Anomalous diffusion of water in a hydrogel of sucrose and diepoxide monomers

This article is concerned with the study of the diffusion of water molecule s in a hydrogel, obtained by controlled hydration of a cross-linked polymer of sucrose and diepoxide monomers. The diffusion measurements were perform ed by means of H-1(NMR) nuclear magnetic resonance techniques in the fringe field of a superconductor magnet with a field gradient G similar or equal to 36.3 T m(-1). This large field gradient and the stimulated echo pulse se quence allows to obtain time-dependent diffusion coefficients and to observ e a non-Debye feature of the relaxation attenuation function. The behavior of the diffusion follows a stretched exponential function plus a Debye term , allowing the determination of different water domains. In the long time l imit the diffusion follows a long tail Levy function, whose asymptotic limi t is related to the fractal dimension of the underlying polymer structure. (C) 2001 American Institute of Physics.