| abstract |
The copolymer includes divalent units represented by formula —[CF 2 —CF 2 ]—, divalent units represented by formula: and one or more divalent units independently represented by formula: The copolymer has an —SO 2 X equivalent weight in a range from 300 to 2000. A polymer electrolyte membrane that includes the copolymer and a membrane electrode assembly that includes such a polymer electrolyte membrane are also provided. |