Novel crosslinked aliphatic anion exchange membranes with pendant pentafluorophenyl groups

Abstract

To enhance the performance of anion exchange membranes (AEMs) by constructing effective ion channels, we synthesized novel aliphatic polymers with pentafluorophenyl pendent groups via superacid catalyzed polyhydroxyalkylation and quaternization by grafting multi-cation crosslinker through the Menshutkin reaction. The procedure adopted in this study for preparing the AEMs circumvented the utilization of precious metal catalysts and made it easy to control the reaction conditions. Compared with the traditional aliphatic AEMs, the AEMs prepared by the new strategy exhibited well-developed microphase-separated structures by increasing the hydrophilic/hydrophobic difference between the polymer backbones and the side chains. Moreover, the multi-cation crosslinker not only provides ion exchange groups but also constrains the swelling of the AEMs. As we expected, the well-defined ion channels were validated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The CPFBP-TQA-100 membrane shows a highest ion conductivity of 76.85 mS cm−1 and a swelling ratio of only 24.8% at 80 °C. A maximum power density of 116.7 mW cm−2 is achieved by a single cell using the CPFBP-TQA-100 membrane at a current density of 300 mA cm−2 at 80 °C. Besides, all the AEMs display excellent thermal stability and reasonable alkaline stability.