6533b7defe1ef96bd12764f4

RESEARCH PRODUCT

Rotational diffusion of colloid spheres in concentrated suspensions studied by deuteron NMR

subject

description

We present a study of the application of deuteron-nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of spherical colloidal particles. We performed NMR pulse experiments on colloidal suspensions of polystyrene latex spheres in water-glycerol mixtures in a wide range of particle volume fractions \ensuremath{\varphi} from the dilute suspension up to \ensuremath{\varphi}=0.504. We have analyzed the stimulated echo NMR signal in the time domain. The full shape of the orientational correlation function deviates from an exponential behavior in the whole \ensuremath{\varphi} range examined. We evaluate the rotational diffusion coefficient and calculate its \ensuremath{\varphi} dependence up to the ${\mathrm{\ensuremath{\varphi}}}^{2}$ term in view of the theory proposed recently [V. Degiorgio, R. Piazza, and R. B. Jones, Phys. Rev. E 52, 2707 (1995)], which considers the effect of two- and three-body hydrodynamic interactions upon particle reorientation. We find considerable slowing down of sphere reorientation for \ensuremath{\varphi}\ensuremath{\geqslant}0.2. The agreement between experimental results and theoretical considerations is satisfactory.