Nmr relaxation in Nafion - the low temperature regime

The dynamical characteristics of water absorbed in Nafion are investigated using n.m.r. At temperatures below the dynamical transition temperature, T- t, relaxation rates indicate mobility associated with a fluid but the deriv ed motional activation energies are similar to those of ice. This indicates a well ordered supercooled fluid consisting of hydrogen bonded water struc tures. The correlation time tau(c) is found to have a Gaussian dependence o n the surface area to volume ratio, unlike simple porous systems. We have s hown that the surface area depends on r(2.5) We feel that this is due to th e irregular nature of the surfaces of the clusters. (C) 1999 Published by E lsevier Science Ltd. All rights reserved.