Observation of empty liquids and equilibrium gels in a colloidal clay

TL;DR

This study provides the first experimental evidence of empty liquids and equilibrium gels in a colloidal clay, confirming theoretical predictions and advancing the understanding of anisotropic interactions in soft materials.

Contribution

The paper experimentally demonstrates the existence of empty liquids and equilibrium gels in colloidal clay, supporting recent theoretical models and simulations.

Findings

Observation of empty liquids in colloidal clay

Detection of equilibrium gels without phase separation

Numerical simulations corroborate experimental results

Abstract

The relevance of anisotropic interactions in colloidal systems has recently emerged in the context of the rational design of new soft materials. Patchy colloids of different shapes, patterns and functionalities are considered the new building blocks of a bottom-up approach toward the realization of selfassembled bulk materials with predefined properties. The ability to tune the interaction anisotropy will make it possible to recreate molecular structures at the nano- and microscales (a case with tremendous technological applications), as well as to generate new unconventional phases, both ordered and disordered. Recent theoretical studies suggest that the phase diagram of patchy colloids can be significantly altered by limiting the particle coordination number (that is, valence). New concepts such as empty liquids-liquid states with vanishing density-and equilibrium gels arrested networks of bonded particles, which do not require an underlying phase separation to form-have been formulated. Yet no experimental evidence of these predictions has been provided. Here we report the first observation of empty liquids and equilibrium gels in a complex colloidal clay, and support the experimental findings with numerical simulations.