Short-ranged attractive colloids: What is the gel state ?

TL;DR

This study investigates the properties of short-ranged attractive colloids using a binary mixture model, revealing that gel states are not directly linked to attractive glass transitions but may involve arrested phase separation.

Contribution

It provides a comprehensive comparison of thermodynamic, geometric, and dynamic properties to clarify the nature of gel states in short-range attractive colloids.

Findings

Gel state not directly related to attractive glass transition.

Possible link between gel formation and arrested phase separation.

Short-range attraction may not produce equilibrium cluster phases at low densities.

Abstract

We evaluate thermodynamic, geometric and dynamic properties of a short-ranged square well binary mixture to provide a coherent picture of this simple, but rich, model for colloidal interactions. In particular, we compare the location, in the temperature-packing fraction plane, of the geometrical percolation locus, the metastable liquid-gas spinodal and the glass transition lines. Such comparison provides evidence that the gel-state can not be related to the attractive glass transition line directly. Indications are given for the possibility of an indirect link between the two, via an arrested phase separation process. We finally discuss the possibility that a spherical short range attraction may not be sufficient to produce an equilibrium cluster phase at low packing fraction and low temperatures.