Nuclear relaxation of liquids in confinements

NMR relaxation studies of porous sol-gel glasses

2H relaxation times T1, T1 rho and T2 for D2O in silica sol-gels are used to monitor porosity and surface interactions within the silica framework as a function of aging. Tetramethoxysilane gels are compared with composites containing low levels of poly(vinyl alcohol) (PVA) prepared under acidic conditions. Non-exponential decay of magnetisation in T1 rho and T2 experiments is attributed to the fractal nature of the pore structure.

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.