High pressure studies of hydrated NAFION membranes: Dielectric relaxation and deuteron NMR

Abstract

Audio frequency electrical conductivity/dielectric relaxation and nuclear magnetic resonance studies of NAFION-117 have been carried out at pressures up to 0.3 GPa (3 kbar). For some samples, the electrical conductivity exhibits dispersion typical of hopping conductivity in an amorphous material, ?=?0?m. The values of m are sample dependent and vary from about 0.55 to 0.75. In addition, the values of m are not strongly pressure sensitive. At a given frequency, the electrical conductivity tends to decrease as pressure increases and yield activation volumes on the order of 5 to 10 cm3/mol. The activation volume determined from the NMR spin-lattice relaxation time measurements are also sample dependent. The data shown correspond to an activation volume of about 8.6 cm3/mol. The results of the high pressure electrical conductivity studies also yield activation volumes on the order of that determined via NMR.