Understanding Anion Transport in an Aminated Trimethyl Polyphenylene with High Anionic Conductivity

An alkaline exchange membrane (AEM) based on an aminated trimethyl poly(phenylene) is studied in detail. This article reports hydroxide ion conductivity through an in situ method that allows for a more accurate measurement. The ionic conductivities of the membrane in bromide and carbonate forms at 90 degrees C and 95% RH are found to be 13 and 17 mS cm(-1) respectively. When exchanged with hydroxide, conductivity improved to 86 mS cm(-1) under the same experimental conditions. The effect of relative humidity on water uptake and the SAXS patterns of the AEM membranes were investigated. SAXS analysis revealed a rigid aromatic structure of the AEM membrane with no microphase separation. The synthesized AEM is shown to be mechanically stable as seen from the water uptake and SAXS studies. Diffusion NMR studies demonstrated a steady state long-range diffusion constant, D of 9.8 x 10(-6) cm(2) s(-1) after 50-100 ms. (c) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1743-1750, 2013