Coupling effect of solvent–colloid interaction on diffusivity and viscosity of colloidal hard-sphere suspensions: Statistical mechanical free-volume approach

Abstract

Apart from describing the transport behaviors to a reliable accuracy, it remains as yet far from satisfactory to comprehend the explicit role of the solvent–colloid interaction on the diffusivity and viscosity of colloidal hard-sphere suspensions. Here, we exploit the free volume effect on the diffusivity and viscosity by means of statistical mechanics, which enables to express them in terms of the solvent–solvent, colloid–colloid, and solvent–colloid pair correlation functions as a function of the colloidal concentration. The agreement between the theory and experiment is found to be very good over the entire colloidal volume fraction ϕ investigated by experiment, i.e., up to ϕ∼0.60. The present theory predicts a crossover in the solvent effect on the diffusivity: Above ϕc=0.38, the solvent–colloid interaction enhances the diffusivity of the colloidal particles suspended therein, whereas below ϕc, it serves as a diffusion barrier against the particles.