Synergistic backbone-side chain design via noncovalent interactions for advanced high-temperature proton exchange membranes.

High-temperature proton exchange membrane (HT-PEM) fuel cells are essential for efficient hydrogen energy conversion, yet their performance is often limited by insufficient proton transport and poor phosphoric acid (PA) retention of HT-PEMs. Current strategies mainly rely on covalent structural modification, with limited focus on intermolecular interactions. Here, we propose a molecular design that regulates non-covalent interactions to simultaneously enhance conductivity, chemical stability, and PA retention. Poly(arylene alkylene) membranes were synthesized by incorporating dibenzo-18-crown-6 units into an aromatic backbone and flexible alkyl side chains bearing quaternary ammonium or imidazolium groups. The crown ether units introduce dipole interactions and additional PA binding sites, while the flexible side chains enable dynamic coupling with the backbone. Methyl-substituted imidazolium groups further strengthen PA binding through improved charge delocalization. This synergistic design promotes well-defined microphase separation and forms a stable proton transport network. The optimized membrane (PTC0.3H-DMI) exhibits a proton conductivity of 65.3 mS cm-1 at 180 °C and a peak power density of 1152 mW cm-2 under anhydrous conditions. It also maintained stable voltage output during long-term operation under 200 and 400 mA cm-2 at 160 °C. This work highlights the importance of non-covalent interactions (especially dipole coupling and hydrogen bonding) and provides a practical strategy for designing advanced HT-PEMs.