Distinct temperature-dependent anchoring behavior in liquid crystals triggered by interfacial local organizations

Abstract

Anchoring phenomena at surfaces/interfaces have been receiving tremendous attention due to scientific interests in their multifariousness and complexity, as well as the desire to control itself for application even beyond liquid crystal (LC) display. From a common perspective, nematic LCs (NLCs) anchor more strongly to surfaces upon lowering temperature, mainly due to the stiffened endogenous order parameter and the enhanced NLC-surface interactions. Here, we explore an unconventional anchoring behavior of a NLC with negative dielectric anisotropy on a perfluoro-polymer surface. It was found that the polar anchoring coefficient (W) of planar orientational state decreases with decreasing temperature. When reaching a critical temperature at which W becomes nearly zero, the bulk orientation changes from planar to vertical orientational state discontinuously. We show that this behavior is mediated by surface-enhanced smectic wetting structures from both experimental and theoretical approaches.