Probing the dynamics of particles in an aging dispersion using diffusing wave spectroscopy

Abstract

We have studied theoretically and experimentally the dynamic multiple light scattering properties of a liquid dispersion (an aqueous foam for the experiments) having a continuous phase doped with colloidal scatterers (monodisperse latex beads for the experiments). The temporal auto-correlation function of the scattering intensity shows two characteristic timescales. The slow timescale is related to the reorganization of the dispersion induced by aging, while the fast timescale is related to the Brownian dynamic of the colloids. Although the static light scattering properties are fully controlled by the dispersion at a large scale, the dynamic scattering is surprisingly highly sensitive to even a tiny amount of added colloids. The non-trivial generic behavior discussed here reveals that using multiple light scattering to study complex and real industrial or food-related dispersed products requires special care to avoid possible misinterpretations.