Investigation of anchoring effects in ferroelectric liquid crystals

Abstract

Electrically suppressed ferroelectric liquid crystal mode is observed when the long molecular axes within the helical structure are uniformly distributed and cell thickness is greater than the helix pitch, i.e., the helix is not suppressed by the bounding surfaces. The role of the anchoring energy, caused by the aligning surfaces is to orient the helical axis without any suppression of the helix cone. These conditions make the balance between surface anchoring interactions and elastic energy highly important in the electro-optical properties of the cell. Hence, a trade-off between the helix pitch and the liquid crystal layer thickness is crucial for the alignment quality. In this study we deal with the electric field free steady-state two-domain twisted helical structure. Our hypothesis in this article is that the domain structures are explained by the effect of polar interactions between the ferroelectric liquid crystal molecules and the surface. Consideration of this term leads to the decrease of the free energy when the contribution from polar interactions increases. Theoretical investigation of the helix unwinding versus liquid crystal thickness shows that the polar interactions promote formation of uniform structures. This investigation is significant in understanding the fundamentals of optical effects, occurring in electrically suppressed ferroelectric liquid crystal mode.