Depletion-induced biaxial nematic states of boardlike particles

TL;DR

This study explores how adding non-adsorbing depletants influences the phase stability of biaxial nematic liquid crystals formed by colloidal boardlike particles, revealing a tunable pathway to stabilize biaxial nematic phases.

Contribution

It introduces a mean-field theoretical framework to predict how depletant density can induce and control biaxial nematic order in colloidal particles.

Findings

A critical depletant density triggers a direct isotropic to biaxial nematic transition.

Depletant tuning stabilizes biaxial nematic phases otherwise unstable in pure systems.

The model provides a controllable experimental parameter for liquid crystal phase manipulation.

Abstract

With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of the depletant by introducing an effective depletion attraction between a pair of boardlike particles. At fixed depletant fugacity, the stable liquid crystal phase is determined through a mean-field theory with restricted orientations. Interestingly, we predict that for slightly elongated boardlike particles a critical depletant density exists, where the system undergoes a direct transition from an isotropic liquid to a biaxial nematic phase. As a consequence, by tuning the depletant density, an easy experimental control parameter, one can stabilize states of high biaxial nematic order even when these states are unstable for pure systems of boardlike particles.