Multi-cation side-chain-type containing piperidinium group poly(2,6-dimethyl-1,4-phenylene oxide) alkaline anion exchange membranes

A series of alkaline anion exchange membranes (AAEMs) based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with multi-cation side chain containing piperidinium group were fabricated via nucleophilic substitution and Menshutkin reaction. The chemical structures of the AAEMs (PPO-AMP-X) were determined by Fourier transform infrared and proton nuclear magnetic resonance spectra. The resultant PPO-AMP-X membranes with the ion exchange capacities (IECs) of 2.05–2.77 mmol g −1 displayed the hydroxide conductivities in the range of 61.04–78.92 mS cm −1 at 80°C. When tested at the same degree of functionalization levels, the PPO-AMP-X membranes exhibited significantly higher hydroxide conductivity and lower conductivity loss than conventional AAEMs bearing benzyltri-methylammonium group (PPO-TMA). The PPO-AMP-28 multi-cation membrane showed a hydroxide conductivity of 70.52 mS cm −1 at 80°C, which was nearly two times higher than that of the PPO-TMA-28 single-cation membrane (36.74 mS cm −1 ). Compared with PPO-TMA-28 (56.76% decrease), the hydroxide conductivity of PPO-AMP-28 merely decreased by 23.15% after soaked in 1 M KOH at 80°C for 500 h. Additionally, the PPO-AMP-X membranes displayed moderate mechanical properties and good thermal stabilities, which can meet the basic requirements for use in fuel cells. This study provides a facile method for preparing AAEMs with multi-cation side chain containing piperidinium group.