Freedericksz's transition in nematics layer: threshold conditions and stationary states

Marek Andrzej Kojdecki

doi:10.1117/12.156940

15 October 1993 Freedericksz's transition in nematics layer: threshold conditions and stationary states

Marek Andrzej Kojdecki

Proceedings Volume 1845, Liquid and Solid State Crystals: Physics, Technology and Applications; (1993) https://doi.org/10.1117/12.156940
Event: Liquid and Solid State Crystals: Physics, Technology, and Applications, 1992, Zakopane, Poland

Abstract

Freedericksz' transition in twisted nematics layer, in which all characteristic properties of nematic liquid crystal manifest, is one of the most important phenomena observed in these media. It may be understood as a transition (forward and backward) between two stationary states, one of them induced by boundary conditions on layer surfaces and the other induced by those boundary conditions and constant external field (either magnetic or electric) applied to the layer. In this paper the study of stationary states in twisted nematics layer is presented. The considerations are based on Ericksen's and Leslie's macroscopic theory of incompressible nematics, which seems to enable obtaining sufficiently exact and relatively simple description of the phenomenon. The full system of equations of motion of nematics layer (in one- dimensional approximation) has been derived from the Leslie's equations. The stability of stationary states in electric field has been investigated. New stability condition for stationary states has been deduced from a linearized version of these equations; it implies the existence of two types of stationary states in the layer, induced by the boundary conditions: with nematics molecules parallel or nonparallel to the surfaces. The threshold magnitudes of the total twist angle of the layer and of the constant voltage applied to the layer have been estimated. The usefulness of the formulae for threshold magnitudes has been confirmed by the results of computations of stationary states in quasi-MBBA (MBBA of assumed positive dielectric anisotropy), which are presented in the paper.

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Marek Andrzej Kojdecki "Freedericksz's transition in nematics layer: threshold conditions and stationary states", Proc. SPIE 1845, Liquid and Solid State Crystals: Physics, Technology and Applications, (15 October 1993); https://doi.org/10.1117/12.156940

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KEYWORDS

Information operations

Lithium

Ions

Liquid crystals

Anisotropy

Crystals

Dielectrics

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