One-dimensional cluster growth and branching gels in colloidal systems with short-range depletion attraction and screened electrostatic repulsion

TL;DR

This study uses numerical simulations to explore how charged colloidal particles with short-range attraction and screened electrostatic repulsion form one-dimensional clusters and branching gels, revealing mechanisms of gelation at specific screening lengths.

Contribution

It introduces a detailed simulation model for charged colloids with combined attractive and repulsive interactions, highlighting the formation of quasi one-dimensional clusters and branching gels at certain screening lengths.

Findings

Particles form quasi one-dimensional clusters at low temperature.

Branching mechanisms lead to macroscopic gel formation.

Results align with recent experimental observations.

Abstract

We report extensive numerical simulations of a simple model for charged colloidal particles in suspension with small non-adsorbing polymers. The chosen effective one-component interaction potential is composed of a short-range attractive part complemented by a Yukawa repulsive tail. We focus on the case where the screening length is comparable to the particle radius. Under these conditions, at low temperature, particles locally cluster into quasi one-dimensional aggregates which, via a branching mechanism, form a macroscopic percolating gel structure. We discuss gel formation and contrast it with the case of longer screening lengths, for which previous studies have shown that arrest is driven by the approach to a Yukawa glass of spherical clusters. We compare our results with recent experimental work on charged colloidal suspensions [A. I. Campbell {\it et al.} cond-mat/0412108, Phys. Rev. Lett. in press].