Stabilization of twisted-rope-like domains in the cholesteric mesophase formed by novel cholesterol-based liquid crystal molecules

Abstract

The present work explores a novel cholesterol-based liquid crystal (LC) molecule exhibiting high temperature blue phase III (BPIII), followed by a wide range of cholesteric (N*) mesophases characterized by bright blue colouration arising from Bragg-like selective reflection. As the temperature decreases, N* transitions into the twist grain boundary (TGB_A) mesophase, followed by a smectic A phase. This mesomorphic behaviour is explored using optical and dielectric studies, which show a wide temperature region in which the N* and TGB_A phases co-exist. This co-existence eventually leads to the stabilization of micrometer-sized twisted-rope-like domains. They are observed during the heating cycle in the N* mesophase using a wedge LC cell and exist until the isotropic transition temperature. The stability and length of these twisted domains are found to be dependent on the thickness of the cell and the nature of the alignment layer. This is the first experimental observation of such self-assembled structures being stabilized in the N* mesophase. Such stimuli-controlled micrometer-sized twisted structures open new pathways for tunable optical components, templated self-assembly routes toward chiral micro- and nano-structured materials, and chirality-controlled microstructures.