An nmr investigation of the dynamical characteristics of water absorbed in Nafion

Proton and deuterium spin-lattice relaxation times (T-1), spin-spin relaxation times (T-2), and rotating frame spin-lattice relaxation times (T-1 rho) and Fluorine T-1 and T-2 were measured as a function of hydration and temperature in hydrated Nafion. The proton and deuterium data display an apparent dynamical transition which we have attributed to a change in the degree of order within the aqueous phase. The temperature at which this transition occurs, T-t, is a function of the level of hydration, increasing for decreasing hydration. Above T-t, the relaxation processes are similar to those observed in bulk water. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.