An anchoring transition at surfaces with grafted liquid-crystalline chain molecules

TL;DR

This paper investigates how grafted liquid crystalline chains influence nematic liquid crystal alignment at surfaces, revealing a second order transition from tilted to perpendicular anchoring driven by grafting density.

Contribution

It introduces a combined simulation and mean field approach to understand surface anchoring transitions caused by grafted liquid crystalline chains.

Findings

Swollen tilted chain layers can induce perpendicular nematic alignment.

A second order transition from tilted to homeotropic anchoring is predicted.

The transition is controlled by grafting density and interface structure.

Abstract

The anchoring of nematic liquid crystals on surfaces with grafted liquid crystalline chain molecules is studied by computer simulations and within a mean field approach. The computer simulations show that a swollen layer of collectively tilted chains may induce untilted homeotropic (perpendicular) alignment in the nematic fluid. The results can be understood within a simple theoretical model. The anchoring on a layer of mutually attractive chains is determined by the structure of the interface between the layer of chain molecules and the solvent. It is controlled by an interplay between the attractive chain interactions, the translational entropy of the solvent and its elasticity. A second order anchoring transition driven by the grafting density from tilted to homeotropic alignment is predicted.