Multiply quaternized poly(phenylene oxide)s bearing β-cyclodextrin pendants as “assisting moiety” for high-performance anion exchange membranes

Abstract

A bulky and hydrophilic β-cyclodextrin group, serving as a “performance assisting moiety”, was grafted onto a poly(phenylene oxide) (PPO) to achieve a new family of polymer electrolytes with different kinds of quaternary ammonium salts (QAs) for anion exchange membranes (AEMs). It was observed that the β-cyclodextrin involved AEMs having a well-designed molecular architecture exhibited some attractive properties. At the same ion exchange capacity level, the highest conductivity at 80 °C of the cyclodextrin-involved anion exchange membranes reached 110.8 mS cm−1, which was almost twice as high as that of a reference membrane. As a novel “assisting moiety”, the incorporation of the functional cyclodextrin groups also endowed membranes with suitable water uptakes of 60.2–93.8% and swelling ratios of 11.5–22.8% at 80 °C. A comparative study revealed that the cyclodextrin-involved membranes had an improved alkaline stability and a satisfactory cell performance. The maximum power density of one cyclodextrin-based membrane was 154 mW cm−2, which was three folds higher than that of the analogue without “assisting moiety”. In general, this study offers an effective synthetic strategy to prepare the high-performance anion exchange membranes with an excellent combination of high conductivity, low swelling, good alkaline stability and reasonable cell performance.