A novel strategy to construct polybenzimidazole linked crosslinking networks for polymer electrolyte fuel cell applications

A novel strategy to construct polybenzimidazole linked crosslinking networks (PLCNs) is proposed. A benzoxazine-ended PBI oligomer (BPBI) is prepared, which can react with PBI from the ended benzoxazine groups to form PLCNs. It is proved that the ring-opening reaction of benzoxazine is activated by benzimidazoles mainly from the N-H site in a BIm-rich background and forms phenoxy-type, phenolic-type and crosslinking structures successively under heat. Crosslinked by 15 wt% of BPBI, properties of PBI are remarkably improved with 74% enhancement on tensile strength, 78 degrees C improvement on sub-T g transition temperature and 49% increasement on acid uptake. Besides, PBI-Ben(15)-356%PA exhibits a high proton conductivity of 0.122 S cm(-1) with a low activation energy of 17.2 kJ mol(-1) under 180 degrees C. As BPBI is thermally stable at room temperature and can crosslink commercial PBI simply by heat, it exhibits promising commercial prospects in the application of polymer electrolyte fuel cells.