Hydrophobic side chains to enhance hydroxide conductivity and physicochemical stabilities of side-chain-type polymer AEMs

Anion exchange membranes (AEMs) of side-chain polymers have attracted growing attention recently in the fuel cells. However, their dimensional stability and alkali resistance still not meet the requirements for industrial application of fuel cells. Herein we demonstrate a facile approach to prepare the side-chain-type polymer AEMs with high performances via introducing both hydrophobic and hydrophilic side chains onto the backbone. Grafting hydrophobic side chain into the backbone favor to construct a well-defined micro-phase separation structure and fabricate fast ion transporting pathway. The resulting polyethersulfone (PES) based AEMs display a high hydroxide conductivity and good physicochemical stability. Impressively, the PES-8C0.15-QA0.85 AEM has a 54.3% increase in the hydroxide conductivity and a 45% decrease in the swelling ratio (SR) by introducing a small amount of hydrophobic side chain. Furthermore, the AEMs show good mechanical properties, alkaline tolerance and oxidative stability. The loss of ionic exchange capacity and hydroxide conductivity is less than 15% after alkaline treatment (1 M KOH, 60 °C, 480 h). This approach will be favorable to exploit practical AEMs for fuel cells.