The effect of a modified surface anchoring potential on the cholesteric–nematic transition

Abstract

As it is known, the Rapini-Papoular potential is suitable for description of anchoring energy between the liquid crystal and bounding surfaces in the case of small deviations of the director from the easy orientation axis. We use modified surface potential that can describe the anchoring energy at large deviations of the director more adequately. The interaction effect of a cholesteric liquid crystal with a bounding surfaces on the nature and features of cholesteric-nematic phase transitions induced by an external magnetic field is studied. We determine the conditions for existence of three different phases in a cholesteric liquid crystal layer with a finite homeotropic anchoring at the boundaries. The dependencies of the threshold fields of orientational transitions between the phases of a liquid crystal on the material parameters of the cell are calculated. Landau expansions of the total free energy of cholesteric near the transition points are constructed. We determine the tricritical values of the anisotropy parameter of the surface anchoring, which characterize the nature of transitions between the phases of a cholesteric liquid crystal.