Abstract
1H relaxation and pulsed-gradient NMR techniques have been used to probe solvent mobility and binding in aqueous suspensions of Laponite, a synthetic Hectorite clay. The ionic strength and the particle concentration were varied in wide ranges in order to explore the phase diagram. Increasing either one of these parameters is known to induce a sol–soft solid rheological transition. However, neither the proton relaxation rates, R1 and R2, nor the water self-diffusion coefficient, D, were found to be affected by this transition. Only a continuous increase of R1 and R2 and a continuous decrease of D were observed as the particle concentration was increased, whatever the ionic strength. The results are discussed in terms of obstruction to diffusion and surface hydration, in the fast exchange regime. Specific effects due to the particle anisotropy and surface heterogeneity are evidenced.
Published Version
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