A molecular dynamics study of chemical gelation in a patchy particle model

TL;DR

This study uses molecular dynamics simulations to analyze chemical gelation in a patchy particle model, demonstrating the accuracy of mean-field predictions and the relevance of the model to various soft materials.

Contribution

It provides the first detailed simulation-based validation of mean-field theories for irreversible gelation in asymmetric patchy particles.

Findings

Mean-field predictions are accurate over a large reaction extent range.

Flory's hypothesis describes post-gelation cluster connectivity.

The model closely mimics real soft materials with network formation.

Abstract

We report event-driven molecular dynamics simulations of the irreversible gelation of hard ellipsoids of revolution containing several associating groups, characterizing how the cluster size distribution evolves as a function of the extent of reaction, both below and above the gel point. We find that in a very large interval of values of the extent of reaction, parameter-free mean-field predictions are extremely accurate, providing evidence that in this model the Ginzburg zone near the gel point, where non-mean field effects are important, is very limited. We also find that the Flory's hypothesis for the post-gelation regime properly describes the connectivity of the clusters even if the long-time limit of the extent of reaction does not reach the fully reacted state. This study shows that irreversibly aggregating asymmetric hard-core patchy particles may provide a close realization of the mean-field model, for which available theoretical predictions may help control the structure and the connectivity of the gel state. Besides chemical gels, the model is relevant to network-forming soft materials like systems with bioselective interactions, functionalized molecules and patchy colloids.