Dynamical heterogeneities close to a colloidal gel

TL;DR

This study uses computer simulations to analyze dynamical heterogeneities near colloidal gelation, revealing two distinct particle populations with different mobilities and structural roles within the gel.

Contribution

It provides a detailed characterization of the static and dynamic properties of fast and slow particles in colloidal gels near gelation, highlighting their structural and dynamical differences.

Findings

Fast particles form a network of mobile regions.

Slow particles create a stuck, networked structure.

Fast particles relax environment faster than slow ones.

Abstract

Dynamical heterogeneities in a colloidal fluid close to gelation are studied by means of computer simulations. A clear distinction between some fast particles and the rest, slow ones, is observed, yielding a picture of the gel composed by two populations with different mobilities. Analyzing the statics and dynamics of both sets of particles, it is shown that the slow particles form a network of stuck particles, whereas the fast ones are able to move over long distances. Correlation functions show that the environment of the fast particles relaxes much faster than that of the slow ones, but at short times the bonds between fast particles are longer lived due to the flexibility of their structure. No string-like motion is observed for the fast particles, but they occupy preferential sites in the surface of the structure formed by the slow ones.