Ferroelectric ordering in chiral smectic- C* liquid crystals determined by nonchiral intermolecular interactions

Osipov, M.A. and Gorkunov, M.V. (2008) Ferroelectric ordering in chiral smectic- C* liquid crystals determined by nonchiral intermolecular interactions. Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 77 (3). 031701/1-031701/13. ISSN 1063-651X

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Abstract

General microscopic mechanism of ferroelectric ordering in chiral smectic-C* liquid crystals is considered. It is shown that if the mesogenic molecules have a sufficiently low symmetry, the spontaneous polarization is proportional to one of the biaxial vector order parameters of the smectic-C phase. This order parameter may be determined by intermolecular interactions which are not sensitive to molecular chirality. At the same time, the polarization is also proportional to a pseudoscalar parameter which vanishes if the molecules are nonchiral. The general statistical theory of ferroelectric ordering is illustrated by two particular models. The first model is based on electrostatic quadrupole-quadrupole interactions, and it enables one to obtain explicit analytical expressions for the spontaneous polarization. In the second model, the molecular chirality and polarity are determined by a pair of off-center nonparallel dipoles. For this case, the spontaneous polarization is calculated numerically as a function of temperature. The theory provides a more general interpretation of the previous approaches including the classical Boulder model.

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