Demixing behavior in two-dimensional mixtures of anisotropic hard bodies

TL;DR

This paper uses scaled particle theory and bifurcation analysis to predict liquid-crystal demixing in two-dimensional mixtures of anisotropic hard bodies, revealing complex phase behaviors including isotropic-nematic and nematic-nematic demixing.

Contribution

It demonstrates the possibility of isotropic-nematic demixing in 2D mixtures of convex bodies using theoretical and exact calculations, extending understanding of phase behavior in such systems.

Findings

Isotropic-nematic demixing is possible in 2D mixtures.

Nematic-nematic demixing can occur ending in a critical point.

Identified isotropic-nematic-nematic triple point in specific mixtures.

Abstract

Scaled particle theory for a binary mixture of hard discorectangles and for a binary mixture of hard rectangles is used to predict possible liquid-crystal demixing scenarios in two dimensions. Through a bifurcation analysis from the isotropic phase, it is shown that isotropic-nematic demixing is possible in two-dimensional liquid-crystal mixtures composed of hard convex bodies. This bifurcation analysis is tested against exact calculations of the phase diagrams in the framework of the restricted-orientation two-dimensional model (Zwanzig model). Phase diagrams of a binary mixture of hard discorectangles are calculated through the parametrization of the orientational distribution functions. The results show not only isotropic-nematic, but also nematic-nematic demixing ending in a critical point, as well as an isotropic-nematic-nematic triple point for a mixture of hard disks and hard discorectangles.