxidation reaction were measured, and a peak at 1570 cm －１ and 1470 cm －１ The absorption peak at 1330 cm disappeared after oxidation. －１ The absorption peak intensity at 1570 cm －１ and 1470 cm －１ The absorption peak is due to the ring stretching vibration of the benzene ring with the -S- bond, and is at 1330 cm －１ The absorption peak of -SO２ -bond stretching vibration, the -S- bond becomes -SO ２ - It was confirmed that the bond was oxidized.

[0192] [In formula (P4), M represents Na, K, or H, and n represents a positive number (approximately 20).]

[0193] The obtained membrane was immersed in 1 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ ), then the membrane was immersed in pure water to thoroughly wash, and dried under reduced pressure to obtain a polymer electrolyte membrane of Example 3 (an electrolyte membrane made of proton-substituted polymer (P4), a membrane thickness of 37 μm).

[0194] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 172 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.11 x 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry and wet states measured by SAXS was 3.9 nm and 5.2 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in both the dry and wet states. The volume swelling ratio was 74%.

[0195] Example 4 Synthesis of Polymer (P5) 0.816 g of the hydrophobic monomer (M4) obtained in Synthesis Example 4, 1.195 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.652 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. 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. The reaction solution was heated to 140°C and polymerization was performed for 100 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 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 a polymer (P5) having a structure represented by the following formula (P5). The yield was 85%. The Mn of polymer (P5) measured in the same manner as in Comparative Example 1 was 28,000, the Mw was 66,000, and the Mw / Mn was 2.4.

[0196] [In formula (P5), M represents Na, K, or H, and n represents a positive number (approximately 20).]

[0197] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 4 (an electrolyte membrane made of proton-substituted polymer (P5)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P5). The thickness of the polymer electrolyte membrane was 31 μm.

[0198] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 232 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.13 × 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭIt was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry and wet states measured by SAXS was 3.4 nm and 5.2 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in both the dry and wet states. The volume swelling ratio was 506%.

[0199] Example 5 Synthesis of Polymer (P6) 0.924 g of the hydrophobic monomer (M5) obtained in Synthesis Example 5, 1.087 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.593 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. The mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. The mixture was heated to 150°C and polymerization was performed for 120 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 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 a polymer (P6) having a structure represented by the following formula (P6). The yield was 94%. The Mn of the polymer (P6) measured in the same manner as in Comparative Example 1 was 29,000, the Mw was 59,000, and the Mw / Mn was 2.0.

[0200] [In formula (P6), M represents Na, K, or H, and n represents a positive number (approximately 20).]

[0201] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 5 (an electrolyte membrane made of proton-substituted polymer (P6)) was obtained in the same manner as in Example 1, except that polymer (P6) was used instead of polymer (P2). The thickness of the electrolyte membrane was 52 μm.

[0202] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 188 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.11 x 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry and wet states measured by SAXS was 3.8 nm and 5.6 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in both the dry and wet states. The volume swelling ratio was 114%.

[0203] Example 6 Synthesis of Polymer (P7) 0.932 g of the hydrophobic monomer (M6) obtained in Synthesis Example 6, 1.297 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.593 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Subsequently, 10 mL of DMSO and 10 mL of cyclohexane were added. The mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. The mixture was heated to 150°C and polymerization was performed for 105 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 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 a polymer (P7) having a structure represented by the following formula (P7). The yield was 90%. The Mn of the polymer (P7) measured in the same manner as in Comparative Example 1 was 51,000, the Mw was 110,000, and the Mw / Mn was 2.2.

[0204] [In formula (P7), M represents Na, K, or H, and n represents a positive number (approximately 30).]

[0205] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 6 (an electrolyte membrane made of proton-substituted polymer (P7)) was obtained in the same manner as in Example 1, except that polymer (P7) was used instead of polymer (P2). The thickness of the electrolyte membrane was 27 μm.

[0206] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 199 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.12 × 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry state and the wet state by SAXS measurement was 3.7 nm and 5.5 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in the dry state and the wet state. The volume swelling ratio was 47%, confirming that the polymer electrolyte membrane of this example has excellent swelling resistance.

[0207] Comparative Example 3 (Synthesis of Polymer (P8)) 0.498 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 0.532 g of [1,1'-biphenyl]-4,4'-diol, 1.026 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.185 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Subsequently, 10 mL of DMSO and 10 mL of cyclohexane were added. The mixture was heated to 130°C and refluxed for dehydration for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 72 hours while still heated at 130°C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 300 mL of isopropyl alcohol (IPA), and a solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P8) having a structure represented by the following formula (P8). The yield was 94%. The Mn of the polymer (P8) measured in the same manner as in Comparative Example 1 was 26,000, the Mw was 69,000, and the Mw / Mn was 2.7.

[0208] [In formula (P8), M represents Na, K, or H, l is about 0.39 (0.35 or more and 0.43 or less), m is about 0.61 (0.57 or more and 0.65 or less), and n is about 40 (15 or more and 100 or less)]

[0209] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Comparative Example 3 (an electrolyte membrane made of proton-substituted polymer (P8)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P8). The thickness of the polymer electrolyte membrane was 48 μm.

[0210] (Evaluation) The polymer electrolyte membrane of this comparative example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) in the same manner as in Comparative Example 1. The proton conductivity was 113 mS / cm (80°C, relative humidity 100%), and the hydrogen gas permeability was 0.18 × 10 －７ cm ３ mm / (cm ２The volume swelling ratio was 167%.

[0211] Example 7 Synthesis of Polymer (P9) 0.985 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.157 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.668 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Then, 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 extracted from the Dean-Stark tube. Polymerization was performed for 72 hours while heating at 130°C. Then, 0.004 g of decafluorobiphenyl was added, and polymerization was performed for 3.5 hours while heating at 130°C. The reaction solution was allowed to cool to room temperature, and then reprecipitation purification was performed from 300 mL of isopropyl alcohol (IPA), and the solid was collected by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P9) containing a plurality of polymer units containing a structure represented by formula (P2) and having a decafluorobiphenyl-derived crosslinking group bonded to three or more of the polymer units. The yield was 81.9%. The Mn of polymer (P9) measured in the same manner as in Comparative Example 1 was 54,000, the Mw was 150,000, and the Mw / Mn was 2.8.

[0212] (Measurement of Fluorine Content) The fluorine content of polymer (P9) was measured by the following method. First, combustion gas generated by burning a sample (polymer (P9)) was blown into an aqueous hydrogen peroxide solution, and the fluorine content was absorbed into the aqueous solution to obtain an absorbing solution. Next, the same operation was performed without adding a sample to obtain a blank absorbing solution. The fluorine content was quantified by ion chromatography (IC) measurement using the obtained absorbing solution, the blank absorbing solution, and the original solution of the absorbing solution. The fluorine content of polymer (P9) was 0.1 mass% or less.

[0213] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 7 (an electrolyte membrane made of proton-substituted polymer (P9)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P9). The thickness of the electrolyte membrane was 62 μm.

[0214] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 200 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.13 × 10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry state and the wet state by SAXS measurement was 4.0 nm and 5.0 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in the dry state and the wet state. The volume swelling ratio was 60%, confirming that the polymer electrolyte membrane of this example has excellent swelling resistance.

[0215] Example 8 Synthesis of Polymer (P10) 2.955 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 3.526 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 2.051 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Then, 30 mL of dimethyl sulfoxide (DMSO) and 30 mL of cyclohexane were added. After heating to 130°C and reflux dehydration for 4 hours, the cyclohexane was extracted from the Dean-Stark tube. Polymerization was performed for 72 hours while heating at 130°C. After that, the temperature was lowered to room temperature, and 0.014 g of decafluorobiphenyl was added, and the mixture was heated to 130°C and polymerized for 3.5 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 1000 mL of isopropyl alcohol (IPA), and the solid was collected by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P10) containing a plurality of polymer units containing a structure represented by formula (P2) and having a decafluorobiphenyl-derived crosslinking group bonded to three or more of the polymer units. The yield was 79.3%. The Mn of the polymer (P10) measured in the same manner as in Comparative Example 1 was 71,000, the Mw was 200,000, and the Mw / Mn was 2.8. The fluorine content of the polymer P (10) measured in the same manner as in Example 7 was 0.1% by mass or less.

[0216] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 8 (an electrolyte membrane made of proton-substituted polymer (P10)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P10). The thickness of the electrolyte membrane was 56 μm.

[0217] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 221 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.12 × 10 －７ cm ３ mm / (cm ２.s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry state and the wet state by SAXS measurement was 4.0 nm and 4.9 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in the dry state and the wet state. The volume swelling ratio was 58%, confirming that the polymer electrolyte membrane of this example has excellent swelling resistance.

[0218] Example 9 Synthesis of Polymer (P11) 0.982 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.139 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.442 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Then, 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 extracted from the Dean-Stark tube. Polymerization was performed for 72 hours while heating at 130°C. After that, the temperature was lowered to room temperature, and 0.004 g of decafluorobiphenyl was added, and the mixture was heated to 130°C and polymerized for 3.5 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 300 mL of isopropyl alcohol (IPA), and the solid was collected by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P11) containing a plurality of polymer units having a structure represented by formula (P2) and having a decafluorobiphenyl-derived crosslinking group bonded to three or more of the polymer units. The yield was 78.3%. The Mn of the polymer (P11) measured in the same manner as in Comparative Example 1 was 48,000, the Mw was 230,000, and the Mw / Mn was 4.8. The fluorine content of the polymer P (11) measured in the same manner as in Example 7 was 0.1% by mass or less.

[0219] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Example 9 (an electrolyte membrane made of proton-substituted polymer (P11)) was obtained in the same manner as in Example 1, except that polymer (P2) was replaced with polymer (P11). The thickness of the electrolyte membrane was 25 μm.

[0220] (Evaluation) The polymer electrolyte membrane of this example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) using the same methods as those used in Comparative Example 1. The proton conductivity was 203 mS / cm (80°C, 100% relative humidity), confirming that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.16×10 －７ cm ３ mm / (cm ２ .s.kPa) (80°C, relative humidity 60%), and the polymer electrolyte membrane of this example is Nafion ＴＭ It was confirmed that the polymer electrolyte membrane of this example has better gas barrier properties than NR211. The lattice spacing d in the dry state and the wet state by SAXS measurement was 4.0 nm and 4.9 nm, respectively, confirming that the polymer electrolyte membrane of this example has a microphase-separated structure in the dry state and the wet state. The volume swelling ratio was 55%, confirming that the polymer electrolyte membrane of this example has excellent swelling resistance.

[0221] Comparative Example 4 (Synthesis of Polymer (P12)) 1.004 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.182 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, 0.004 g of decafluorobiphenyl, and 0.673 g of potassium carbonate were added to a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen substitution was performed. Subsequently, 10 mL of dimethyl sulfoxide (DMSO) and 10 mL of cyclohexane were added. The mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 72 hours while still heated at 130°C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed from 300 mL of isopropyl alcohol (IPA), and the solid was collected by suction filtration. The collected solid was washed with water and dried under reduced pressure to obtain a polymer (P12) having a crosslinked structure. The yield was 59.2%. The Mn, Mw, and Mw / Mn of polymer (P12) measured in the same manner as in Comparative Example 1 were 47,000, 200,000, and 4.3, respectively. In this synthesis example, the crosslinking agent decafluorobiphenyl was reacted simultaneously with the hydrophilic monomer (M1) and the hydrophobic monomer (M2). Therefore, polymer (P12) has a structure in which structural units derived from the hydrophilic monomer (M1), structural units derived from the hydrophobic monomer (M2), and crosslinkable groups derived from decafluorobiphenyl are randomly arranged.

[0222] (Preparation of Electrolyte Membrane) A polymer electrolyte membrane of Comparative Example 4 (an electrolyte membrane made of proton-substituted polymer (P12)) was obtained in the same manner as in Example 1, except that polymer (P12) was used instead of polymer (P2). The thickness of the polymer electrolyte membrane was 63 μm.

[0223] (Evaluation) The polymer electrolyte membrane of this comparative example was subjected to various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) in the same manner as in Comparative Example 1. The proton conductivity was 179 mS / cm (80°C, relative humidity 100%), and the hydrogen gas permeability was 0.11 × 10 －７ cm ３ mm / (cm ２.s.kPa) (80°C, relative humidity 60%). In the SAXS measurement, no clear scattering peaks were observed in either the dry or wet state. The volume swelling ratio was 81%. By comparing Example 7 with Comparative Example 4, it was confirmed that crosslinking at the polymer terminals improves the swelling suppression effect and proton conductivity due to crosslinking compared to polymers in which the crosslinks are spaced randomly.

[0224]

[0225] This application is based on a Japanese patent application filed on March 30, 2023 (Patent Application No. 2023-55171) and a Japanese patent application filed on January 29, 2024 (Patent Application No. 2024-11288), the entire contents of which are incorporated by reference. In addition, all references cited herein are incorporated in their entirety.

Claims

1. The polymer comprises a plurality of polymer units each having a structure represented by the following formula (1): A polymer having a crosslinking group linking three or more of said polymer units. 【Chemistry 1】 [In formula (1), A １ represents a structural unit represented by the following formula (a1): A ２ represents a structural unit represented by the following formula (a2): L １ and L ２ each independently represents a single bond, —O—, —S—, or —SO ２ - indicates n represents an integer from 10 to 100; * indicates a bond. Multiple A's １ are identical to each other, Multiple A's ２ are identical to each other, Multiple L １ may be the same or different, Multiple L ２ may be the same or different. 【Chemistry 2】 [In formula (a1), IExG represents an ion exchange group; L ３ represents a single bond, -O-, -S-, or -SO ２ - or -CO-, x represents an integer from 2 to 10; * indicates a bond. The multiple IExGs may be the same or different from each other, Multiple L ３ may be the same or different. 【Chemistry 3】 [In formula (a2), Ar represents an arylene group having no ion exchange group; L ４ represents a single bond, -O-, -S-, or -SO ２ - or -CO-, y represents an integer from 3 to 20; * indicates a bond. A plurality of Ar may be the same or different, Multiple L ４ may be the same or different.

2. Said L １ , said L ２ , said L ３ and the L ４ each independently represents a single bond or -SO ２ The polymer of claim 1, wherein

3. 3. The polymer according to claim 1, wherein the constitutional unit represented by formula (a1) contains, as the ion exchange group, at least one selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group.

4. 3. The polymer according to claim 1, wherein the constitutional unit represented by formula (a2) contains, as the arylene group, at least one selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group.

5. 3. The polymer according to claim 1, having a number average molecular weight of from 20,000 to 300,000.

6. A polymer described in claim 1 or 2, wherein the polymer unit is a polymer of a compound represented by the following formula (b1) and a compound represented by the following formula (b2) or an oxide thereof: 【Chemistry 4】 [In formula (b1), A １ is as defined above, and X １ｂ and X ２ｂ each independently represents a halogen atom. 【Chemistry 5】 [In formula (b2), A ２ is as defined above, and Z １ｂ and Z ２ｂ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

7. the bridging group has one or more aromatic rings, The polymer of claim 1 or 2, wherein the polymer units are attached to the aromatic ring.

8. 3. The polymer of claim 1, wherein the ratio of weight average molecular weight to number average molecular weight is from 2.0 to 20.

0.

9. An electrolyte material comprising the polymer according to claim 1 or 2.

10. An electrolyte membrane comprising the polymer according to claim 1 or 2.

11. A catalyst layer-coated electrolyte membrane comprising the electrolyte membrane according to claim 10 and a catalyst layer disposed on one or both sides of the electrolyte membrane.

12. A membrane electrode assembly comprising the electrolyte membrane according to claim 10 and an electrode layer disposed on one or both sides of the electrolyte membrane.

13. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 12.

14. A solid polymer water electrolysis apparatus comprising the membrane electrode assembly according to claim 12.

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