Developing Alkaline Exchange Membranes Using Multisegmented Block Copolymers from Friedel–Crafts Hydroxyalkylation Polycondensation

Abstract

Microphase separation is a successful method for forming polymer membranes with simultaneous high ionic conductivity and dimensional stability. In this study, we developed a new strategy for designing anion exchange membranes (AEMs) with inherent microphase separation and improved alkaline stability via Friedel−Crafts (F−C) hydroxyalkylation polycondensation. We achieved stable microphase separation in the membrane when multisegmented block copolymers (MSBCPs) synthesized from the F−C hydroxyalkylation reaction were used for casting films. The formation of MSBCPs and microphase separation were confirmed by proton nuclear magnetic resonance spectroscopy and small-angle X-ray scattering spectroscopy, respectively. In comparison to F−C random copolymers, the F−C MSBCPs with the same ion-exchange capacity showed higher hydroxide conductivity (67 mS/cm at 80 °C) with lower water uptake and swelling degree. This membrane retained 52% of the fresh ionic conductivity and maintained microphase segregation after being soaked in a 1 M KOH aqueous solution at 80 °C for 28 days. This synthetic method offers a new pathway for producing AEMs with structure control and stable ion channels.