Sterically engineered bulky crosslinked poly(arylpiperidinium) anion exchange membranes with microphase-separated morphology and superior dimensional stability

High-performance anion exchange membranes (AEMs) are essential for anion exchange membrane fuel cells, but balancing ionic conductivity and dimensional stability remains challenging. Herein, a locally dense cationic polyarylpiperidine AEMs was successfully developed by conducting a one-pot cross-linking reaction with Br-hexamethylphenyl benzene which has dense cross-linking sites and a large volume, as both a cross-linking agent and a quaternizing reagent, and polytriphenylpiperidine. The resulting crosslinked network suppressed polymer chain motion and swelling, while promoting microphase separation for efficient ion transport. The optimized membrane, QHCTP-10, showed a low swelling ratio (11.81 %) and high hydroxide conductivity (128.74 mS cm −1 ) at 80 °C, with excellent mechanical strength (Ts = 34.67 MPa, Eb = 8.52 %) and remarkable alkaline stability, retaining 95.13 % conductivity after 1200 h in 1 M NaOH at 80 °C. Fuel cell tests demonstrated a peak power density of 581.87 mW cm −2 at 1633.67 mA cm −2 and stable operation for 70 h at 0.10 A cm −2 almost without voltage decay under H 2 /O 2 conditions. This work demonstrates that introducing bulky crosslinkers with dense reactive sites offers a promising strategy to develop AEMs with high conductivity, stability, and fuel cell performance.