Tailoring Structure-Property Relationships in π-Conjugated Heterocyclic Poly(arylene alkylene) Anion-Exchange...

Anion-exchange membrane water electrolysis (AEMWE) is a promising technology for sustainable hydrogen production, but practical applications are limited by the trade-off between hydroxide conductivity and alkaline stability of anion-exchange membranes (AEMs). Here, we report a molecular design strategy that regulates ion transport pathways and membrane stability by tethering quaternary ammonium cations via flexible side chains to π-conjugated heterocyclic backbone polymers. Durable cationic copolymers containing p-terphenyl with dibenzofuran (DBF) or dibenzothiophene (DBT) units are synthesized. Combined experimental and theoretical studies establish structure-property relationships linking heteroatom chemistry to the hydration, microphase morphology, and ion transport. DBF-units promote dense hydrogen bonding networks, whereas DBT-units strengthen ion-dipole interactions and induce more pronounced microphase separation. Consequently, optimized DBF- and DBT-based membranes exhibit hydroxide conductivities exceeding 180 and 200 mS cm^-1, respectively, at 80°C. In AEMWEs using non-precious-metal catalysts, these membranes deliver current densities above 4.1 and 5.1 A cm^-2 at 2 V, respectively. The DBT-based membrane also maintains stable operation for over 1600 h at 1 A cm^-2 and 60°C. This work establishes structure-performance relationships and provides a practical molecular design strategy for highly conductive, durable AEMs based on π-conjugated heterocyclic backbone units.