Synthesis of highly fluorinated poly(arylene ether)s copolymers for proton exchange membrane materials

Highly fluorinated poly(arylene ether)s containing sulfonic acid groups meta to ether linkage (SPAE), intended for fuel cell applications as proton electrolyte membrane materials, were synthesized by potassium carbonate mediated nucleophilic polycondensation reactions of commercially available monomers: 2,8-dihydroxynaphthalene-6-sulfonated salt (2,8-DHNS-6), hexafluorobisphenol A (6F-BPA), and decafluorobiphenyl (DFBP) in dimethylsulfoxide (DMSO) at 160–170 °C. FT-IR and 1H NMR were used to characterize the structures. The sulfonate or sulfonic acid contents (SC), expressed as a number per repeat unit of polymer and ranged from 0 to 0.79, were calculated from 19F NMR. The proton conductivities of acid form membrane increased with SC value and reached 0.103 S/cm at 90 °C for SPAE 80. The methanol permeabilities ranged from 7.4 × 10−7 to 2.2 × 10−9 cm/s at 30 °C and were lower than those of other conventional sulfonated ionomer membranes, particularly commercial perfluorinated sulfonated ionomer (Nafion).