Fluorinated poly(arylenethioethersulfone) copolymers containing pendant sulfonic acid groups for proton exchange membrane materials

Fluorinated sulfo-pendants poly(arylenethioethersulfone) copolymer, which contained 50 mol% sulfonate content per repeat unit (6F-SPTES-50), were synthesized by a nucleophilic polycondensation from 4,4-(hexafluoroisopropylidene)-diphenylthiol, 3,3′-disulfonate-4,4′-difluorodiphenylsulfone and 4,4′-difluorodiphenylsulfone. The 6F-SPTES-50 copolymer possessed high molecular weight, exhibited good film formability and thermal stability, and maintained adequate mechanical strength after immersion in water for 24 h. The proton conductivities of the 6F-SPTES-50 copolymer membrane increased with temperatures, reaching values above 120 mS/cm at 85 °C and 85% relative humidity. Preliminary MEA test shows acceptable performance, which indicated that these materials are promising proton exchange membranes (PEMs) for fuel cells operated at medium temperatures.