Phase diagram of Janus Particles

TL;DR

This paper models Janus particles, revealing their phase behavior including phase separation and micellization, and suggests they exhibit anomalous thermodynamic properties similar to some complex fluids.

Contribution

It introduces a simple model capturing both micellization and phase separation in Janus particles, a phenomenon not previously observed together in a single model.

Findings

Phase diagram shows gas-liquid coexistence and micellization.

Micellization suppresses phase separation.

Coexistence curve is negatively sloped in T-P plane.

Abstract

We deeply investigate a simple model representative of the recently synthesized Janus particles, i.e. colloidal spherical particles whose surface is divided into two areas of different chemical composition. When the two surfaces are solvophilic and solvophobic, these particles constitute the simplest example of surfactants. The phase diagram includes a colloidal-poor (gas) colloidal-rich (liquid) de-mixing region, which is progressively suppressed by the insurgence of micelles, providing the first model where micellization and phase-separation are simultaneously observed. The coexistence curve is found to be negatively sloped in the temperature-pressure plane, suggesting that Janus particles can provide a colloidal system with anomalous thermodynamic behavior.