Biaxiality-induced magnetic field effects in bent-core nematics: molecular-field and Landau theory.
Nematic liquid crystals composed of bent-core molecules exhibit unusual properties, including an enhanced Cotton-Mouton effect and an increasing isotropic (paranematic)-nematic phase transition temperature as a function of magnetic field. These systems are thought to be good candidate biaxial liquid crystals. Prompted by these experiments, we investigate theoretically the effect of molecular biaxiality on magnetic-field-induced phenomena for nematic liquid crystals, using both molecular field and Landau theory. The geometric mean approximation is used in order to specify the degree of molecular biaxiality using a single parameter. We reproduce experimental field-induced phenomena and predict also an experimentally accessible magnetic critical point. The Cotton-Mouton effect and temperature dependence of the paranematic-nematic phase transition are more pronounced with increased molecular biaxiality. We compare our theoretical approaches and make contact with recent relevant experimental results on bent-core molecular systems.
School of Mathematics, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
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School of Mathematics, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
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Sluckin
School of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
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Luckhurst