Formation of disclination lines near a free nematic interface

TL;DR

This study investigates the formation and behavior of -1/2 wedge disclination lines near free surfaces in nematic liquid crystals, linking their position to material parameters and observing their collapse due to temperature effects.

Contribution

It introduces a combined planar and three-dimensional modeling approach to relate disclination line positions to material properties and observes temperature-induced disclination collapse.

Findings

Disclination line position depends on elastic constants and anchoring energy.

Temperature-induced anchoring angle transition causes disclination collapse.

No real disclination line exists near the nematic/isotropic front in growth experiments.

Abstract

We have studied the nucleation and the physical properties of a -1/2 wedge disclination line near the free surface of a confined nematic liquid crystal. The position of the disclination line has been related to the material parameters (elastic constants, anchoring energy and favored anchoring angle of the molecules at the free surface). The use of a planar model for the structure of the director field (whose predictions have been contrasted to those of a fully three-dimensional model) has allowed us to relate the experimentally observed position of the disclination line to the relevant properties of the liquid crystals. In particular, we have been able to observe the collapse of the disclination line due to a temperature-induced anchoring angle transition, which has allowed us to rule out the presence of a real disclination line near the nematic/isotropic front in directional growth experiments. 61.30.Jf,61.30.Gd