| abstract |
A polymer electrolyte membrane is provided having a thickness of 90 microns or less and comprising a polymer, said polymer comprising a highly fluorinated backbone and recurring pendant groups according to the formula: YOSO2-CF2-CF2-CF2-CF2-O-[polymer backbone] (I) where Y is H+ or a monovalent cation such as an alkali metal cation. Typically, the membrane is a cast membrane. Typically, the polymer has a hydration product of greater than 22,000. Typically, the polymer has an equivalent weight of 800-1200. |