Using patchy particles to prevent local rearrangements in models of non-equilibrium colloidal gels

TL;DR

This paper demonstrates that incorporating directional attractions in particle models prevents lateral rearrangements, leading to gel structures that better match experimental observations of colloidal gels.

Contribution

Introducing directional attractions in particle models to inhibit lateral rearrangements, improving the accuracy of simulated gel structures compared to experimental data.

Findings

Directional attractions lead to more branched gel structures.

Combining isotropic and directional attractions controls aggregation.

Inhibition of lateral rearrangements significantly affects gel topology.

Abstract

Simple models based on isotropic interparticle attractions often fail to capture experimentally observed structures of colloidal gels formed through spinodal decomposition and subsequent arrest: the resulting gels are typically denser and less branched than their experimental counterparts. Here we simulate gels formed from soft particles with directional attractions ("patchy particles"), designed to inhibit lateral particle rearrangement after aggregation. We directly compare simulated structures with experimental colloidal gels made using soft attractive microgel particles, by employing a "skeletonization" method that reconstructs the 3-dimensional backbone from experiment or simulation. We show that including directional attractions with sufficient valency leads to strongly branched structures compared to isotropic models. Furthermore, combining isotropic and directional attractions provides additional control over aggregation kinetics and gel structure. Our results show that the inhibition of lateral particle rearrangements strongly affects the gel topology, and is an important effect to consider in computational models of colloidal gels.