Alignment transition in a nematic liquid crystal due to field-induced breaking of anchoring

TL;DR

This paper investigates how an electric field can induce a transition in nematic liquid crystal alignment from homeotropic to quasi-planar by breaking surface anchoring, revealing metastable states and the influence of cell thickness.

Contribution

It demonstrates field-induced anchoring breaking in nematic liquid crystals and characterizes the resulting alignment transition and metastable states.

Findings

DSM2 state breaks surface coupling and causes metastable quasi-planar alignment

Transition threshold depends on cell thickness

Field application leads to turbulent states affecting anchoring

Abstract

We report on the alignment transition of a nematic liquid crystal from initially homeotropic to quasi-planar due to field-induced anchoring breaking. The initial homeotropic alignment is achieved by Langmuir-Blodgett monolayers. In this geometry the anchoring strength can be evaluated by the Frederiks transition technique. Applying an electric field above a certain threshold provokes turbulent states denoted DSM1 and DSM2. While DSM1 does not affect the anchoring, DSM2 breaks the coupling between the surface and the liquid crystal: switching off the field from a DSM2 state does not immediately restore the homeotropic alignment. Instead, we obtain a quasi-planar metastable alignment. The cell thickness dependence for the transition is related to the