Anion Exchange Membranes Based on Poly(aryl piperidinium) Containing Both Hydrophilic and Hydrophobic Side Chains

Recently, ether-free poly(aryl piperidinium) polymers have been considered as promising materials for developing anion exchange membranes (AEMs), because of their excellent alkaline stability and facile synthesis methods. However, its main chain structure hinders the formation of wide ion-transport networks, limiting the further improvement of its performance. Herein, we introduce both hydrophilic and hydrophobic side chains into the poly(aryl piperidinium) backbone to promote the aggregation of ionic clusters and the formation of microphase-separated structures. The AEMs are designed by introducing 1-(6-bromohexyl)-N-methyl piperidinium bromide (hydrophilic) and 1-bromohexane (hydrophobic) into the poly(m-terphenyl piperidinium) backbone. After grafting hydrophilic and hydrophobic side chains, the resulted membrane (m-PTP–32P8C) exhibits outstanding conductivity (112 mS cm–1 at 80 °C) and dimensional stability. Meanwhile, under the alkaline condition of 1 mol L–1 NaOH at 80 °C, the conductivity is still maintained above 80% after 1200 h of immersion. When used in the water electrolysis cell with a nonplatinum group metal anode, the m-PTP–32P8C membrane presents a high current density of 0.752 A cm–2 at 2.2 V with the electrolyte of 1 mol L–1 KOH at 60 °C. Compared with those grafted with only hydrophilic or hydrophobic side chains, m-PTP–32P8C exhibits better physicochemical properties and conductivity.