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

Abstract 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 °C improvement on sub-Tg 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 °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.