Extending the Flory-Huggins Theory for Crystalline Multicomponent Mixtures

TL;DR

This paper develops an extended Flory-Huggins model that incorporates crystallization effects in multicomponent mixtures, enabling better prediction of phase behavior in systems where both amorphous and crystalline phases interact.

Contribution

It introduces a generalized free energy model that couples crystallization with amorphous phase separation, expanding the applicability of Flory-Huggins theory to crystalline multicomponent systems.

Findings

Derived a comprehensive free energy model for crystalline mixtures.

Analyzed binary and ternary phase diagrams with the new framework.

Highlighted the interplay between crystallization and phase separation processes.

Abstract

The Flory-Huggins theory is a well-established lattice model that is commonly used to study the mixing of distinct chemical species. It can successfully predict phase separation phenomena in blends of incompatible materials. However, it is limited to amorphous mixtures, excluding systems where the phase segregation is shaped by the concurrent crystallization of one or several blend components. A generalization of the Flory-Huggins formalism is thus necessary to capture the coupling and the interplay of crystallization with amorphous demixing mechanisms, such as spinodal decomposition. This work therefore revolves around the derivation of a free energy model for multicomponent mixtures that encompasses the physics of both processes. It is detailed which concepts from the original Flory-Huggins theory are required to apprehend the presented developments and how the current framework is built upon them. Furthermore, additional discussion points address chemical potential calculations and selected examples of binary and ternary phase diagrams, thereby highlighting the variety of blend behaviors that can be represented.