Shape Bistability in Squeezed Chromonic Droplets

TL;DR

This paper predicts and confirms the existence of shape bistability in squeezed chromonic liquid crystal droplets, showing coexistence of tactoid and discoid shapes, supported by theoretical modeling and experimental data analysis.

Contribution

It introduces a two-dimensional theoretical model predicting shape bistability in chromonic droplets, aligning with experimental observations and estimating surface tension.

Findings

Bistability between tactoid and discoid shapes predicted

Model agrees quantitatively with experimental data

Estimated surface tension at nematic/melt interface

Abstract

We study droplets of chromonic liquid crystals squeezed between parallel plates inducing degenerate tangential anchoring on the nematic director. In the coexistence regime, where droplets in the nematic phase are at equilibrium with the surrounding melt, our two-dimensional theoretical model predicts a regime of shape bistability for sufficiently large bipolar droplets, where tactoids (pointed shapes) and discoids (smooth shapes) coexist in equilibrium. This phenomenon has not yet been observed. Two-dimensional droplets of disodium cromoglycate (DSCG) have been the object of a thorough experimental study [Y.-K. Kim et al., J. Phys.: Condens. Matter 25, 404202 (2013)]. We show that our theory is in good quantitative agreement with these data and extract from them what promises to be a more accurate estimate for the isotropic surface tension at the nematic/melt interface of DSCG.