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

Abstract

International audienceWe 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

Interplay of coarsening, aging, and stress hardening impacting the creep behavior of a colloidal gel

“…This strongly suggests that this decay is indeed due to the motion of a small fraction of single particles that are not yet part of the network. The decreasing magnitude of the intermediate decay with sample age indicates that the number of these mobile particles is a decreasing function of the age of the sample [51,52]. We can thus conclude that the temporal .…”

Spectral Properties of Foams and Emulsions

“…DWS analysis of the coarsening of an aqueous foam loaded with monodisperse latex beads revealed that the temporal autocorrelation function of the scattering intensity presents two decays decoupled and separated in time. These distinct decays are due to two different processes: bubble rearrangements during foam ageing, which is responsible for the longer decay, and Brownian motion of the colloidal particles in the liquid fraction, giving rise to the shorter decay [121].…”

Tracking of wet foam ageing by means of dynamic laser speckle and computer optical mouse

“…The other mechanism is due to gradients of pressure, between inner and outer of the bubble, driving the gas from smaller bubbles to greater bubbles [1,2]. Several experimental techniques and theoretical models have been proposed exploring the properties and complex dynamics of foams, which have some aspect of physical chemist that are unclear and motivate new procedures to understand the dynamics of this material [3,4].…”