On the analysis of the effective adhesion in colloidal dispersions in the sticky hard sphere model

Abstract

Structural trends in multicomponent mixtures of adhesive spheres are analyzed by using the Baxter formalism and the Percus–Yevick approximation (PYA). The Orsnstein–Zernike (OZ) equations in q space are cast in a form which allows a fully analytical expression of the effective adhesiveness coefficient of the large (solute) spheres in the asymptotic limit of vanishing size ratio and no solute self-stickiness. This allows a simple discussion of the factors which determine the effective solute adhesiveness and suspension stability: while the steric effect and like particles stickiness are found to favor suspension instability, hetero stickiness is found to act in one side or in the opposite depending on the concentration of the smaller species. These qualitative predictions are paralleled with studies on solvent effects in ordinary colloidal solute–solvent systems and with the behavior of pseudobinary systems such as colloid–polymer or bidisperse colloidal mixtures. Results from the literature for hard sphere mixtures and calculations in the PYA including solute self-stickiness at nonzero size ratio are finally used to discuss the reliability of the trends deduced from the asymptotic limit.