Lattice elasticity of blue phases in cholesteric liquid crystals

TL;DR

This paper develops theoretical models within Landau-de Gennes framework to analyze the elastic properties of cubic blue phases in cholesteric liquid crystals, highlighting the need for further experimental validation.

Contribution

It introduces a new theoretical approach to calculate elastic moduli of blue phases, focusing on the simplest cubic phase and comparing different approximation methods.

Findings

Calculated bulk and shear moduli depend on chirality and temperature.

Rigid tensor and free helicoid approximations yield similar qualitative but different quantitative results.

Further experimental and numerical studies are needed for validation.

Abstract

New theoretical approaches have been developed for studying and quantitatively describing the elastic properties of cubic blue phases in cholesteric liquid crystals. Within the framework of the Landau-de Gennes theory, using the simplest blue phase with spatial group $O^5$ ($I432$) as an example, calculations of the bulk modulus and two shear moduli were performed depending on the chirality strength and temperature below the crystallization point from isotropic liquid. It is shown that the used approximations of rigid tensors and free helicoids give qualitatively similar results but differ noticeably quantitatively, therefore further experimental studies and numerical modeling of blue phase elasticity are necessary.