Dynamic correlations between charged colloidal particles: Coupled macroion–counterion diffusion

A simple theory is presented which predicts the main short‐time and long‐time features observed in the intermediate scattering function F(k,t) measured in experiments of quasielastic light scattering by suspensions of highly charged polystyrene macroparticles. This theory is based on the description of the coupled diffusion of the macroparticles and their counterions by the linear laws of irreversible thermodynamics, and on the use of spatially nonlocal thermodynamic relations to describe the spatial correlations between the diffusing particles.