Rigid–Flexible Polybenzimidazole-Based Polymers Integrated with Poly(vinylidene fluoride) as Matrix Membranes for Enhanced High-Temperature Proton Conduction

Polybenzimidazoles (PBIs) possess the specific merits of high thermal and chemical stability and plentiful binding sites for acidic proton carriers, thereby showing promising applications in high-temperature proton conduction. However, the fully rigid construction leads to a compact structure of PBIs, which restricts the adsorption and retention of proton carriers, resulting in limited proton conductivity and poor mechanical properties. Herein, we show that the polybenzimidazole-based polymers of intrinsic microporosity (PIM–PBIs), which integrate flexible and rigid structures by introducing an aromatic ether bridge, could significantly increase the proton conductivity. The resulting PIM–PBIs possessing better solubility enabled the excellent compatibility of poly(vinylidene fluoride) (PVDF), thereby achieving a high acid doping level and building an abundant hydrogen bond network. As a result, the PIM–PBIs/PVDF membrane could achieve a high proton conductivity (208.5 mS cm^–1at 140 °C), excellent PA retention ability (98%), and high mechanical property (21.7 MPa). This work may provide a guideline for the design of proton-conducting materials with high proton conductivities.