Nematic ordering of suspension of charged anisotropic colloids detected by multinuclear quadrupolar spectra and 1H PGSE-NMR measurements.
The structure of aqueous dispersion of charged anisotropic nano-composites (synthetic Laponite clays) have been studied by NMR and numerical simulations based on a multi-scale statistical analysis have been used to interpret the mobility of the confined water molecule diffusing within dense Laponite aqueous dispersions (29-52% w/w) prepared by uniaxial compression. Firstly, the lineshape detected by NMR quadrupolar spectroscopy of the counterions ((23)Na or (7)Li) exhibits a large residual splitting Delta nu which is the fingerprint of the macroscopic nematic ordering of the anisotropic particles. Secondly, these results are also confirmed by the anisotropy of the self-diffusion tensor of the water molecule measured by (1)H Pulsed Gradient Spin Echo NMR. This self-diffusion anisotropy increases with the suspension density. Thirdly, the multi-scale statistical analysis of the water mobility bridges the gap between the time-scale (ps) accessible by Molecular Dynamics simulations and the time-scale (micros) accessible by Brownian Dynamics, leading to macroscopic behaviour comparable with PGSE-NMR data measurements.
Porion
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P
Centre de Recherche sur la Matière Divisée, UMR 6619 CNRS-Université d'Orléans, 45071 Orléans Cedex 2, France. porion@cnrs-orleans.fr
Al-Mukhtar
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M
Faugère
A-M
AM
Meyer
S
S
Delville
A
A