Dynamics of supramolecular structures induced in liquid crystals

Abstract

A theory is experimentally validated for the first time, which describes (within nonequilibrium hydrodynamics) the properties of supramolecular spatially periodic structures in a planar layer of a cholesteric liquid crystal at ultrasound intensities exceeding the threshold of their formation in a frequency range where the wavelength is larger than the cholesteric helix pitch. Distortions in the layer texture in planar and wedgeshaped capillaries with planar boundary conditions at normal incidence of longitudinal waves have been observed for the frequency range of 1–4 MHz. The domain periods at the threshold of the effect and above it are determined for layers 20–100 μm thick at helix pitch values of 2–10 μm. The dependences of the domain period on the ultrasound intensity and the preliminary layer extension have been established. A model constructed with allowance for structural relaxation processes and nonlinear relaxation phenomena is tested. It is shown that a complete description of the effect, which is consistent with the experimental data, can be obtained only using approach.