Aryl‐Ether‐Free Polyaromatics‐Based Alkaline‐Resistant Anion exchange PTFE Composite Membrane

Novel aryl‐ether‐free polyaromatics with different‐sized cationic headgroups tethered to the backbone are synthesized via superacid‐catalyzed polycondensations and subsequent Menshutkin quaternization reactions for potential application as anion exchange membranes (AEMs) in electrolysis. Experimentally, the effect of four different heterocycloaliphatic quaternary ammonium cationic headgroups on the AEM properties, such as the hydroxide conductivity, water uptake, swelling ratios and alkaline stability, is fully explored. Thin films are prepared by spin‐coating these AEMs onto porous polytetrafluoroethylene substrates. With a high degree of quaternization, these new aryl‐ether free polyaromatic thin film AEMs achieved high conductivities and good mechanical stability. The highest hydroxide conductivity of 45 mS cm−1 is achieved with excellent alkaline stability and conductivity retention of 96% after 30 days in 1 m KOH at 80 °C. Due to the polytetrafluoroethylene substrates, the swelling ratios and water uptake are relatively small, which ensured the astute dimensional stability of these thin film AEMs. The combined effect of alkaline‐stable cationic headgroups, an aromatic backbone and a robust substrate led to a promising thin‐film AEM.