Mechanically robust poly[vinyl-(4-benzyl-N,N,N-trimethylammonium bromide) ketone]/polybenzimidazole blend membranes for anion conductive solid electrolytes

In this study, a novel poly[vinyl-(4-benzyl- N , N , N -trimethylammonium bromide) ketone] (QA-PVBK) homopolymer was synthesized by conventional free-radical polymerization, followed by benzyl bromination, and in-situ quaternization reaction, successively. Blend membranes were further constructed between QA-PVBK and commercially available polybenzimidazole (PBI), as novel anion exchange membrane materials. Owing to the short repeating unit of QA-PVBK, the ion-clusters for the ion transport were highly aggregated on the microscale, which significantly contributed to the excellent hydroxide conductivity of the blend membranes. The PBI was introduced as a physical reinforcement, strengthening the membranes’ robustness and suppressing excessive swelling. Membrane PBI/QA-PVBK-OH(70%), with the QA-PVBK-OH (hydroxide form) content of 70% over the entire membrane matrix, exhibited a high hydroxide conductivity of 50.8 mS cm −1 at 60 °C, and, consequently, a good peak power density of 170.6 mW cm −2 at 60 °C/100% relative humidity condition in a H 2 /O 2 single cell test. The blend membranes also demonstrated acceptable chemical stability towards the alkaline condition (1 M NaOH at 60 °C) with the residual conductivity over 59.4% after 168 h. In light of these promising results, the present study demonstrates a facile blending process for simultaneously addressing the ion conductivity and mechanical properties of anion exchange membranes.