(680c) Polyethylene-Based Block Copolymer Alkaline Anion Exchange Membranes: Synthesis, Preparation, and Characterization

We synthesized and characterized polyethylene-based block copolymer alkaline anion exchange membranes (AAEM) derived from polyethylene-block-polystyrene-block-polyethylene (ESE) triblock copolymer. The ESE triblock precursor polymer was prepared by anionic polymerization of 1,4-polybutadiene-block-polystyrene-block-1,4-polybutadiene followed by selective hydrogenation of the polybutadiene blocks, and the polystyrene block of the ESE precursor polymer was functionalized with boromalkyl groups by acid-catalyzed Friedel-Crafts alkylation reactions. The bromoalkyl-functionalized ESE triblock copolymers were film-casted at an elevated temperature, and the bromo groups in the solid ESE films were quaternized using trimethylamine. Three ESE AAEMs with ion exchange capacities (IECs) from 0.76 to 2.05 mequiv./g with hydroxide counter ions were prepared and characterized. The conductivity of the ESE AAEMs increases with the IEC, and the maximum conductivity of hydroxide 55 mS/cm was achieved. The microstructures of ESE AAEMs were characterized using synchrotron SAXS technique, and anisotropy in the microstructure of block copolymers largely originated from the film-casting process was observed.