STRUCTURE AND PROPERTIES OF HYDROCARBON IONOMER MEMBRANES .1. POLY(METHYL METHACRYLATE-CO-METHACRYLIC ACID)

A series of poly(methyl methacrylate-co-methacrylic acid) polymer memb ranes with increasing ionic content were prepared and evaluated. DMTA measurements reveal that dry Cs+ samples are not phase separated up to 10 mol% of ionic comonomer. In aqueous solution, a sharp insulator-co nductor transition is observed at about 6.5 mol% of ionic comonomer, w hich is accompanied by the appearance of strongly hydrogen bonded wate r in the membrane. Three distinct types of sorbed water were detected, and two of these appear to be involved in the ionic conduction pathwa ys. Diffusion coefficients for simple ions are large, but smaller than those for perfluorinated ionomers with similar ionic contents.