Plasma graft-polymerization for synthesis of highly stable hydroxide exchange membrane

A novel plasma graft-polymerization approach is adopted to prepare hydroxide exchange membranes (HEMs) using cardo polyetherketone powders (PEK-C) and vinylbenzyl chloride. The benzylic chloromethyl groups can be successfully introduced into the PEK-C polymer matrix via plasma graft-polymerization. This approach enables a well preservation in the structure of functional groups and formation of a highly cross-linked structure in the membrane, leading to an improvement on the stability and performance of HEMs. The chemical stabilities, including alkaline and oxidative stability, are evaluated under severe conditions by measuring hydroxide conductivity and weight changes during aging. The obtained PGP-NOH membrane retains 86% of the initial hydroxide conductivity in 6 mol L-1 KOH solution at 60 degrees C for 120 h, and 94% of the initial weight in 3 wt% H2O2 solution at 60 degrees C for 262 h. The PGP-NOH membrane also possesses excellent thermal stability (safely used below 120 degrees C), alcohol resistance (ethanol permeability of 6.6 x 10(-11) m(2) s(-1) and diffusion coefficient of 3.7 x 10(-13) m(2) s(-1)), and an acceptable hydroxide conductivity (8.3 mS cm(-1) at 20 degrees C in deionized water), suggesting a good candidate of PGP-NOH membrane for HEMFC applications. (C) 2013 Elsevier B.V. All rights reserved.