Dynamics of monodisperse and bidisperse polymer latices

Abstract

Dynamic properties of monodisperse and bimodal mixtures of electrostatically stabilized polymer latices have been studied at high concentration. Macroscopic properties were measured by rheometry and viscous as well as elastic behavior was investigated. Information on particle diffusion was obtained by means of fiber optical quasi elastic light scattering (FOQELS). In monodisperse systems, short time self-diffusion of particles at high ionic strength could be described by theoretical calculations for hard spheres although shear viscosity showed deviations from hard sphere behavior. Elastic properties were observed by rheology at high volume fractions and the existence of a yield stress could also be optically detected by FOQELS. In bimodal mixtures, a “probe diffusion”, i.e., diffusion of a small number of large spheres in a matrix of small particles could be measured by FOQELS. Probe diffusion was strongly slowed down with increasing volume fraction and the concentration dependence was similar to that of viscosity. Variation of particle size ratio and composition allowed for the possibility to measure diffusion of small and/or large particles in the mixture by FOQELS.