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

• Published in: Polymer (Guilford) 2020-06, Vol.201, p.122555, Article 122555
• Main Authors: Duan, Chongxiong, Luo, Haochuan, Li, Jingling, Liu, Cuiyin
• Format: Article
• Language: English
• Subjects: Benzimidazoles; Benzoxazine; Benzoxazines; Crosslink; Crosslinking; Electrolytes; Electrolytic cells; Fuel cells; Fuel technology; Phenolic compounds; Phenols; Polybenzimidazole; Polybenzimidazoles; Polymers; Proton exchange membrane fuel cells; Ring opening; Room temperature; Tensile strength; Thermal stability; Transition temperature; Transition temperatures
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2020.122555

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. Polybenzimidazole linked crosslinking networks were constructed and displayed excellent mechanical strength, good thermal stability and high acid uptake. [Display omitted] •Novel polybenzimidazole linked crosslinking networks were constructed.•Benzoxazine was confirmed to react with benzimidazole mainly from the N-H site of benzimidazole.•Great improvements on mechanical strength, acid uptake and glass transition temperature were realized by crosslinking.•High proton conductivity of 0.122 S cm−1 under 180 °C was achieved.