COMPARISON BETWEEN VISCOSITY AND DIFFUSION IN MONODISPERSE AND BIMODAL COLLOIDAL SUSPENSIONS

Monodisperse and bimodal electrostatically stabilized polymer latices have been investigated with respect to shear viscosity and diffusion. The zero shear viscosity of monodisperse latices could be described by a recent model by Quemada that takes into account the order-disorder transition known from hard-spheres. The high shear viscosity of bimoda l latices prepared by mixing monodisperse samples could be calculated from the data of the monodisperse latices by use of a model by d'Haene and Mewis. Diffusion coefficients in concentrated colloidal suspensio n were obtained by means of fiber optic quasielastic light scattering. With large particles short time self-diffusion was observed, but coll ective diffusion and long time self-diffusion were found in the case o f small colloidal particles. In bimodal latices a probe diffusion of l arge particles in a matrix of small spheres was observed. Long time se lf-diffusion and probe diffusion showed a similar concentration depend ence as reciprocal shear viscosity.