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

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.