1H NMR study of the structure and dynamics of water confined between wetting solids

1H NMR relaxation measurements in a broad range of frequencies give information on the dynamical behaviour of water molecules in dilute suspensions of swelling clay (Hectorite). The logarithmic frequency variation of the longitudinal relaxation rate suggests a 2D diffusion of the water molecules adsorbed on the clay particles, with a residence time as long as 10−6 s. The corresponding high activation free energy (40 kJ/mol) originates mainly from the clay-water interactions, as shown by Monte Carlo simulations of clay hydration.