Solid polymer electrolyte material, liquid composition, solid polymer fuel cell and fluoropolymer

1. A solid polymer fuel cell comprising an anode, a cathode and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the cathode contains, as a constituting material, a solid polymer electrolyte material made of a copolymer comprising a repeating unit based on a fluoromonomer A which gives a polymer having an alicyclic structure in its main chain by radical polymerization, and a repeating unit based on a fluoromonomer B′ of the following formula (1″):

CF 2 ═CF(R f ) j SO 3 H  (1″)

wherein j is 0 or 1, and R f is a C 1-20 polyfluoroalkylene group having a straight chain or branched structure which may contain ether oxygen atoms.

2. The solid polymer fuel cell according to claim 1 , wherein the fluoromonomer B′ is represented by the following formula (2″), and the repeating unit based on the fluoropolymer A is represented by the following formula (3):

CF 2 ═CFO(CF 2 CFYO) k (CF 2 ) m SO 3 H  (2″)

wherein k is an integer of from 0 to 2, m is an integer of from 1 to 12, and Y is a fluorine atom or a trifluoromethyl group;

wherein each of p, q and r which is independent of one another, is 0 or 1, each of R f1 and R f2 which may be the same or different, is a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group, and R f3 is a C 1-3 perfluoroalkylene group which may contain a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group, as a substituent.

3. The solid polymer fuel cell according to claim 1 , wherein the fluoromonomer A is perfluoro(3-butenyl vinyl ether), and the fluoromonomer B′ is represented by the following formula (6″):

CF 2 ═CFO(CF 2 CFYO) k .(CF 2 ) 2 SO 3 H  (6″)

wherein k′ is 0 or 1, and Y is a fluorine atom or a trifluoromethyl group.

4. The solid polymer fuel cell according to claim 1 , wherein the fluoromonomer B′ is represented by the following formula (2″), and the repeating unit based on the fluoropolymer A is represented by the following formula (4):

CF 2 ═CFO(CF 2 CFYO) k (CF 2 ) m SO 3 H  (2″)

wherein k is an integer of from 0 to 2, m is an integer of from 1 to 12, and Y is a fluorine atom or a trifluoromethyl group;

wherein s is 0 or 1, each of R f4 , R f5 , R f6 and R f7 which may be the same or different, is a fluorine atom or a C 1-5 perfluoroalkyl group (provided that R f4 and R f5 may be connected to form a spiro ring when s is 0), and R f8 is a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group.

5. The solid polymer fuel cell according to claim 4 , wherein the fluoromonomer A is at least one member selected from the group consisting of perfluoro(2,2-dimethyl-1,3-dioxole), perfluoro(1,3-dioxole) and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, and the fluoromonomer B′ is represented by the following formula (6″):

CF 2 ═CFO(CF 2 CFYO) k .(CF 2 ) 2 SO 3 H  (6″)

wherein k′ is 0 or 1, and Y is a fluorine atom or a trifluoromethyl group.

6. The solid polymer fuel cell according to claim 5 , wherein the fluoromonomer A is perfluoro(2,2-dimethyl-1,3-dioxole).

7. The solid polymer fuel cell according to claim 5 , wherein the fluoromonomer A is perfluoro(1,3-dioxole).

8. The solid polymer fuel cell according to claim 5 , wherein the fluoromonomer A is 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole.

9. The solid polymer fuel cell according to claim 1 , wherein the fluoromonomer B′ is represented by the following formula (2″), and the repeating unit based on the fluoropolymer A is represented by the following formula (5):

CF 2 ═CFO(CF 2 CFYO) k (CF 2 ) m SO 3 H  (2″)

wherein k is an integer of from 0 to 2, m is an integer of from 1 to 12, and Y is a fluorine atom or a trifluoromethyl group;

wherein each of R f9 , R f10 , R f11 and R f12 which may be the same or different, is a fluorine atom or a C 1-5 perfluoroalkyl group.

10. The solid polymer fuel cell according to claim 9 , wherein the fluoromonomer A is perfluoro(2-methylene-4-methyl-1,3-dioxolane), and the fluoromonomer B′ is represented by the following formula (6″):

CF 2 ═CFO(CF 2 CFYO) k .(CF 2 ) 2 SO 3 H  (6″)

wherein k′ is 0 or 1, and Y is a fluorine atom or a trifluoromethyl group.

11. The solid polymer fuel cell according to any of claim 1 - 3 or claims 4 - 10 , wherein solid polymer electrolyte material has an ion exchange capacity of from 0.9 to 1.5 meq/g dry resin.