Base Stable Pyrrolidinium Cations for Alkaline Anion Exchange Membrane Applications

The synthesis and characterization of pyrrolidinium cation based anion exchange membranes (AEMs) are reported. Pyrrolidinium cations with various N-substituents (including methyl, ethyl, butyl, octyl, isopropyl, 2-hydroxylethyl, benzyl, and cyclohexylmethyl groups) were synthesized and investigated with respect to their chemical stability in alkaline media. The influence of substitutions on alkaline stability of pyrrolidinium cations was investigated by quantitative H-1 nuclear magnetic resonance spectroscopy (NMR) and theoretical approaches. N,N-Ethylmethyl-substituted pyrrolidinium cation ([EMPy](+)) exhibited the highest alkaline stability in this study. The synthesized AEMs based on [EMPy](+) show promising alkaline stability in strongly basic solution. The study of this work should provide a feasible way for improving the alkaline stability of pyrrolidinium cation based AEMs.