Phase separation of stable colloidal clusters

TL;DR

This paper develops a nonequilibrium thermodynamic theory for colloidal cluster pattern formation, predicting gel networks and phase separation suppression based on cluster stability and reaction kinetics.

Contribution

It introduces a novel mean-field framework incorporating variable gradient energy and cluster stability effects into pattern formation analysis.

Findings

Observable gel patterns and system-spanning networks predicted.

Cluster stability suppresses bulk phase separation.

Pattern formation controlled by Damköhler number and cluster stability.

Abstract

This Article presents a nonequilibrium thermodynamic theory for the mean-field precipitation, aggregation and pattern formation of colloidal clusters. A variable gradient energy coefficient and the arrest of particle diffusion upon "jamming" of cluster aggregates in the spinodal region predicts observable gel patterns that, at high inter-cluster attraction, form system-spanning, out-of-equilibrium networks with glass-like, quasi-static structural relaxation. For reactive systems, we incorporate the free energy landscape of stable pre-nucleation clusters into the Allen-Cahn-Reaction equation. We show that pattern formation is dominantly controlled by the Damk\"ohler number and the stability of the clusters, which modifies the auto-catalytic rate of precipitation. As clusters individually become more stable, bulk phase separation is suppressed.