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.