Amphiphilic Block Copolymer Containing Quaternary Ammonium Cation for Anion Exchange Membrane

Abstract

Amphiphilic block copolymers are excellent materials for potential alkaline anion exchange membrane (AAEM) application. In this study, a new synthetic pathway was investigated for copolymerization of polybutadiene-b-poly(vinylbenzyl trimethyl ammonium chloride) (PB-b-P[VBTMA][Cl]). This amphiphilic diblock copolymer synthesis first involved formation of benzyloxyamine functionalized polybutadiene by using 2,2,6,6-tetramethyl-1-(2-bromo-1-phenylethoxy) piperidine to terminate living anionic polymerization of butadiene in cyclohexane at room temperature, and then the nitroxide-functionalized polybutadiene acted as a macroinitiator to polymerize vinylbenzyl chloride (VBC) by nitroxide mediate polymerization at 125°C in the bulk. Polybutadiene-b-pol(vinylbenzyl chloride) (PB-b-PVBC) was sequentially quaternized by trimethylamine gas in chloroform. Gel permeation chromatography (GPC) clearly showed the increase in molecular weight of PB-b-PVBC diblock copolymer, and the PB-b-PVBC was also characterized by the 1H NMR spectroscopy. Infrared spectroscopy confirmed the formation of quaternary ammonium cation. Finally, PB-b-P[VBTMA][Cl] was solvent cast in a chloroform/methanol co-solvent mixture, this solvent processability extend utility of PB-b-P[VBTMA][Cl] in AAEM application.