A cluster mode-coupling approach to weak gelation in attractive colloids

TL;DR

This paper extends mode-coupling theory to describe weak gelation in attractive colloids by considering cluster aggregation effects, predicting a semi-ergodic phase with logarithmic relaxation near the gel line.

Contribution

It introduces a two-stage ergodicity breaking framework for weak gelation, combining bare MCT at short scales and MCT on clusters at larger scales.

Findings

Prediction of a long-lived semi-ergodic phase of mobile clusters.

Logarithmic relaxation behavior near the gel line.

Analysis of competition between arrest and phase separation.

Abstract

Mode-coupling theory (MCT) predicts arrest of colloids in terms of their volume fraction, and the range and depth of the interparticle attraction. We discuss how effective values of these parameters evolve under cluster aggregation. We argue that weak gelation in colloids can be idealized as a two-stage ergodicity breaking: first at short scales (approximated by the bare MCT) and then at larger scales (governed by MCT applied to clusters). The competition between arrest and phase separation is considered in relation to recent experiments. We predict a long-lived `semi-ergodic' phase of mobile clusters, showing logarithmic relaxation close to the gel line.