Studies of Water in Nafion Membranes: Dielectric Relaxation and Deuteron and Oxygen-17 NMR.

摘要

Dielectric relaxation and both deuteron and oxygen-17 nuclear magnetic resonance measurements on NAFION-117 membranes with variable water content (approx. 5 - 18 % by weight) are reported. Glassy behavior of the water domains at low T (below approx. 200 K) is evidenced by the specific nature of the observed dielectric loss peaks and 2 H NMR lineshapes. Activation energies extracted from 2 H spin-lattice relaxation data on the high T side of the T sub one minimum exhibit a steady increase with increasing water content. In spite of a high degree of water molecular mobility, angular-dependent spectra in both as-received and stretched samples reflect considerable anisotropy of the host polymer. A dielectric loss peak is observed which has previously been attributed to the glass transition of the aqueous domains.... NAFION, Deuteron and oxygen-17 NMR, Dielectric relaxation, Low T properties, Anisotropic molecular motion.