End-group cross-linked polybenzimidazole blend membranes for high temperature proton exchange membrane

A cross-linked network is obtained by an end-group cross-linkable PBI (E-PBI) and 4,4′-diglycidyl (3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP). The formation of the network is proved by FT-IR and gel fraction test. Then, high temperature proton exchange membranes are constructed by incorporating the cross-linked network into poly(2,2′-(1,3-phenylene)-5,5′-bibenzimidazole) (m-PBI). The influences of the end-group cross-linked network on the properties of membranes are studied, such as, phosphonate acid doping ability, thermal stability, mechanical property, oxidative stability and proton conductivity. The E-PBI/TMBP in the membranes contributes to the improvement of acid doping ability, proton conductivity, mechanical properties and oxidative stabilities. The blend membranes with 20–90 wt% E-PBI/TMBP show higher proton conductivity than pristine PBI at 120 °C–180 °C. These results indicate that the end-group cross-linked blend membranes are promising materials as high temperature proton exchange membranes.

► Blend membranes incorporating end-group cross-linked network were obtained.
► The thermal and oxidative stabilities of the membranes were much improved.
► The cross-linked network balanced the conductivity and mechanical properties.
► The blend membranes combined the enhanced strength with better flexibility.