Pyrrolidinium‐Based Hyperbranched Anion Exchange Membranes with Controllable Microphase Separated Morphology for Alkaline Fuel Cells

It is well acknowledged that the microphase-separated morphology of anion exchange membranes (AEMs) is of vital importance for membrane properties utilized in alkaline fuel cells. Herein, a rigid macromolecule poly(methyldiallylamine) (PMDA) is incorporated to regulate the microphase morphology of hyperbranched AEMs. As expected, the hyperbranched poly(vinylbenzyl chloride) (HB-PVBC) is guided to distribute along PMDA chains, and longer PMDA cha leads to a more distinct microphase morphology with interconnected ionic channels. Consequently, high chloride conductivity of 10.49 mS cm−1 at 30 °C and suppressed water swelling ratio lower than 30% at 80 °C are obtained. Furthermore, the β-H of pyrrolidinium cations in the non-antiperiplanar position increases the energy barrier of β-H elimination, leading to conformationally disfavored Hofmann elimination and increased alkaline stability. This strategy is anticipated to provide a feasible way for preparing hyperbranched AEMs with clear microphase morphology and good overall properties for alkaline fuel cells.