NMR study of the diffusion processes in gels

Stimulated spin-echo and Carr-Purcell pulse sequences, with pulsed magnetic field gradients, have been used to study the self-diffusion processes of the water in swollen and in supercoiled polyacrylamide gels and in polysaccharides agarose gels, for different polymer concentrations. Restricted diffusion effects are evidenced in both types of gels through the time dependence of the diffusion constant. The results can be interpreted in the framework of diffusion model through permeable walls.