Demixing, remixing and cellular networks in binary liquids containing colloidal particles

TL;DR

This study uses confocal microscopy to investigate how colloidal particles stabilize emulsions and form cellular networks during demixing and remixing in binary liquids, revealing mechanisms that could enable advanced material fabrication.

Contribution

It demonstrates the formation and stabilization of colloidal cellular networks in binary liquids, highlighting the role of interfacial particles and pressure balance in these processes.

Findings

Colloidal particles stabilize emulsions mainly through interfacial adsorption.

Cellular networks form just before remixing, stabilized by high colloid concentration.

Networks can be maintained for over 30 minutes, enabling material applications.

Abstract

We present a confocal-microscopy study of demixing and remixing in binary liquids containing colloidal particles. First, particle-stabilized emulsions have been fabricated by nucleation and growth of droplets upon cooling from the single-fluid phase. We show that their stability mainly derives from interfacial particles; the surplus of colloids in the continuous phase possibly provides additional stability. Upon heating these emulsions, we have observed the formation of polyhedral cellular networks of colloids, just before the system remixes. Given a suitable liquid-liquid composition, the initial emulsions cross the binary-liquid symmetry line due to creaming. Therefore, upon heating, the droplets do not shrink and they remain closely packed. The subsequent network formation relies on a delicate balance between the Laplace pressure and the pressure due to creaming/remixing. As high concentrations of colloids in the cell walls inhibit film thinning and rupture, the networks can be stabilized for more than 30 minutes. This opens up an avenue for their application in the fabrication of advanced materials.