Molecular field theory for polar, biaxial bent-core nematics

We have studied a polar, biaxial nematic liquid crystal formed from bent-core molecules using molecular field theory. The model includes a simple Heisenberg-form dipolar intermolecular interaction in addition to the usual quadrupolar nematic interaction, and mimics a system consisting of nematogenic...

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Bibliographic Details
Published in:Liquid crystals 2016-08, Vol.43 (10), p.1448-1461
Main Authors: To, T. B. T., Sluckin, T. J., Luckhurst, G. R.
Format: Article
Language:English
Subjects:
Alignment
bent-core nematics
Biaxial nematics
Crystals
Dipoles
Field theory
Liquid crystals
Magnetic fields
Mathematical models
Molecular chemistry
molecular field theory
Nematic
Nematic crystals
Phase transformations
Phase transitions
polar nematics
V-shaped molecules
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Summary:We have studied a polar, biaxial nematic liquid crystal formed from bent-core molecules using molecular field theory. The model includes a simple Heisenberg-form dipolar intermolecular interaction in addition to the usual quadrupolar nematic interaction, and mimics a system consisting of nematogenic bent-core molecules with a large transverse dipole along the bisector of the two molecular arms. Such systems are regarded as good candidates for biaxial nematic liquid crystals. In principle, the molecular dipoles can align, thus stabilising the ordering of the minor axes. Our calculations predict that, for suitable values of the bent-core interarm angle, the biaxial nematic phase can be stabilised at higher temperatures than in the absence of the transverse dipole. In general, the transverse macroscopic polar order stabilises the biaxial nematic phase. In particular, for a large enough dipolar interaction, the Landau point in the pure biaxial nematic develops into a line of first-order polar biaxial nematic-to-isotropic phase transitions.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678292.2016.1181214