Dynamical Arrest in Attractive Colloids: The Effect of Long-Range Repulsion

TL;DR

This study investigates gelation in colloidal suspensions with short-range attraction and long-range repulsion, revealing that gelation involves cluster growth into anisotropic chains and face-sharing tetrahedral structures, leading to dynamical arrest.

Contribution

It provides new insights into the microscopic structure and formation process of gels in colloids with competing interactions, highlighting the role of cluster and chain formation.

Findings

Gels form from dense chains of face-sharing tetrahedral clusters.

Cluster growth and association drive dynamical arrest.

The gel structure exhibits surprising order with anisotropic chains.

Abstract

We study gelation in suspensions of model colloidal particles with short-ranged attractive and long-ranged repulsive interactions by means of three-dimensional fluorescence confocal microscopy. At low packing fractions, particles form stable equilibrium clusters. Upon increasing the packing fraction the clusters grow in size and become increasingly anisotropic until finally associating into a fully connected network at gelation. We find a surprising order in the gel structure. Analysis of spatial and orientational correlations reveals that the gel is composed of dense chains of particles constructed from face-sharing tetrahedral clusters. Our findings imply that dynamical arrest occurs via cluster growth and association.