Depletion potential in colloidal mixtures of hard spheres and platelets

TL;DR

This study investigates how the depletion potential between two hard spheres is affected by a solvent of thin hard platelets, using theoretical approaches to understand density-dependent effects and phase behavior.

Contribution

It introduces a density functional theory approach combined with the Derjaguin approximation to analyze depletion potentials in colloidal mixtures of spheres and platelets, highlighting the impact of platelet density.

Findings

Depletion potential deepens with increasing platelet density.

A small repulsive barrier develops at larger sphere separations.

The primary minimum diminishes as the sphere-to-platelet size ratio decreases.

Abstract

The depletion potential between two hard spheres in a solvent of thin hard disclike platelets is investigated by using either the Derjaguin approximation or density functional theory. Particular attention is paid to the density dependence of the depletion potential. A second-order virial approximation is applied, which yields nearly exact results for the bulk properties of the hard-platelet fluid at densities two times smaller than the density of the isotropic fluid at isotropic-nematic phase coexistence. As the platelet density increases, the attractive primary minimum of the depletion potential deepens and an additional small repulsive barrier at larger sphere separations develops. Upon decreasing the ratio of the radius of the spheres and the platelets, the primary minimum diminishes and the position of the small repulsive barrier shifts to smaller values of the sphere separation.