Novel Cationic Meglumine-Functionalized Anion Exchange Membranes: Featuring Continuous Ion Channels and Excellent Alkaline Stability

Abstract

The advancement of anion exchange membranes (AEMs) is currently constrained by the difficulty in simultaneously achieving high alkaline stability and ionic conductivity. In this study, a series of AEMs with a fully carbon-based backbone and side chains incorporating the novel polyhydroxy cation meglumine (MEG) were systematically synthesized. We enhanced the water uptake (WU) (QSAN-1 achieved 324% at 80 °C) of the membrane and established large-scale continuous ion channels by leveraging the hydrophilicity of −OH and the hydrogen bonding networks formed among them. Atomic force microscopy (AFM) revealed the formation of continuous ion channels within the membranes, while small-angle X-ray scattering (SAXS) demonstrated the aggregation behavior of the cation clusters within the membrane. Through the synergistic effect of these two phenomena, the ionic conductivity was markedly improved even at a relatively low ion exchange capacity (IEC) value (1.78 mmol g^–1), with QSAN-1 achieving 64.71 mS cm^–1 at 80 °C. Furthermore, the AEMs exhibited exceptional alkaline stability, maintaining a conductivity retention rate exceeding 86% after 720 h of exposure to 2 M NaOH at 80 °C. These findings collectively validate the feasibility of utilizing MEG as a novel cation for AEM preparation, offering a promising alternative for the development of AEM materials.