Dynamical properties of ions confined within dense dispersions of charged anisotropic colloids : A 23Na quadrupolar NMR study
Centre de Recherche sur la Matière Divisée, UMR 6619, CNRS, Université d'Orléans, 1b rue de la Férollerie, 45071 Orléans Cedex 02, France
We used 23Na quadrupolar NMR spectroscopy and relaxation measurements to determine the mobility of the sodium counterions confined within dense aqueous dispersions of synthetic Laponite clays as a model of charged anisotropic nano-composite colloids. The lineshape analysis of the 23Na spectra and the measurements of the Hahn echo attenuation are used to determine the critical clay concentration corresponding to the nematic organisation of the dispersion. As validated by numerical simulations of the ion diffusion within partially oriented nematic dispersion of the anisotropic colloids, the angular variation of the apparent relaxation rates is interpreted as an indice of degree of ordering of the dispersion.
© EDP Sciences, Springer-Verlag, 2007