ABSTRACT We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nuclei (7Li, 23Na) and 1H pulsed field gradients NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The structure of these clay dispersions consists of a porous network limited by the clay/water solid/liquid interfaces. NMR relaxometry leads to new information on the local ordering occurring in dilute and macroscopically isotropic dispersions of synthetic Laponite clay. In contrast, the NMR spectra of the quadrupolar nuclei and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation on the basis of the structure of the clay dispersions and an atomic description of the clay/water and clay/ion interactions
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