Field-induced director dynamics in confined nematic liquid crystals imposed by a strong orthogonal electric field

Abstract

The field-induced director dynamics for a low molar mass nematic liquid crystal (LC) has been investigated theoretically based on the hydrodynamic theory including the director motion with appropriate boundary and initial conditions. Analysis of the numerical results for the turn-on process provides evidence for the appearance of the spatially periodic patterns in 4-n-pentyl-4'-cyanobiphenyl LC film, only in response to the suddenly applied strong electric field orthogonal to the magnetic field. It has been shown that at the values of the voltage of 200 V across the 194.7 μm LC film and the magnetic field of 7.05 T directed at the angle α=1.57(~89.99°) between two fields, there is a threshold value of the amplitude of the thermal fluctuations of the director over the LC sample which provides the nonuniform rotation mode rather than the uniform one, whereas the lower values both of the amplitude and the angle α [<1.565(~88.81°)] dominate the uniform mode. During the turn-off process, the reorientation of the director to its equilibrium orientation is characterized by the complex destruction of the initially periodic structure to a monodomain state.