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

Abstract

To provide a polymer that exhibits superior proton conductivity as an electrolyte.SOLUTION: The present invention provides a polymer with a structure represented by a formula (1): [A1 and A2 each denote (a1) an aromatic group with an ion exchange group and (a2) an aromatic group without ion exchange groups, L1 and L2 independently denote a single bond or the like, and n denotes an integer of 10-100], wherein the polymer is a reaction product of a polymer or the like of a compound of a formula (b1) and a compound of a formula (b2) and a compound with three or more groups that react with and crosslink the polymer or the like. [A1 is defined as above, X1b and X2b independently denote a halogen atom]. [A2 is defined as above, Z1b and Z2b independently denote a hydroxy group or the like].SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to polymers, electrolyte materials, electrolyte membranes, electrolyte membranes with catalyst layers, membrane electrode assemblies, polymer electrolyte fuel cells, and polymer electrolyte water electrolyzers.

Background Art

[0002] In recent years, fuel cells have attracted attention as new energy technologies with high energy efficiency against the backdrop of environmental issues. Among them, polymer electrolyte fuel cells using polymer (macromolecule) materials as electrolytes have a high maximum current density and operate at low temperatures, making them suitable as power sources for mobile applications such as automobiles and small-capacity power sources for portable electronic devices, and are particularly noteworthy. Furthermore, from the perspective of carbon neutrality, the utilization of polymer electrolyte hydrogen energy applying fuel cell technology has also attracted attention.

[0003] As polymers (electrolyte polymers) used in the electrolytes of polymer electrolyte fuel cells and water electrolysis, fluorine-based polymers are known (see, for example, Patent Document 1). Although fluorine-based polymers are widely used in electrolyte applications because they have high proton conductivity, they have problems of high cost and large environmental impact.

[0004] For these reasons, the development of electrolyte polymers that do not use fluorine is also underway. For example, Patent Document 2 discloses an invention related to a polymer electrolyte membrane composed of a block copolymer containing at least one segment (A1) containing an ionic group and at least one segment (A2) not containing an ionic group.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

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

[0007] One aspect of the present disclosure aims to provide a polymer excellent in proton conductivity as an electrolyte. Means for Solving the Problems

[0008] The present disclosure provides the following [1] to

[16] in some aspects.

[0009] [1] A polymer having a structure represented by the following formula (1).

Chemical formula

Chemical formula

[0010] [2] The L 1 , the L 2 , the L 3 and the L 4 are each independently a single bond or -SO2-, the polymer according to [1].

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

[0012] [4] The polymer according to any one of [1] to [3], wherein the structural unit represented by the formula (a2) contains at least one selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group as the arylene 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 or an oxide thereof of a compound represented by the following formula (b1) and a compound represented by the following formula (b2). [Chemical formula] [In the formula (b1), A 1 has the same meaning as described above, and X 1b and X 2b each independently represent a halogen atom. [Chemical formula] [In the formula (b2), A 2 has the same meaning as described above, and Z 1b and Z 2b each independently represent 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], containing a plurality of polymer units containing the structure represented by the formula (1), and having a crosslinking group that binds 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] 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 reaction product of the polymer or the oxide thereof with a compound having three or more groups that react to form a crosslink, the polymer according to [7] or [8]. [Chemical formula] [In formula (b1), A 1 has the same meaning as described above, and X 1b and X 2b each independently represent a halogen atom.] [Chemical formula] [In formula (b2), A 2 has the same meaning as described above, and Z 1b and Z 2b each independently represent 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] .[[]END]]

[0020]

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

[10] .[[]END]]

[0021]

[13] An electrolyte membrane with a catalyst layer, 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 an electrode layer disposed on one or both surfaces of the electrolyte membrane.

[0023]

[15] A solid polymer fuel cell comprising the membrane electrode assembly described in

[14] .

[0024]

[16] A solid polymer water electrolyzer comprising the membrane electrode assembly described in

[14] . [Advantages of the Invention]

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

[0026]

Figure 1

[0027] Hereinafter, exemplary embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments. In this specification, the numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. Also, unless specifically specified, the units of the numerical values described before and after "~" are the same. Also, the individually described upper and lower limit values can be arbitrarily combined.

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

[0029] [Chemical Formula]

[0030] In formula (1), A 1 is a structural unit represented by the following formula (a1) (hereinafter, "structural unit A" 1(also referred to as ") and represents A 2 is a structural unit represented by the following formula (a2) (hereinafter, "structural unit A 2 (also referred to as ").) and represents L 1 and L 2 each independently represents a single bond, -O-, -S-, or -SO2-, n represents an integer from 10 to 100, and * represents a bond. A plurality of A 1 are identical to each other, a plurality of A 2 are identical to each other, a plurality of L 1 may be identical to or different from each other, and a plurality of L 2 may be identical to or different from each other.

[0031] [Chemical formula]

[0032] In formula (a1), IExG represents an ion exchange group, and L 3 represents a single bond, -O-, -S-, -SO2-, or -CO-, x represents an integer from 2 to 10, and * represents a bond. A plurality of IExG may be identical to or different from each other, and a plurality of L 3 may be identical to or different from each other.

[0033] [Chemical formula]

[0034] In formula (a2), Ar represents an arylene group having no ion exchange group, and L 4 represents a single bond, -O-, -S-, -SO2-, or -CO-, y represents an integer from 3 to 20, and * represents a bond. A plurality of Ar may be identical to or different from each other, and a plurality of L 4 may be identical to or different from each other.

[0035] Polymer (P) is a so-called electrolyte polymer and has excellent proton conductivity. Therefore, the membrane (polymer electrolyte membrane) formed by polymer (P) exhibits excellent proton conductivity. The reason why polymer (P) has excellent proton conductivity is not clear, but it has a plurality of hydrophilic structural units A that are identical to each other 1 (hydrophilic part) and a plurality of hydrophobic structural units A that are identical to each other 2 (hydrophobic part) are precisely arranged. Therefore, the ion exchange groups are arranged at equal intervals, and it is presumed that the ion exchange groups self-assemble in a higher-order structure to induce a microphase separation structure. As a result, it is presumed that a good proton conduction path is formed in polymer (P). In addition, it is also presumed that the presence of three or more ion exchange groups densely in structural unit A 1 also contributes to the improvement of phase separability and proton conductivity. The above effects are particularly remarkable in a high-humidity environment (for example, under a humidity of 80% RH or more).

[0036] Polymer (P) also tends to have excellent gas barrier properties when formed into a membrane. The reason is presumed as follows. Since the main chain of polymer (P) is composed of an arylene group containing a benzene ring, the solubility of hydrogen and oxygen is low, and the segmental motion is restricted, suppressing gas diffusion in the membrane. Therefore, it is considered to have excellent gas barrier properties when formed into a membrane.

[0037] (Polymer (P)) As represented by formula (1), polymer (P) has a repeating structure (the structure within [ ] in formula (1)) in which structural unit A 1 and structural unit A 2 are continuous via a linking group (L 1 or L 2 ). The repeating number (n) of the structure is 10 to 100, and it 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, it tends to have excellent gas barrier properties, and when the repeating number (n) is 50 or less, it tends to have excellent solubility in a solvent and film-forming properties. The repeating number (n) of the structure is preferably 15 to 80, and more preferably 20 to 50.

[0038] [Constituent unit A 1 Constituent unit A 1 has a structure in which aromatic rings having ion exchange groups (IExG) are continuous via a linking group (L 3 ).

[0039] The ion exchange group, also called an ionic group, has the property of being able to exchange ions with other ions by releasing an ion (for example, a cation). Examples of the ion exchange group include a sulfone group, an alkylsulfone group, a perfluoroalkylsulfone group, a sulfonimide group, a phosphonic acid group, a phosphoric acid group, and a carboxy group. Note that these ion exchange groups include those that are in the form of salts. For example, the "sulfone group" is -SO3M 1 / q (M represents H or a metal (for example, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Al, Fe, Pt, Rh, Ru, Ir, Pd), and q represents the valence of M (for example, an integer from 1 to 4)). The metal represented by M exists as an ion (cation) and forms a salt with -SO3 - .

[0040] The alkylsulfone group is represented by, for example, -R 1 SO3M 1 / q . R 1 is an alkanediyl group, and the number of carbon atoms thereof is preferably 1 to 12. Specific examples of R 1 include, for example, a methylene group, a butane-1,4-diyl group, and a hexane-1,6-diyl group. M and q have the same meanings as described above.

[0041] The sulfonimide group is represented by, for example, -SO2NM 1 / q SO2R 2 . R 2 is an alkyl group, and the number of carbon atoms thereof is preferably 1 to 6. Specific examples of R 2 include a methyl group, an ethyl group, and a propyl group. M and q have the same meanings as described above.

[0042] Constituent unit A 1 ​From the viewpoint of obtaining better proton conductivity, it is preferable that the ion exchange group contains at least one group selected from the group consisting of a sulfone group, an alkylsulfone group, and a sulfonimide group, and it is more preferable that it contains a sulfone group. From the same viewpoint, the constituent unit A 1 Among the plurality of ion exchange groups present in it, it is more preferable that the majority of them are in the above preferred embodiment, and the constituent unit A 1 It is particularly preferable that all of the plurality of ion exchange groups present in it are in the above preferred embodiment.

[0043] The constituent unit A 1 From the viewpoint of obtaining better proton conductivity, as the linking group (L 3 ), it is preferable to contain at least one group selected from the group consisting of -SO2- and -CO-, and it is more preferable to contain -SO2-. From the same viewpoint, the constituent unit A 1 Among the plurality of linking groups (L 3 ) present in it, it is more preferable that the majority of them are in the above preferred embodiment.

[0044] The constituent unit A 1 The linking group (L 3 ) in it is preferably a single bond or -SO2- from the viewpoint of achieving both better proton conductivity and chemical durability.

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

[0046] The constituent unit A 1 The repeating number (x) of the structure within [ ] in the formula (a1) in it is preferably 2 to 8, and more preferably 3 to 5, from the viewpoint of obtaining better proton conductivity and excellent heat and water resistance.

[0047] The constituent unit A1 From the viewpoint of obtaining better proton conductivity, it preferably contains at least one structure selected from the group consisting of the structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)") and the structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)").

[0048]

Chemical formula

[0049]

Chemical formula

[0050] IExG and * in formula (a1-1) and formula (a1-2) have the same meanings as described above. A plurality of IExGs may be the same as or different from each other. x in formula (a1-1) 1 represents an integer from 2 to 10, and x in formula (a1-2) 2 represents an integer from 2 to 5. However, when the constitutional unit A 1 contains both structure (a1-1) and structure (a1-2), the sum of x 1 and 2x 2 is from 2 to 10. x 1 is preferably from 2 to 5, more preferably from 2 to 3. x 2 is preferably from 2 to 3, more preferably 2.

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

[0052] Constituent unit A 1 Specific examples thereof include constituent units represented by the following formulas (A1-1) to (A1-4).

[0053]

Chemical formula

[0054] IExG and * in formulas (A1-1) to (A1-4), and L in formulas (A1-3) to (A1-4) 3 have the same meanings as described above. A plurality of IExG may be the same as or different from each other, and a plurality of L 3 may be the same as or different from each other.

[0055] Constituent unit A in polymer (P) 1 is preferably any of the constituent units represented by formulas (A1-1) to (A1-4) from the viewpoint of obtaining more excellent proton conductivity and excellent chemical durability, and more preferably is the constituent unit represented by formula (A1-2).

[0056] [Constituent unit A 2 Constituent unit A 2 has a structure in which an arylene group (Ar) having no ion-exchange group is continuous via a linking group (L 4 ).

[0057] The arylene group is a divalent aromatic hydrocarbon group and has a structure in which two hydrogen atoms are removed from an aromatic hydrocarbon. The number of aromatic rings in the arylene group is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1 from the viewpoints of solubility in a solvent and film-forming property. 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 anthracenylene group, a phenanthrylene group, a triphenylene group, a pyrenylene group, and a tetracenylene group.

[0059] Constituent unit A 2 From the viewpoints of solubility in a solvent and film-forming properties, the arylene group preferably contains 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. From the same viewpoint, among the plurality of arylene groups present in the constituent unit A 2 it is more preferable that the majority of them are in the above preferable form, and among the plurality of arylene groups present in the constituent unit A 2 it is particularly preferable that all of them are independently a phenylene group, a naphthylene group, or a fluorene group.

[0060] Constituent unit A 2 From the viewpoints of excellent solubility in a solvent, excellent film-forming properties, and excellent mechanical strength during film formation, the linking group (L 4 ) preferably contains at least one group selected from the group consisting of -SO2-, -CO-, and a single bond, and more preferably contains -SO2- or -CO-. From the same viewpoint, among the plurality of linking groups (L 2 ) present in the constituent unit A 4 it is more preferable that the majority of them are in the above preferable form, and all of the plurality of linking groups (L 2 ) present in the constituent unit A 4 may also be in the above preferable form.

[0061] Constituent unit A 2 The linking group (L 4 ) in is preferably a single bond or -SO2- from the viewpoint of excellent chemical durability.

[0062] Constituent unit A 2In the formula (a2), the number of repetitions (y) of the structure within the brackets is preferably 4 to 12, more preferably 5 to 10, from the viewpoint of obtaining better proton conductivity and excellent heat and water resistance.

[0063] Constituent unit A 2 In the formula (a2), the number of repetitions (y) of the structure within the brackets is preferably a number 2 to 7 more than the number of repetitions (x) of the structure within the brackets in the formula (a1) (x+(2 to 7)), from the viewpoint of achieving both better proton conductivity and heat and water resistance.

[0064] Constituent unit A 2 Preferably includes at least one structure selected from the group consisting of the structure represented by the following formula (a2-1) and the structure represented by the following formula (a2-2), from the viewpoints of excellent solubility in a solvent, film-forming properties, and mechanical strength during film formation.

[0065]

Chemical formula

[0066]

Chemical formula

[0067] In the formulas (a2-1) and (a2-2), Ar and * have the same meanings as described above. A plurality of Ars may be the same as or different from each other.

[0068] Constituent unit A 2 Specific examples thereof include a constituent unit represented by the following formula (A2).

[0069]

Chemical formula

[0070] Ar, L 4 and * have the same meanings as described above, Q represents a group of the structure represented by the formula (a2-1) or the formula (a2-2), and y1 and y 2 each independently represents an integer of 2 to 4. y 1 and y 2 is preferably 2 to 3. The plurality of Ar's may be the same as or different from each other, and the plurality of L 4 may be the same as or different from each other.

[0071] [Linking group] From the viewpoint of obtaining better proton conductivity and better chemical durability, the polymer (P) has a linking group (L 1 between the constituent unit A 2 and the constituent unit A 1 or L 2 ) preferably contains at least one group selected from the group consisting of a single bond, -SO2- and -S-, and more preferably contains -SO2-. From the same viewpoint, a plurality of constituent units A present in the polymer (P 1 between the constituent unit A 2 and the constituent unit A 1 and L 2 ) are more preferably in the above preferred form for the majority of them, and all of the linking groups (L 1 between the plurality of constituent units A present in the polymer (P 2 and the constituent unit A 1 and L 2 ) being in the above preferred form is particularly preferred.

[0072] The linking group (L 1 between the constituent unit A 2 and the constituent unit A 1 and L 2 ) in the polymer (P) is preferably each independently a single bond or -SO2- from the viewpoint of obtaining better proton conductivity and better chemical durability.

[0073] As described above, the polymer (P) has, in addition to the linking group (L 1 between the constituent unit A 2 and the constituent unit A 1 and L 2 ), in the constituent unit A 1 and in the constituent unit A2 Among them, the linking groups (L 3 and L 4 ) are included. From the viewpoint of obtaining more excellent proton conductivity and excellent chemical durability, these linking groups (L 1 , L 2 , L 3 and L 4 ) are each independently particularly preferably a single bond or -SO2-.

[0074] The polymer (P) may be composed of a structure represented by the 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]

Chemical formula

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

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

[0078] Polymer unit A has a structure obtained by removing terminal groups Z 1 and Z 2 from any of the compounds represented by the above formulas (1-1) to (1-3). Of the two terminal groups of polymer unit A, the terminal group that binds to the crosslinking group may be A 1 or may be A 2 . When the terminal group that binds to the crosslinking group is a single bond represented by L 2 (that is, L 2 that binds to Z 2 in formulas (1-1) and (1-2)), the terminal group that binds to the crosslinking group is regarded as A 2 . The two terminal groups of polymer unit A may each bind to a different crosslinking group. Of the two terminal groups of polymer unit A, the terminal group on the side opposite to the terminal group that binds to the crosslinking group may bind to either of the above terminal groups Z 1 and Z 2 . The plurality of polymer units A that bind to one crosslinking group may be the same as or different from each other.

[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 above polymer unit A is bonded to the aromatic ring of the crosslinking group. Polymer unit A may be directly bonded to the aromatic ring or may be bonded to the aromatic ring via -O-, -S- or -SO2-. The number of aromatic rings of the crosslinking group is preferably 1 or 2.

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

[0081]

Chem.

[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, and L 5 represents a single bond, -O-, -S-, -SO2-, or -CO-, and L 6 represents a single bond, -O-, -S-, or -SO2-, * represents a bond that binds to polymer unit A, p, q, r, and s each represent an integer from 0 to 5, and z represents 0 or 1. However, p + q is 3 or more, p + r is from 0 to 5, q + s is from 0 to 5, and when z is 0, r and p are 0. When there are a plurality of Es, the plurality of Es may be the same as or different from each other. When there are a plurality of L 5 s, the plurality of L 5 s may be the same as or different from each other. The plurality of L 6 s may be the same as or different from each other.

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

[0084]

Chem.

[0085] The number of crosslinking groups contained in the crosslinked polymer (P') may be one or a plurality. The plurality of crosslinking groups may be the same as or different from each other.

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

[0087] From the viewpoint of obtaining more excellent proton conductivity, the proportion of the structure represented by the formula (1) in the whole polymer (P) is preferably 80% by mass or more. From the same viewpoint, the proportion of the structure represented by the formula (1) in the whole polymer (P) may be 85% by mass or more, or 90% by mass or more. The proportion of the structure represented by the formula (1) in the whole polymer (P) may be less than 100% by mass. The proportion of the structure represented by the formula (1) in the whole polymer (P) may be 80% by mass or more and less than 100% by mass, or 85% by mass or more and less than 100% by mass.

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

[0089] From the viewpoints of excellent proton conductivity and excellent mechanical strength during film formation, 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 viewpoints of excellent solubility in a solvent and excellent film formability, it may be 300,000 or less, 200,000 or less, or 150,000 or less. 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] From the viewpoints of excellent proton conductivity and excellent mechanical strength during film formation, 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 viewpoints of excellent solubility in a solvent and excellent film formability, it may be 500,000 or less, 300,000 or less, or 200,000 or less. 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, and may be 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. The polydispersity of the polymer (P) may be 20.0 or less, and may be 15.0 or less, or 10.0 or less, from the viewpoint of solubility in a solvent. 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 the weight-average molecular weight of the polymer (P) are values in terms of standard polyethylene glycol / oxide (PEG / PEO) measured by gel permeation chromatography (GPC).

[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)") and 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]

Chemical formula

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

[0096]

Chemical formula

[0097] In formula (b2), A 2 has the same meaning as described above, and Z 1b and Z2b 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 of the halogen atom, the alkylborane group and the boronic acid ester group represented by Z 1 and Z 2 described above.

[0098] In the above method, a structure (repeating structure) in which the structural unit A 1 and the structural unit A 2 are alternately arranged can be formed throughout the polymer. Therefore, according to the above method, the repeating number n in the formula (1) can be easily set to 10 or more.

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

[0100] As the compound (b1), a plurality of compounds in which X 1b and / or X 2b are different can be used. Similarly, as the compound (b2), a plurality of compounds in which Z 1b and / or Z 2bA plurality of different types of compounds can be used.

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

[0102] As the solvent used in the reaction, a good solvent for compound (b1), compound (b2), and polymer (P) and capable of increasing the molecular weight of polymer (P) during polymerization is preferable. For example, N-methyl-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethyl urea 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 the 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 the solvent that can be used in the reaction are the same as those of the solvent that can be used in the above aromatic nucleophilic substitution reaction.

[0106] The catalyst is not particularly limited as long as it can promote the 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, conventionally known catalysts (such as palladium catalysts and nickel catalysts) used in the Suzuki-Miyaura coupling reaction can be used.

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

[0108] Examples of the nickel catalyst 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 the decomposition of the polymer, the reaction temperature is preferably 300°C or lower, more preferably 250°C or lower.

[0111] In the above aromatic nucleophilic substitution reaction and cross-coupling reaction, in order to increase the molecular weight of the polymer (P), it is preferable to remove water from the reaction system. The method of dehydration is not particularly limited. For example, a method of azeotropic dehydration by coexisting an azeotropic solvent in the reaction system, a method of heating above the boiling point of water and continuously removing it outside the reaction system, a method of coexisting a water absorbent such as molecular sieve, etc. can be used. The azeotropic solvent is not particularly limited as long as it can remove water, and examples thereof include benzene, toluene, cyclohexane, and xylene.

[0112] The above aromatic nucleophilic substitution reaction and cross-coupling reaction are preferably carried out under an inert atmosphere (for example, 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. As a method for recovering the polymer from the reaction solution, for example, a method of adding the reaction solution to a solvent in which the solubility of the polymer is low and precipitating the polymer as a solid for recovery, and a method of removing the solvent from the reaction solution by evaporation and recovering the polymer as a solid can be mentioned. As a method for purifying the polymer, for example, a method of washing in a solvent in which the solubility of the polymer is low and the solubility of by-produced inorganic salts and compounds derived from residual monomers is high, and a washing method using a Soxhlet extractor can be mentioned. 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 the formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, the polymer (P) is among the polymers having a structure represented by the formula (1), L 1 , L 2 , L 3 or L 4 can be an oxide of a polymer containing -S- (sulfide group) as L (hereinafter referred to as "sulfide-containing polymer"). From the viewpoint of excellent chemical durability, among the polymers having a structure represented by the formula (1), L 1 , L 2 , L 3 and L4 is preferably a polymer which is, independently of each other, a single bond, -S- or -SO2-.

[0114] The method for oxidizing the sulfide-containing polymer is not particularly limited, and may be a known method for oxidizing a sulfide group (-S-) to obtain a sulfonyl group (-SO2-). Examples of such a method include immersing the sulfide-containing polymer 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% by mass. The concentration of sulfuric acid in the mixed solution may be, for example, 5 to 25% by mass. The concentration of hydrogen peroxide in the mixed solution may be, for example, 1 to 15% by 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] Among the polymers having the structure represented by the formula (1), the polymer (P) obtained by the above method is L 1 , L 2 , L 3 or L 4 is a polymer containing -SO2- (sulfonyl group) as L. The polymer may be one in which all of the sulfide groups in the sulfide-containing polymer are oxidized to sulfonyl groups (complete oxide), or may be one in which a part of the sulfide groups in the sulfide-containing polymer are 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 the compound (b1) and the compound (b2) or an oxide thereof with a compound having three or more groups that react with the polymer or an oxide thereof to form a crosslink (hereinafter also referred to as "crosslinkable compound (d)"). That is, the polymer (P) can be a reaction product of a polymer of the compound (b1) and the compound (b2) or an oxide thereof and the crosslinkable compound (d).

[0117] In the above method, a crosslinked product (for example, the above-mentioned crosslinked polymer (P’)) having a polymer or its oxide of compound (b1) and compound (b2) as polymer units can be obtained. According to the above method, a crosslinked structure can be formed while maintaining the precise sequence structure, and excellent proton conductivity and excellent swelling resistance can be achieved simultaneously.

[0118] The crosslinkable compound (d) may be a known crosslinkable compound, for example, it may be a low molecular weight compound having a molecular weight of 1000 or less. The group that reacts with the above 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 above polymer or its oxide to form a crosslink is preferably directly bonded to the aromatic ring. The number of aromatic rings possessed by 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]

Chemical formula

[0122] In formula (d), E, L 5 and z have the same meanings as described above, and t and u each represent an integer from 0 to 5. However, t + u is 3 or more, and when z is 0, t is 0. A plurality of Es may be the same as or different from each other. Among the plurality of Es, three or more Es react with the terminal groups (X 1b , X 2b , Z 1b or Z 2b ) of the above polymer or its oxide to form a crosslink.

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

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

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

[0126] Since the electrolyte material and the electrolyte membrane contain the polymer (P), they have excellent proton conductivity.

[0127] The electrolyte material and the electrolyte membrane may also have a microphase separation structure in a state of being immersed in water (wet state). Specifically, when small-angle X-ray scattering (SAXS) measurement is performed on the electrolyte membrane in a state of being immersed in water, the obtained peak plane spacing may be 4.0 nm or more.

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

[0129] The electrolyte material and the electrolyte membrane may consist only of 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% by mass, or may be 94 to 100% by mass or 97 to 100% by mass. The above content is the content based on the total solid content of the electrolyte material or the electrolyte membrane.

[0130] Examples of components other than the polymer (P) that can be included in the electrolyte material and the electrolyte membrane include water-retaining inorganic substances and radical scavengers. Specifically, for example, water, silica, cerium oxide, and manganese oxide can be mentioned. These can be used alone or in combination of multiple types.

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

[0132] The manufacturing method of the electrolyte membrane is not particularly limited, and it can be manufactured by a method known as a method for forming an electrolyte polymer into a film. Examples of the manufacturing method of the electrolyte membrane include a solution casting method, a dispersion casting method, a melt pressing method, and a melt extrusion method.

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

[0134] The solvent used in the solution casting method is not particularly limited as long as it can dissolve the polymer (P). For example, N-methyl-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethyl urea can be used. These may be used alone or in combination of two or more.

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

[0136] The dispersion medium used in the dispersion casting method is not particularly limited as long as it can disperse the polymer (P). For example, water, ethers, alcohols, ketones, acetonitrile, nitromethane, toluene, xylene, chlorobenzene, and chloroform can be used. 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 of two or more.

[0137] The electrolyte material and the electrolyte membrane are suitably used for a polymer electrolyte fuel cell and a polymer electrolyte water electrolysis device. The electrolyte material and the electrolyte membrane can also be used for a redox flow battery, an electrochemical hydrogen pump, a chlor-alkali electrolysis device, a solid acid catalyst, a membrane type humidity control device, a gas separation membrane, and the like.

[0138] The electrolyte membrane can also be used by laminating it with a microporous membrane, a non-woven fabric, a mesh, or the like. That is, another embodiment of the present disclosure is a laminate including an electrolyte membrane and another membrane (a microporous membrane, a non-woven fabric, a mesh, etc.).

[0139] <Electrolyte Membrane with Catalyst Layer> The electrolyte membrane with catalyst layer of one embodiment includes the electrolyte membrane of the above 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 for a polymer electrolyte fuel cell, a polymer electrolyte water electrolysis device, etc. Hereinafter, the layer composed of an anode catalyst is referred to as an anode catalyst layer, and the layer composed of a cathode catalyst is referred to as a cathode catalyst layer.

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

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

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

[0144] As the conductive material, for example, carbon blacks such as furnace black, ketjen black, channel black and acetylene black, activated carbon, and graphite can be used. These may be used alone or in combination of two or more kinds.

[0145] As the ionomer, a conventionally known material can be used. For example, an ionomer containing a perfluorinated electrolyte can be used. Further, the above polymer (P) can also be used as the ionomer. As the ionomer, a material having high oxygen permeability is preferably used. There is no particular limitation on the addition amount of the ionomer in the catalyst layer, but it is preferable to adjust the addition amount within a range where oxygen diffusion is not easily inhibited.

[0146] The catalyst layer may further contain, as an additive, a water repellent such as fluorinated carbon, a binder such as a fluororesin, a hydrocarbon resin having a sulfone group, and the like.

[0147] A laminate having an anode catalyst layer and a cathode catalyst layer on both sides of the electrolyte membrane (for example, 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 for a polymer electrolyte fuel cell and a polymer electrolyte water electrolysis device.

[0148] In the above embodiment, instead of the electrolyte membrane, a laminate including the other membranes (micro-porous membrane, non-woven fabric, mesh, etc.) described above can also be used.

[0149] <Membrane Electrode Assembly> A membrane electrode assembly according to an embodiment includes the electrolyte membrane of the above embodiment and an electrode layer 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 electrolyte membrane with a catalyst layer of the above embodiment. Hereinafter, an electrode layer including an anode catalyst layer is referred to as an anode layer, and an electrode layer including a cathode catalyst layer is referred to as a cathode layer.

[0151] The configuration of the electrode layer is not particularly limited, and it can 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 catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion base material. When the catalyst layer itself has gas diffusibility, the electrode layer may be composed of only the catalyst layer. As the gas diffusion base material, for example, a porous membrane can be used. As the gas diffusion base material, in addition to gas diffusibility, those having water repellency and conductivity (for example, carbon fiber base materials such as carbon nonwoven fabric and carbon paper, titanium fiber sintered body) can also be used.

[0152] A laminate having an anode layer and a cathode layer as electrode layers on both sides of the electrolyte membrane (for example, one having a layer configuration of "gas diffusion base material / anode catalyst layer / electrolyte membrane / cathode catalyst layer / gas diffusion base material") is also called an MEA (Membrane Electrode Assembly) and is suitably used for a polymer electrolyte fuel cell and a polymer electrolyte water electrolysis device.

[0153] In the above embodiment, instead of the electrolyte membrane, a laminate including the other membranes (micro-porous membrane, non-woven fabric, mesh, etc.) described above can also be used.

[0154] <Polymer electrolyte fuel cell> A polymer electrolyte fuel cell according to 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 it can be a conventionally known configuration except for using the membrane electrode assembly of the above embodiment. The polymer electrolyte fuel cell may include, for example, two or more membrane electrode assemblies. Two or more membrane electrode assemblies may be stacked via a separator. As the separator, those conventionally known as separators for polymer electrolyte fuel cells can be used.

[0156] <Polymer electrolyte water electrolysis device> The proton exchange membrane water electrolysis device according to one embodiment includes the membrane electrode assembly of the above embodiment.

[0157] The configuration of the proton exchange membrane water electrolysis device is not particularly limited, and it can be a conventionally known configuration except that the membrane electrode assembly of the above embodiment is used. The proton exchange membrane water electrolysis device may, for example, further include a current collector outside the membrane electrode assembly. Also, two or more membrane electrode assemblies may be provided.

Example

[0158] Hereinafter, the content of the present disclosure will be described in more detail 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, charged with 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of dehydrated tetrahydrofuran, and stirring was started. It was cooled to -70 °C in a methanol-dry ice bath, and 320 mL of a 2.6 mol / L normal butyllithium-hexane solution was added dropwise. Stirring was carried out for 1 hour while cooling with the bath. 40 mL of sulfurous acid gas was introduced into the flask with nitrogen gas. Stirring was carried out for 30 minutes while cooling with the bath. Then, the bath was removed and the internal temperature was raised to 0 °C. The precipitated solid was separated by suction filtration and washed with 200 mL of tetrahydrofuran. The recovered solid was dissolved in 2 L of pure water, 260 mL of 35% hydrogen peroxide solution was added, and stirring was carried out for 18 hours. The solid was removed by suction filtration, and 600 g of sodium chloride was added to the recovered filtrate. The precipitated white solid was recovered 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]

Chemical formula

[0161] <Synthesis Example 2> (Synthesis of Hydrophobic Monomer (M2)) Into a 200 mL flask equipped with a stir bar, Dean-Stark tube, reflux condenser, and calcium chloride tube, 4.0 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 14.8 g of [1,1'-biphenyl]-4,4'-diol, and 13.2 g of potassium carbonate were charged, and 50 mL of N,N-dimethylacetamide (DMAc) and 50 mL of toluene were added. While stirring, the temperature was raised to 160 °C in an oil bath, and heating and stirring were continued for 4 hours. Toluene was withdrawn from the Dean-Stark tube, and the temperature was raised to 180 °C in an oil bath. After the temperature was raised, 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 separated by filtration. The solid separated by filtration was washed with 300 mL of ethanol and dried. The dried solid was purified by recrystallization from NMP / ethanol. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0162]

Chemical formula

[0163] <Synthesis Example 3> (Synthesis of Hydrophobic Monomer (M3)) A 500 mL flask equipped with a stirrer and a cooling tube was purged with nitrogen. Into this flask, 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. While stirring, the temperature was raised to 100 °C in an oil bath, and heating and stirring were 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 the eluent. The fraction containing the target product was 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] [Chemical formula]

[0165] <Synthesis Example 4> (Synthesis of Hydrophobic Monomer (M4)) A 500 mL flask equipped with a stirrer and a cooling tube was purged with nitrogen. Into this flask, 20 g of anhydrous aluminum chloride, 10 g of isophthaloyl chloride, and 240 mL of 1,2-dichlorobenzene were added. While stirring the reaction solution, 24 g of 3-bromo-1,1'-biphenyl was added dropwise. The temperature of the reaction solution was raised 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 next reaction.

[0166] 0.80 g of the obtained dry 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 while stirring vigorously, the reaction solution was heated to 50 °C. 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 and separated by liquid-liquid extraction, and the organic layer was recovered. The solvent was distilled off using an evaporator, 20 mL of ethyl acetate was added and suspended. The suspension was filtered by suction, the filtrate was recovered, and the solvent was distilled off using an evaporator to obtain an orange oily substance. The obtained oily substance was dissolved in ethyl acetate and purified by silica column chromatography using an ethyl acetate / hexane = 1 / 1 (volume ratio) mixed solvent as the developing solvent. The fraction containing the target product was recovered, and the solvent was distilled off using an evaporator. The obtained solid was purified by recrystallization from hot toluene. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M4) represented by the following formula (M4). The yield was 60%.

[0167] [Chemical formula]

[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] [Chemical formula]

[0170] <Synthesis Example 6> (Synthesis of Hydrophobic Monomer (M6)) A 500 mL flask equipped with a stir bar 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 stirring was continued for 3 hours. After allowing the reaction solution to cool to room temperature, 200 mL of water and 500 mL of ethyl acetate were added and the layers were separated, and the organic layer was recovered. The solvent was distilled off 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 the developing solvent. The fraction containing the target product was recovered, and the solvent was distilled off 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] [Chemical formula]

[0172] <Comparative Example 1> (Synthesis of Polymer (P1)) Into a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 1.334 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 0.816 g of sodium diphenyl sulfone-4,4'-dichloro-3,3'-disulfonic acid, and 0.551 g of potassium carbonate were added, and nitrogen substitution was performed. Then, 10 mL of DMAc and 10 mL of toluene were added. After heating to 160 °C and refluxing for dehydration for 4 hours, toluene was extracted from the Dean-Stark tube. Polymerization was carried out at 180 °C for 21 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P1) having the structure represented by the following formula (P1). The yield was 90%. Here, n in formula (P1) was calculated from the number average molecular weight described later. The same applies to n in formulas (P2) to (P8) described later.

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

[0174] (Molecular weight measurement) The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer (P1) were measured under the following conditions, and the polydispersity (Mw / Mn) was determined. Mn was 39000, Mw was 130000, 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. Polymer (P1) was dissolved in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L of lithium bromide) at a concentration of 1 mg / mL to prepare a sample solution. HLC-8320GPC manufactured by Tosoh Corporation was used as the apparatus. Two TSKgel SuperAWM-H (inner diameter 6.0 mm, length 15 cm) manufactured by Tosoh Corporation were used as the columns. A differential refractometer detector was used as the detector. The flow rate was 0.6 mL / min and the measurement was carried out at 40 °C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined by conversion to standard polyethylene glycol / oxide (PEG / PEO). Also, the polydispersity (Mw / Mn) was determined by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0176] (Fabrication 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 and coated on a glass substrate and dried at 60 °C for 12 hours to obtain a membrane (membrane thickness 24 μm). The membrane thickness was measured at 25 points in the plane using a PG-02 constant pressure thickness measuring instrument manufactured by TECLOCK CORPORATION, and the average value was used. The obtained membrane was immersed in 1 M hydrochloric acid for 24 hours to replace metal ions (Na + or K + ) with protons (H + ), then immersed in pure water, washed thoroughly, and dried under reduced pressure to obtain the polymer electrolyte membrane of Comparative Example 1 (an electrolyte membrane composed of proton-substituted polymer (P1), membrane thickness 24 μm).

[0177] (Evaluation) [Proton conductivity evaluation] The proton conductivity of the obtained polymer electrolyte membrane was measured by the following method. A measurement cell made of Teflon (registered trademark) (manufactured by Scribner, BT-115) was used, and the fabricated electrolyte membrane was brought into contact with four platinum wires and placed in the cell. After maintaining at a relative humidity of 70% for 2 hours, the humidity was increased from 20% relative humidity, and DC resistance measurement was performed by the four-terminal method while maintaining at the set humidity. The proton conductivity in the plane direction of the electrolyte membrane was calculated from the obtained resistance value, the film thickness of the polymer electrolyte membrane, and the distance between the terminals. The proton conductivity of the polymer electrolyte membrane in 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 according to the gas permeability test method by the isobaric method (JIS K 7126-2). Specifically, first, the polymer electrolyte membrane was mounted in a state of being hermetically sealed between two chambers of a permeation cell. Hydrogen, which is a measurement gas, was supplied to one side of the polymer electrolyte membrane, and Ar gas was supplied as a carrier gas to the other side. The relative humidity was adjusted by the humidifier temperature and cell temperature of each supply gas. The measurement gas that permeated through 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 the flow rate. From the obtained gas permeability and the film thickness of the polymer electrolyte membrane, the gas permeability (cm 3 ·mm / (cm 2 ·s·kPa) was calculated. The hydrogen gas permeability of the polymer electrolyte membrane in this comparative example was 0.71×10 -7 cm 3 ·mm / (cm 2 ·s·kPa) (80 °C, 60% relative humidity).

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

[0180] Regarding the obtained small-angle scattering profile, the peak top position q max From this, the interplanar spacing d (= 2π / q max ) was calculated. 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] [Measurement of volume swelling ratio] A 3 cm square film was punched out from the obtained polymer electrolyte membrane, and the punched-out film was immersed in 50 mL of pure water at 80 °C for 1 hour. By measuring the dimensional change before and after immersion in pure water, the volume of the membrane was calculated. 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, commercially available Nafion TM NR211 (membrane thickness 25 μm) was used, and various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed 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 ·s·kPa) (80 °C, relative humidity 60%). The interplanar spacing d in the dry state and wet state by SAXS measurement was 3.3 nm and 5.3 nm, respectively. The volume swelling ratio was 61%. In the following examples, based on the volume swelling ratio of the above Nafion TM NR211, when the volume swelling ratio was 61% or less, it was evaluated that the electrolyte membrane had excellent swelling resistance.

[0183] <Example 1> (Synthesis of polymer (P2)) Into a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 0.983 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.181 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.507 g of potassium carbonate were added, and nitrogen substitution was carried out. Then, 10 mL of dimethyl sulfoxide (DMSO) and 10 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 150 hours while heating at 130 °C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out 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 the structure represented by the following formula (P2). The yield was 97%. The Mn of the 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] [Chemical formula] [In formula (P2), M represents Na, K or H, and n represents a positive number (about 20).]

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

[0186] (Evaluation) For the polymer electrolyte membrane of this example, 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 231 mS / cm (80 °C, relative humidity 100%), and it was confirmed 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 it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. In the SAXS measurement, as shown in Figure 1, distinct peaks were confirmed in both the dry state and the wet state. The interplanar spacing d in the dry state and the wet state by SAXS measurement was 3.6 nm and 5.5 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and the wet state. The volume swelling ratio was 184%.

[0187] <Example 2> (Synthesis of Polymer (P3)) To a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 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, and nitrogen substitution was performed. Then, 25 mL of DMSO and 25 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was withdrawn from the Dean-Stark tube. Heating was carried out at 140 °C for 260 hours of polymerization. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed with 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 the polymer (P3) measured in the same manner as in Comparative Example 1 was 33000, the Mw was 75000, and the Mw / Mn was 2.3.

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

[0189] (Preparation of electrolyte membrane) An electrolyte membrane of Example 2 (an electrolyte membrane composed of a proton-substituted polymer (P3)) was obtained by the same method as in Example 1, except that polymer (P3) was used instead of polymer (P2). The membrane thickness of the polymer electrolyte membrane was 37 μm.

[0190] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed on the polymer electrolyte membrane of this example by the same method as in Comparative Example 1. The proton conductivity was 185 mS / cm (80 °C, 100% relative humidity), and it was confirmed 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, 60% relative humidity), and it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 3.9 nm and 5.4 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and wet state. 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 the polymer (P3). The obtained solution was cast onto a glass substrate and dried at 60° C. for 12 hours to obtain a film (thickness 37 μm). The obtained film 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 film was immersed in pure water, thoroughly washed, and dried under reduced pressure to obtain a film (thickness 37 μm) made of the polymer (P4) having a structure represented by the following formula (P4). The Mn of the polymer (P4) measured in the same manner as above was 37000, the Mw was 84000, and the Mw / Mn was 2.3. When the infrared absorption spectrum of the polymer film before and after the oxidation reaction was measured, it was found to have a peak at 1570 cm -1 and 1470cm -1 The absorption peak at 1330 cm disappeared after oxidation. -1 The absorption peak intensity at 1570cm increased. -1 and 1470cm -1 The absorption peak at 1330 cm is due to the ring stretching vibration of the benzene ring with the -S- bond. -1 Since the absorption peak is due to the stretching vibration of the -SO2- bond, it was confirmed that the -S- bond was oxidized to a -SO2- bond by the oxidation reaction.

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

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

[0194] (evaluation) For the polymer electrolyte membrane of this example, 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 172 mS / cm (80 °C, relative humidity 100%), and it was confirmed that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.11×10 -7 cm 3 ·mm / (cm 2 ·s·kPa) (80 °C, relative humidity 60%), and it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 3.9 nm and 5.2 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and wet state. The volume swelling ratio was 74%.

[0195] <Example 4> (Synthesis of Polymer (P5)) To a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 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, and nitrogen substitution was performed. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Heating was carried out at 140 °C for 100 hours of polymerization. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P5) having a structure represented by the following formula (P5). The yield was 85%. The Mn of the polymer (P5) measured in the same manner as in Comparative Example 1 was 28000, the Mw was 66000, and the Mw / Mn was 2.4.

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

[0197] (Fabrication of electrolyte membrane) An electrolyte membrane of Example 4 (an electrolyte membrane composed of a proton-substituted polymer (P5)) was obtained by the same method as in Example 1, except that polymer (P5) was used instead of polymer (P2). The membrane thickness of the polymer electrolyte membrane was 31 μm.

[0198] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed on the polymer electrolyte membrane of this example by the same method as in Comparative Example 1. The proton conductivity was 232 mS / cm (80 °C, relative humidity 100%), and it was confirmed 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 it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 3.4 nm and 5.2 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and wet state. The volume swelling ratio was 506%.

[0199] <Example 5> (Synthesis of polymer (P6)) Into a 100 mL three-necked flask equipped with a nitrogen introduction tube, a stirrer, and a Dean-Stark tube, 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, and nitrogen substitution was performed. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. It was heated to 150 °C and polymerized for 120 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P6) having the 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 29000, the Mw was 59000, and the Mw / Mn was 2.0.

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

[0201] (Fabrication of electrolyte membrane) An electrolyte membrane of Example 5 (an electrolyte membrane composed of a proton-substituted polymer (P6)) was obtained by the same method as in Example 1, except that polymer (P6) was used instead of polymer (P2). The membrane thickness of the electrolyte membrane was 52 μm.

[0202] (Evaluation) For the polymer electrolyte membrane of this example, various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed by the same method as in Comparative Example 1. The proton conductivity was 188 mS / cm (80 °C, relative humidity 100%), and it was confirmed that the polymer electrolyte membrane of this example had good proton conductivity. The hydrogen gas permeability was 0.11×10 -7 cm 3 ·mm / (cm 2·s·kPa) (at 80 °C and 60% relative humidity), and the polymer electrolyte membrane of this example is Nafion TM It was confirmed to have better gas barrier properties than Nafion NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 3.8 nm and 5.6 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example has a microphase separation structure in the dry state and wet state. The volume swelling ratio was 114%.

[0203] <Example 6> (Synthesis of Polymer (P7)) To a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 0.932 g of the hydrophobic monomer (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, and nitrogen substitution was performed. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was withdrawn from the Dean-Stark tube. Heating was carried out at 150 °C for 105 hours for polymerization. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out 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 51000, the Mw was 110000, and the Mw / Mn was 2.2.

[0204]

Chemical formula

[0205] (Fabrication of Electrolyte Membrane) A polymer electrolyte membrane (electrolyte membrane composed of proton-substituted polymer (P7)) of Example 6 was obtained by the same method as in Example 1 except that polymer (P7) was used instead of polymer (P2). The membrane thickness of the electrolyte membrane was 27 μm.

[0206] (Evaluation) For the polymer electrolyte membrane of this example, various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling rate measurement) were performed in the same manner as in Comparative Example 1. The proton conductivity was 199 mS / cm (80 °C, 100% relative humidity), and it was confirmed 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, 60% relative humidity), and it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry and wet states by SAXS measurement was 3.7 nm and 5.5 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry and wet states. The volume swelling rate was 47%, and it was confirmed that the polymer electrolyte membrane of this example had excellent swelling resistance.

[0207] <Comparative Example 3> (Synthesis of Polymer (P8)) In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 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, and nitrogen substitution was performed. Then, 10 mL of DMSO and 10 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 72 hours while heating at 130 °C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out 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 (P8) having the 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 26000, the Mw was 69000, and the Mw / Mn was 2.7.

[0208] [Chemical formula] [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 (electrolyte membrane composed of proton-substituted polymer (P8)) of Comparative Example 3 was obtained by the same method as in Example 1 except that polymer (P8) was used instead of polymer (P2). The membrane thickness of the polymer electrolyte membrane was 48 μm.

[0210] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were carried out on the polymer electrolyte membrane of this comparative example by the same method 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 2 ·s·kPa) (at 80 °C and 60% relative humidity). In the SAXS measurement, no distinct scattering peaks were observed in either the dry or wet state. The volume swelling ratio was 167%.

[0211] <Example 7> (Synthesis of Polymer (P9)) To a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 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, 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 refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 72 hours while heating at 130 °C. Then, 0.004 g of decafluorobiphenyl was added, and polymerization was carried out for 3.5 hours while heating 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 (P9) containing a plurality of polymer units having the structure represented by formula (P2) and having a crosslinking group derived from decafluorobiphenyl that binds to three or more of the above polymer units. The yield was 81.9%. The Mn of the polymer (P9) measured in the same manner as in Comparative Example 1 was 54000, the Mw was 150000, and the Mw / Mn was 2.8.

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

[0213] (Fabrication of the electrolyte membrane) An electrolyte membrane of Example 7 (an electrolyte membrane composed of a proton-substituted polymer (P9)) was obtained by the same method as in Example 1, except that the polymer (P9) was used instead of the polymer (P2). The membrane thickness of the electrolyte membrane was 62 μm.

[0214] (Evaluation) For the polymer electrolyte membrane of this example, various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed in the same manner as in Comparative Example 1. The proton conductivity was 200 mS / cm (80 °C, relative humidity 100%), and it was confirmed 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 it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 4.0 nm and 5.0 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and wet state. The volume swelling ratio was 60%, and it was confirmed that the polymer electrolyte membrane of this example had excellent swelling resistance.

[0215] <Example 8> (Synthesis of the polymer (P10)) Into a 100 mL three-necked flask equipped with a nitrogen introduction tube, a stirrer, and a Dean-Stark tube, 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, and nitrogen substitution was carried out. Then, 30 mL of dimethyl sulfoxide (DMSO) and 30 mL of cyclohexane were added. After heating to 130 °C and refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 72 hours while heating at 130 °C. Then, after cooling to room temperature, 0.014 g of decafluorobiphenyl was added, and polymerization was carried out by heating at 130 °C for 3.5 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out from 1000 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 (P10) containing a plurality of polymer units having the structure represented by the formula (P2) and having a cross-linking group derived from decafluorobiphenyl that binds 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 71000, the Mw was 200000, and the Mw / Mn was 2.8. The fluorine content of the polymer P(10) measured by the same method as in Example 7 was 0.1 mass% or less.

[0216] (Fabrication of electrolyte membrane) An electrolyte membrane of Example 8 (an electrolyte membrane composed of a proton-substituted polymer (P10)) was obtained by the same method as in Example 1 except that the polymer (P10) was used instead of the polymer (P2). The membrane thickness of the electrolyte membrane was 56 μm.

[0217] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were carried out on the polymer electrolyte membrane of this example by the same method as in Comparative Example 1. The proton conductivity was 221 mS / cm (80 °C, relative humidity 100%), and it was confirmed 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) (at 80 °C and 60% relative humidity), and the polymer electrolyte membrane of this example is Nafion TM It was confirmed to have better gas barrier properties than Nafion NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 4.0 nm and 4.9 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example has a microphase separation structure in the dry state and wet state. The volume swelling rate was 58%, and it was confirmed that the polymer electrolyte membrane of this example has excellent swelling resistance.

[0218] <Example 9> (Synthesis of Polymer (P11)) To a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 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, 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 refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 72 hours while heating at 130 °C. Then, after cooling to room temperature, 0.004 g of decafluorobiphenyl was added, and polymerization was carried out by heating at 130 °C for 3.5 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was carried out 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 (P11) containing a plurality of polymer units having a structure represented by the formula (P2) and having a crosslinking group derived from decafluorobiphenyl that binds 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 48000, the Mw was 230000, and the Mw / Mn was 4.8. The fluorine content of the polymer P(11) measured by the same method as in Example 7 was 0.1 mass% or less.

[0219] (Fabrication of Electrolyte Membrane) A polymer electrolyte membrane (electrolyte membrane composed of proton-substituted polymer (P11)) of Example 9 was obtained by the same method as in Example 1, except that polymer (P11) was used instead of polymer (P2). The membrane thickness of the electrolyte membrane was 25 μm.

[0220] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed on the polymer electrolyte membrane of this example by the same method as in Comparative Example 1. The proton conductivity was 203 mS / cm (80 °C, relative humidity 100%), and it was confirmed 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 it was confirmed that the polymer electrolyte membrane of this example had better gas barrier properties than Nafion TM NR211. The interplanar spacing d in the dry state and wet state by SAXS measurement was 4.0 nm and 4.9 nm, respectively, and it was confirmed that the polymer electrolyte membrane of this example had a microphase separation structure in the dry state and wet state. The volume swelling ratio was 55%, and it was confirmed that the polymer electrolyte membrane of this example had excellent swelling resistance.

[0221] <Comparative Example 4> (Synthesis of Polymer (P12)) Into a 100 mL three-necked flask equipped with a nitrogen introduction tube, a stirrer, and a Dean-Stark tube, 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, 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 refluxing for dehydration for 4 hours, cyclohexane was extracted from the Dean-Stark tube. Polymerization was carried out for 72 hours while heating at 130 °C. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed with 300 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P12) having a crosslinked structure. The yield was 59.2%. The Mn of the polymer (P12) measured in the same manner as in Comparative Example 1 was 47,000, the Mw was 200,000, and the Mw / Mn was 4.3. In this synthesis example, since decafluorobiphenyl, which is a crosslinking agent, is reacted simultaneously with the hydrophilic monomer (M1) and the hydrophobic monomer (M2), the polymer (P12) has a structure in which the structural units derived from the hydrophilic monomer (M1), the structural units derived from the hydrophobic monomer (M2), and the crosslinkable groups derived from decafluorobiphenyl are randomly arranged.

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

[0223] (Evaluation) Various evaluations (proton conductivity evaluation, hydrogen gas permeability test, SAXS measurement, and volume swelling ratio measurement) were performed on the polymer electrolyte membrane of this comparative example by the same method 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) (relative humidity of 60% at 80°C). In the SAXS measurement, no distinct scattering peak was observed in either the dry or wet state. The volume swelling ratio was 81%. By comparing Example 7 and Comparative Example 4, it was confirmed that crosslinking at the polymer terminal improves the swelling suppression effect and proton conductivity due to crosslinking compared to a polymer with a random crosslinking interval.

[0224]

Table 1

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

Claims

1. having a structure represented by the following formula (1), 【Chemical 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 —, and n represents an integer of 10 to 100, * represents a bond. A plurality of A １ are identical to each other, A plurality of A ２ are identical to each other, A plurality of Ls １ may be the same as or different from each other A plurality of Ls ２ may be the same as or different from each other. [Chemical 2] [In formula (a1), IExG represents an ion-exchange group, L ３ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, and x represents an integer of 2 to 10, * represents a bond. A plurality of IExG may be the same as or different from each other, A plurality of Ls ３ may be the same as or different from each other. 【Chemical Formula 3】 [In formula (a2), Ar represents an arylene group having no ion-exchange group, L ４ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, and y represents an integer of 3 to 20, * represents a bond. A plurality of Ar may be the same as or different from each other, A plurality of Ls ４ may be the same as or different from each other. 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 reaction product of the polymer or an oxide thereof with a compound having three or more groups that react to form a crosslink, a polymer. 【Chemical 4】 [In formula (b1), A １ has the same meaning as described above, and X １ｂ and X ２ｂ each independently represents a halogen atom.] [Chemical Formula 5] [In formula (b2), A ２ has the same meaning as described 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.]

2. The aforementioned L １ 、the aforementioned L ２ 、the aforementioned L ３ and the aforementioned L ４ are each independently a single bond or -SO ２ -, the polymer according to claim 1.

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

4. The polymer according to claim 1 or 2, wherein the structural unit represented by the formula (a2) contains at least one selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group as the arylene group.

5. The polymer according to claim 1 or 2, having a number average molecular weight of 20,000 to 300,000.

6. The polymer according to claim 1 or 2, wherein the ratio of the weight average molecular weight to the number average molecular weight is 2.0 to 20.

0.

7. An electrolyte material containing the polymer according to claim 1 or 2.

8. An electrolyte membrane containing the polymer according to claim 1 or 2.

9. An electrolyte membrane with a catalyst layer, comprising the electrolyte membrane according to claim 8 and a catalyst layer disposed on one or both surfaces of the electrolyte membrane.

10. A membrane electrode assembly, comprising the electrolyte membrane according to claim 8 and an electrode layer disposed on one or both surfaces of the electrolyte membrane.

11. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 10.

12. A polymer electrolyte water electrolysis device comprising the membrane electrode assembly according to claim 10.

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