Enhancing side chain swing ability by novel all-carbon twisted backbone for high performance anion exchange membrane at relatively low IEC level

Abstract

A novel all-carbon backbone-based membrane is designed by introducing side chains at the non-coplanar site of twisted “ether-free” main chain via Suzuki coupling reaction. The twisted backbone reduces the hindrance effect, providing broader mobile space for the side chains and enhancing the swing ability of the side chains to facilitate the formation of ion channels and the transportation of OH⁻. As a result, the high conductivity is obtained at a relatively low IEC level. The QPS-PB-4 membrane exhibits a superior OH⁻ conductivity of 50.1 to 94.4 mS cm⁻¹ at 30 ℃ to 80 ℃ with an IEC of only 1.48 mmol g⁻¹, and a low swelling ratio of less than 10%. Which show significant advantage among the traditional side-chain-type AEMs reported in recent years. Moreover, the as-prepared membranes have good mechanical and thermal stability, as well as excellent chemical stability because of the all-carbon backbone designed without any sensitive sites that can be attacked by hydroxide. The conductivity of the QPS-PB-4 membrane decrease by only 8% after treatment at 80 ℃ in 1 M NaOH for 1800 h. The fuel cell assembled with the as-prepared membrane has a peak power density of up to 558.8 mW cm⁻², indicating the promising application potential of the membranes.