Proton-conductive polymeric ionic liquids block copolymer of poly(vinylphosphonic acid)/1-propylimidazole-b-polystyrene for polymer electrolyte membrane fuel cells

Abstract

Polymer electrolyte membrane (PEM) fuel cells have challenges in operation under low-humidity conditions caused by a proton conduction mechanism dependent on water. We focused on polymeric ionic liquids (PILs), which are promising for high proton conductivity under a wide range of environments because they have the characteristics of polymer electrolyte liquids. However, it is difficult to fabricate self-standing membranes of PILs due to their high hygroscopicity and fluidity. In this paper, to inhibit the fluidity of the PIL in developing a self-standing PEM, the hydrophobic chain segment of styrene is inserted between the PILs of poly(vinylphosphonic acid/1-propylimidazole) (P(VPA/1PIm)) by RAFT polymerization. The synthesized sample of P(VPA/1PIm)-block-polystyrene is potentially applicable to PEM materials because it was obtained in powder state, having a high heat resistance of up to 300 °C, and exhibiting a proton-conducting property under a wide range of environments.