Intermittent dynamics and logarithmic domain growth during the spinodal decomposition of a glass-forming liquid

TL;DR

This study uses large-scale molecular dynamics simulations to explore how temperature influences phase separation kinetics in a glass-forming liquid, revealing a transition from diffusive to intermittent, slow domain growth as the system approaches a glassy state.

Contribution

It demonstrates the temperature-dependent transition in phase separation dynamics, highlighting the microscopic mechanisms behind arrested spinodal decomposition in glass-forming liquids.

Findings

High-temperature phase separation driven by surface tension and diffusion.

Low-temperature dynamics become intermittent and thermally activated.

Logarithmic growth of domain size at low temperatures.

Abstract

We use large-scale molecular dynamics simulations of a simple glass-forming system to investigate how its liquid-gas phase separation kinetics depends on temperature. A shallow quench leads to a fully demixed liquid-gas system whereas a deep quench makes the dense phase undergo a glass transition and become an amorphous solid. This glass has a gel-like bicontinuous structure that evolves very slowly with time and becomes fully arrested in the limit where thermal fluctuations become negligible. We show that the phase separation kinetics changes qualitatively with temperature, the microscopic dynamics evolving from a surface tension-driven diffusive motion at high temperature to a strongly intermittent, heterogeneous and thermally activated dynamics at low temperature, with a logarithmically slow growth of the typical domain size. These results shed light on recent experimental observations of various porous materials produced by arrested spinodal decomposition, such as nonequilibrium colloidal gels and bicontinuous polymeric structures, and they elucidate the microscopic mechanisms underlying a specific class of viscoelastic phase separation.