Collective diffusion in charge-stabilized suspensions: Concentration and Salt Effects

GAPINSKI, J.; PATKOWSKI, A.; BANCHIO, A. J.; HOLMQVIST, P.; MEIER, G.; LETTINGA, M. P.; NÄGELE, G.

JOURNAL OF CHEMICAL PHYSICS

Año: 2007 vol. 126 p. 104905 - 104905

0021-9606

The authors present a joint experimental-theoretical study of collective diffusion properties inaqueous suspensions of charge-stabilized fluorinated latex spheres. Small-angle x-ray scattering andx-ray photon correlation spectroscopy have been used to explore the concentration andionic-strength dependence of the static and short-time dynamic properties including thehydrodynamic function H(q), the wave-number-dependent collective diffusion coefficient D(q), andthe intermediate scattering function over the entire accessible range. They show that allexperimental data can be quantitatively described and explained by means of a recently developedaccelerated Stokesian dynamics simulation method, in combination with a modified hydrodynamicmany-body theory. In particular, the behavior of H(q) for de-ionized and dense suspensions can beattributed to the influence of many-body hydrodynamics, without any need for postulatinghydrodynamic screening to be present, as it was done in earlier work. Upper and lower boundariesare provided for the peak height of the hydrodynamic function and for the short-time self-diffusioncoefficient over the entire range of added salt concentrations.