Modeling planar degenerate wetting and anchoring in nematic liquid crystals

TL;DR

This paper introduces a simple surface potential model for planar degenerate anchoring in nematic liquid crystals, analyzing its effects on wetting and anchoring properties across different phases with experimental validation.

Contribution

It develops a minimal tensorial Landau-de Gennes model including fourth-order terms to accurately describe degenerate planar anchoring and wetting phenomena in nematic liquid crystals.

Findings

Successful modeling of degenerate planar anchoring with positive scalar order-parameter.

Wetting layer exhibits uniaxial ordering with negative scalar order-parameter in the isotropic phase.

Large anchoring strength induces a transition to the planar degenerate state.

Abstract

We propose a simple surface potential favoring the planar degenerate anchoring of nematic liquid crystals, i.e., the tendency of the molecules to align parallel to one another along any direction parallel to the surface. We show that, at lowest order in the tensorial Landau-de Gennes order-parameter, fourth-order terms must be included. We analyze the anchoring and wetting properties of this surface potential. In the nematic phase, we find the desired degenerate planar anchoring, with positive scalar order-parameter and some surface biaxiality. In the isotropic phase, we find, in agreement with experiments, that the wetting layer may exhibit a uniaxial ordering with negative scalar order-parameter. For large enough anchoring strength, this negative ordering transits towards the planar degenerate state.