Photocrosslinking of sulfonated poly(arylene ether sulfone) in a swollen state

Novel photocrosslinkable sulfonated poly(arylene ether sulfone)s containing chalcone moieties in the polymer backbone (SPAEF) were synthesized from 4,4'-dihydroxychalcone (4DHC), 4,4'-difluorodiphenylsulfone-3,3'-disulfonate (SDFDPS) and decafluorobiphenyl (DFBP). We introduced a new strategy to crosslink photosensitive polymer electrolyte membranes by UV irradiation in a swollen state in order to preserve the interconnected hydrophilic channels in the hydrated SPAEF electrolyte membrane. Photocrosslinked membranes showed desired effects of improved mechanical properties with significantly low methanol diffusion coefficient, while maintaining high proton conductivity. SPAEF membranes after the photocrosslinking exhibited a proton/methanol selectivity of 7.6 x 10(5) S s cm(-3) at 30 degrees C, which is 21 times higher than that of Nafion (R) 117. This novel photocrosslinking strategy also improved oxidative and hydrolytic stabilities of polymer membranes which are desirable for direct methanol fuel cell application.