Coarse-grained surface energies and temperature-induced anchoring transitions in nematic liquid crystals

TL;DR

This paper develops a coarse-grained model for surface energies in nematic liquid crystals, explaining temperature-dependent anchoring transitions and the smoothing of surface potential angular dependence.

Contribution

It introduces a temperature-dependent renormalization approach for surface energy, explaining anchoring transitions and the effectiveness of the Rapini-Papoular form.

Findings

Quantitative description of temperature dependence of anchoring energy

Explanation of temperature-induced anchoring transitions

Smoothing of the surface potential angular dependence

Abstract

We introduce a coarse-grained description of the surface energy of a nematic liquid crystal. The thermal fluctuations of the nematic director close to the surface renormalize at macroscopic scales the bare surface potential in a temperature-dependent way. The angular dependence of the renormalized potential is dramatically smoothed, thus explaining the success of the Rapini-Papoular form. Close to the isotropic phase, the anchoring energy is strongly suppressed and the change of its shape allows for anchoring transitions. Our theory describes quantitatively the temperature dependence of the anchoring energy and the temperature-induced anchoring transitions reported in the literature.