Clustering and gelation of hard spheres induced by the Pickering effect

TL;DR

This study uses Brownian dynamics simulations to explore how adding emulsion droplets to hard-sphere suspensions induces phase separation, clustering, and gelation, aligning well with recent experimental observations.

Contribution

It demonstrates that nonwetting emulsion droplets can induce phase separation and gelation in hard-sphere suspensions through surface coverage effects.

Findings

Addition of droplets causes gas-liquid and fluid-solid phase separations.

Stable clusters form due to surface saturation of droplets.

Percolation transition leads to gel-like networks.

Abstract

A mixture of hard-sphere particles and model emulsion droplets is studied with a Brownian dynamics simulation. We find that the addition of nonwetting emulsion droplets to a suspension of pure hard spheres can lead to both gas-liquid and fluid-solid phase separations. Furthermore, we find a stable fluid of hard-sphere clusters. The stability is due to the saturation of the attraction that occurs when the surface of the droplets is completely covered with colloidal particles. At larger emulsion droplet densities a percolation transition is observed. The resulting networks of colloidal particles show dynamical and mechanical properties typical of a colloidal gel. The results of the model are in good qualitative agreement with recent experimental findings [E. Koos and N. Willenbacher, Science 331, 897 (2011)] in a mixture of colloidal particles and two immiscible fluids.