(588a) Chemical Stability and Ion Transport in Polymerized Ionic Liquid Block Copolymer Anion Exchange Membranes with Various Cations

Authors: 
Elabd, Y. A., Texas A&M University
Meek, K. M., Drexel University
Beyer, F. L., US Army Research Laboratory

New highly hydroxide-conductive anion exchange membranes (AEMs) with high alkaline chemical stability are required in order to achieve long-lasting low-cost solid-state alkaline fuel cells (AFCs). In this study, we synthesized and investigated the chemical stability of methacrylate-based polymerized ionic liquids (PILs) consisting of various covalently attached cations: butylimidazolium, butylmethylimidazolium, trimethylammonium, pentamethylguanidinium, butylpyrrolidinium, trimethylphosphonium. The degradation pathways and extent of chemical stability of the PILs were determined using 1H NMR spectroscopy after exposure to various pHs, temperatures, and times. Additionally, corresponding diblock copolymers consisting of a non-ionic component, methyl methacrylate (MMA), and a functional component, 2-bromoethyl methacrylate (BrEMA), were synthesized via the sequential reversible addition-fragmentation chain-transfer (RAFT) polymerization technique and subsequently functionalized with the same six cations to form a series of PIL block copolymers with the same composition and molecular weight. Ion transport, water content, and morphology were measured in each PIL block copolymer using electrochemical impedance spectroscopy, dynamic vapor sorption, small-angle X-ray scattering, and transmission electron microscopy. PIL block copolymer transport-morphology relationships at various humidities and temperatures with regard to cation type will be presented.