Morphological evolution during liquid-liquid phase separation governed by composition change pathways

Abstract

Liquid-liquid phase separation (LLPS) phenomenon are widely recognized to be of vital importance for physics, materials science, and biology. It is highly desired to develop powerful tools to study the LLPS behavior and related physical mechanisms. For this purpose, a phase-field method was developed here which combines the Cahn-Hilliard diffusion equation and the Navier-Stokes equation. The morphological evolution of LLPS behavior with the change in composition was comprehensively investigated under a prototypical ternary theoretical phase diagram. The phase-field simulation results indicated that the microstructural evolution was controlled by the phase diagram and driven by the coupling of diffusion and gravity effect. Moreover, the intermediate morphological microstructures and corresponding interfacial properties during LLPS could be tuned by selecting different composition change pathways. Furthermore, gravity-dependent density overturning and consequent Rayleigh-Taylor instability were observed in a unique LLPS process, demonstrating that the proposed model can capture the critical features of LLPS phenomenon.