Theoretical models for the nematic twist-bend phase and the Landau de Gennes theory of Longa and Tomczyk

We present a critical analysis of the existing phenomenological theories of the nematic twist-bend phase including the models proposed by Dozov and Selinger and the more general Landau de Gennes theory of L. Longa and W. Tomczyk. The role of the flexoelectric polarisation is considered in detail as...

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Bibliographic Details
Published in:Liquid crystals 2024-05, Vol.51 (6), p.948-960
Main Author: Osipov, M. A.
Format: Article
Language:English
Subjects:
bend elastic constant
Elastic properties
Longa's Landau de Gennes theory
Molecular structure
Molecular theory
nematic liquid crystals
Order parameters
Tensors
twist-bend phase
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Summary:We present a critical analysis of the existing phenomenological theories of the nematic twist-bend phase including the models proposed by Dozov and Selinger and the more general Landau de Gennes theory of L. Longa and W. Tomczyk. The role of the flexoelectric polarisation is considered in detail as well as the stabilisation of the nanoscale helical structure of the twist-bend phase. In particular we focus into the mechanism of the reduction of the bend elastic constant determined by negative flexoelectric corrections and discuss why the splay elastic constant is not reduced at all. A molecular theory of elasticity of bent-core nematics, which also enables one to describe the reduction of the bend elastic constant, is considered in detail as well. Finally we consider two different tensor orientational order parameters of the twist-bend phase which describe all kinds of uniaxial and local biaxial ordering of bent-core molecules in the twist-bend phase.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678292.2024.2321464