Positional Engineering of Ionic Side Chains Enhances π-π Stacking in Poly(m-Terphenylene Alkylene) Anion Exchange Membranes to Address the Conductivity-Stability Tradeoff

As critical components of anion exchange membrane fuel cells (AEMFCs) and water electrolyzers (AEMWEs), anion exchange membranes (AEMs) still face significant challenges associated with inadequate alkaline stability and ionic conductivity. In this study, the positional engineering of ionic side chains in poly(m-terphenylene alkylene) addresses the long-standing challenge of balancing conductivity and stability in conventional AEMs. By relocating quaternary ammonium groups from aliphatic segments to rigid aromatic terphenyl units (P1-NTP), enhanced π-π stacking promotes the efficient self-assembly of ionic clusters and well-connected nanochannels. This molecular design simultaneously delivers enhanced hydroxide conductivity (155 mS cm^–1 at 80 °C, > 35% higher than conventional analogs), reduced swelling (12% vs 24% in controls), and excellent chemical stability─retaining > 93% weight after 24 h in Fenton’s reagent and > 91% conductivity after 8000 h in 1 M NaOH at 80 °C. The resolved tradeoff enables superior device performance, with AEMFC achieving 670 mW cm^–2 peak power density and AEMWE reaching 4.00 A cm^–2 at 1.88 V with > 100 h operational stability. This work presents a feasible approach to develop durable and high-performance AEMs and provides meaningful insights into the structure–property relationship.