End-group cross-linked membranes based on highly sulfonated poly(arylene ether sulfone) with vinyl functionalized graphene oxide as a cross-linker and a filler for proton exchange membrane fuel cell application

High-performance end-group cross-linked sulfonated poly(arylene ether sulfone) (SPAES) membranes are developed using thiolate-terminated SPAES with very high degree of sulfonation (DS) such as 90 mol% (SK-SPAES90) and vinyl functionalized graphene oxide (VGO) as a cross-linker and a filler through the thiol-Michael addition reaction. Since free-standing membranes for fuel cell application could not be prepared using the water soluble and highly proton conductive SPAES with high DS of 90 mol%, cross-linked SPAES90 membranes are intentionally prepared. The cross-linked membranes are found to have good physicochemical properties with excellent proton conductivity that can be applied for the proton exchange membrane. In particular, the cross-linked SPAES90 membrane prepared using 1.0 wt% of VGO exhibits better dimensional stability than a SPAES70 membrane from the linear SPAES with DS of 70 mol% and the proton conductivities of this membrane are larger than those of Nafion 211 at 80 °C under different relative humidity conditions (40%-95%).