Proton exchange membranes for fuel cell applications
View Patent ↗A proton conductive graft polymer comprises at least a structure unit of a sulfonated polymer side chain covalently attached to a hydrophobic perfluorocyclobutane polymer main chain. The sulfonated condensation polymer side chain has a high local ion exchange capacity while the main polymer chain is substantially free of sulfonic acid group. A membrane made from the graft polymer can provide good mechanical properties and high proton conductivity at wide range of humidity and temperatures.
1. A polymer that is useful for fuel cell applications, the polymer comprising segments 1 and 2:
wherein:
Z 1 is —SO 2 X, —PO 3 H 2 , or —COX;
E 1 , E 2 are each independently an aromatic-containing and/or aliphatic-containing moiety;
X is an —OH, a halogen, an ester, or
d is the number of Z 1 attached to E 1 ;
P 1 , P 2 , P 3 , P 4 are each independently: absent, —O—, —S—, —SO—, —CO—, —SO 2 —, —NH—, NR 2 —, or —R 3 —, and
R 2 is C 1-25 alkyl, C 1-25 aryl or C 1-25 arylene;
R 3 is C 1-25 alkylene, C 1-25 perfluoroalkylene, perfluoroalkyl ether, alkylether, or C 1-25 arylene;
R 4 is trifluoromethyl, C 1-25 alkyl, C 1-25 perfluoroalkylene, C 1-25 aryl, or another E 1 group;
R 8 (Z 1 ) d is a moiety having d number of protogenic groups; and
Q 1 , Q 2 are each independently a fluorinated cyclobutyl moiety.
2. The polymer of claim 1 wherein the polymer comprises a polymer having polymer units 3 and 4:
i is a number representing repetition of polymer segment 1 to define a polymer unit 3; and
j is a number representing repetition of polymer segment II to define polymer unit 4.
3. The polymer of claim 2 wherein i and j are each independently an integer from 1 to 400.
4. The polymer of claim 1 wherein d is equal to the number of aromatic rings in E 1 .
5. The polymer of claim 1 wherein d is an integer from 1 to 4.
6. The polymer of claim 1 wherein Q 1 and Q 2 are each independently a perfluorocyclobutyl moiety.
7. The polymer of claim 1 wherein Q 1 and Q 2 are each independently:
8. The polymer of claim 1 wherein E1 and E2 are each independently selected from the group consisting of:
9. The polymer of claim 1 having the following formula:
10. The polymer of claim 1 wherein R 8 comprises a chemical structural unit selected from the group consisting of:
—(CF 2 ) m SO 2 X 4 , —SO 2 X 4 , —(CH 2 ) m SO 2 X 4 ,
and
wherein m is a positive integer and X 4 is —OH or a halogen atom.
11. The polymer of claim 1 wherein R 8 comprises a chemical structural unit selected from the group consisting of:
wherein n is an integer.
12. A polymer membrane electrode comprising the polymer of claim 1 .