Coupling between criticality and gelation in "sticky" spheres: A structural analysis

TL;DR

This study combines experiments and simulations to analyze how criticality influences gelation in sticky spheres, revealing structural changes and fluctuations near the gas-liquid binodal.

Contribution

It provides a detailed structural analysis linking critical density fluctuations to gelation, using experimental imaging and Monte Carlo simulations mapped onto a square-well model.

Findings

Excellent agreement between experiments and simulations in structural features.

Critical fluctuations drive structural crossover near the binodal.

Arrested spinodal decomposition relates to long-lived structures.

Abstract

We combine experiments and simulations to study the link between criticality and gelation in sticky spheres. We employ confocal microscopy to image colloid-polymer mixtures, and Monte Carlo simulations of the square-well (SW) potential as a reference model. To this end, we map our experimental samples onto the SW model. We find excellent structural agreement between experiments and simulations, both for locally favored structures at the single particle level and large-scale fluctuations at criticality. We follow in detail the rapid structural change of the critical fluid when approaching the gas-liquid binodal and highlight the role of critical density fluctuations for this structural crossover. Our results link the arrested spinodal decomposition to long-lived energetically favored structures, which grow even away from the binodal due to the critical scaling of the bulk correlation length and static susceptibility.