Dynamics of Uniaxial-to-Biaxial Nematics Switching in Suspensions of Hard Cuboids

TL;DR

This study uses Dynamic Monte Carlo simulations to explore how external fields induce uniaxial-to-biaxial nematic phase switching in suspensions of hard cuboids, revealing the influence of particle shape and anisotropy on response times.

Contribution

It provides new insights into the reorientation dynamics of cuboidal colloids under external fields, highlighting the unexpected slow response of self-dual shapes compared to prolate particles.

Findings

Response time correlates with particle anisotropy.

Self-dual cuboids exhibit slower reorientation despite theoretical suitability.

External stimuli can induce phase switching at the particle level.

Abstract

Field-induced reorientation of colloidal particles is especially relevant to manipulate the optical properties of a nanomaterial for target applications. We have recently shown that surprisingly feeble external stimuli are able to transform uniaxial nematic liquid crystals (LCs) of cuboidal particles into biaxial nematic LCs. In the light of these results, here we apply an external field that forces the reorientation of colloidal cuboids in nematic LCs and sparks a uniaxial-to-biaxial texture switching. By Dynamic Monte Carlo simulation, we investigate the unsteady-state reorientation dynamics at the particle scale when the field is applied (uniaxial-to-biaxial switching) and then removed (biaxial-to-uniaxial switching). We detect a strong correlation between the response time, being the time taken for the system to reorient, and particle anisotropy, which spans from rod-like to plate-like geometries. Interestingly, self-dual shaped cuboids, theoretically considered as the most suitable to promote phase biaxiality for being exactly in between prolate and oblate particles, exhibit surprisingly slow response times, especially if compared to prolate cuboids.