Photon correlation and sedimentation experiments on interacting PMMA particles in benzene

Abstract

Photon correlation (PCS) experiments on interacting PMMA (polymethylmethacrylate) latexes show the existence of static (thermodynamic) and hydrodynamic interactions. The interactions are observed through the measurement of an effective diffusion coefficient as a function of concentration and scattering wave vector. For the largest particles the wave vector dependence of the effective diffusion coefficient confirms theoretical predictions that from PCS experiments mutual and self-diffusion coefficients can be observed. The combination of PCS experiments with sedimentation experiments enables the separation of hydrodynamic and static interactions. The hydrodynamic interactions contain two physical significant terms which can be deduced separately only by the combination of PCS experiments at large wave vectors with the sedimentation experiments. The combined experimental data show that the interaction is too complicated to be described by simple model potentials of hard sphere repulsion with either an attractive or a repulsive disturbance.