The role of quench rate in colloidal gels

TL;DR

This study uses simulations to show that controlling the quench rate in colloidal gel formation influences local order and stability, with slower quenching promoting crystallinity and more stable gels.

Contribution

It demonstrates how in-situ control of interactions during quenching affects gel structure and stability, revealing the importance of quench rate in colloidal gelation.

Findings

Slower quenching increases local order in gels.

Controlled quenching can induce local crystallisation.

Higher local order correlates with increased gel stability.

Abstract

Interactions between colloidal particles have hitherto usually been fixed by the suspension composition. Recent experimental developments now enable the control of interactions \emph{in-situ}. Here we use Brownian dynamics simulations to investigate the effect of controlling interactions on gelation, by "quenching" the system from an equilibrium fluid to a gel. We find that, contrary to the normal case of an instantaneous quench, where the local structure of the gel is highly disordered, controlled quenching results in a gel with a higher degree of local order. Under sufficiently slow quenching, local crystallisation is found, which is strongly enhanced when a monodisperse system is used. The higher the degree of local order, the smaller the mean squared displacement, indicating an enhancement of gel stability.