Nonequilibrium continuous phase transition in colloidal gelation with short-range attraction

TL;DR

This study reveals that colloidal gelation with short-range attraction is a nonequilibrium continuous phase transition driven by percolation, characterized by diverging cluster sizes and broken detailed balance, unifying structural arrest and yielding.

Contribution

It demonstrates that colloidal gelation is governed by a nonequilibrium percolation process with specific critical exponents, combining experiments, simulations, and analytical modeling.

Findings

Cluster sizes diverge with exponent 1.6

Correlation lengths diverge with exponent 0.8

Cluster mass distributions follow power-law behavior

Abstract

The dynamical arrest of attractive colloidal particles into out-of-equilibrium structures, known as gelation, is central to biophysics, materials science, nanotechnology, and food and cosmetic applications, but a complete understanding is lacking. In particular, for intermediate particle density and attraction, the structure formation process remains unclear. Here, we show that the gelation of short-range attractive particles is governed by a nonequilibrium percolation process. We combine experiments on critical Casimir colloidal suspensions, numerical simulations, and analytical modeling with a master kinetic equation to show that cluster sizes and correlation lengths diverge with exponents 1.6 and 0.8, respectively, consistent with percolation theory, while detailed balance in the particle attachment and detachment processes is broken. Cluster masses exhibit power-law distributions with exponents -3/2 and -5/2 before and after percolation, as predicted by solutions to the master kinetic equation. These results revealing a nonequilibrium continuous phase transition unify the structural arrest and yielding into related frameworks.