Investigation of NLC Director Orientational Deformations in Electric Field for Different Boundary Conditions

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Abstract
The work investigates certain director orientational deformations and the corresponding NLC optical characteristics in electric field for different boundary conditions and consists of two Parts. In Part I we study the effect of Total Internal Reflection (TIR) in NLC layer with homeotropic ( B -effect) or planar ( S-effect) initial orientation subjected to an external electric field. Strong anchoring of the NLC molecules with the substrates is assumed. The intensity of the transmitted light vs angle of incidence is shown to exhibit very sharp and deep oscillations in the vicinity of the TIR angle, the period and the amplitude of the oscillations depending on the applied voltage. The calculated TIR values in B- and S-effects agree with our experimental data. In Part II we investigate orientational deformations of homeotropically aligned NLC layer in an electric field parallel and perpendicular to the initial director orientation ( B-effect and flexoeffect respectively). The apparent strong anchoring of the NLC molecules with the substrates in B-effect, found in our experiment, is explained by introducing the surface energy coupling in the new form.