Tailoring Structure–Property Relationships in π‐Conjugated Heterocyclic Poly(arylene alkylene) Anion‐Exchange Membranes for High‐Performance Water Electrolysis

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.