Interference of dynamical arrest, thermodynamic instabilities and energy-scale competition in symmetric binary mixtures

TL;DR

This paper explores how dynamical arrest and thermodynamic instabilities interact in symmetric binary mixtures, revealing complex amorphous states and extending phase diagram classifications to non-equilibrium conditions.

Contribution

It introduces a unified framework incorporating kinetic arrest and competing instabilities to better understand non-equilibrium states in binary mixtures.

Findings

Dynamical arrest can suppress phase separation in mixtures.

Different regimes lead to distinct arrested states driven by underlying mechanisms.

A structural order parameter $$ describes the crossover between regimes.

Abstract

The equilibrium behavior of binary mixtures can be understood through the competition of energy scales, which classifies their corresponding phase diagrams into distinct topological regimes (Types I-IV). However, in many soft-matter mixtures, strong competing interactions and kinetic barriers often promote dynamical arrest, disrupting the formation of equilibrium and metastable states, and thus rendering conventional phase diagrams incomplete. Here we extend the description and classification of binary systems inside regions of thermodynamical instability. Specifically, we discuss how the interplay between two kind of instabilities and kinetic arrest generates a variety of amorphous states driven by different underlying mechanisms. For strong cross-attraction, for example, dynamical arrest suppresses demixing, whereas in competitive regimes, a mixture may display either condensation-driven or demixing-induced arrested states. The crossover between these regimes can be described by a structural order parameter $\chi$, providing a unified non-equilibrium description that reconciles theoretical predictions with experimentally observed arrested states.