Structure formation in monolayers composed of hard bent-core molecules

TL;DR

This study uses density functional theory and Monte Carlo simulations to explore how molecular shape influences the formation of various liquid crystalline structures in monolayers of bent-core molecules, revealing sensitivity to shape details and the potential stability of nematic splay-bend phases.

Contribution

It provides a theoretical analysis of how molecular features affect structure stability in bent-core liquid crystal monolayers, highlighting the role of excluded-volume interactions and shape parameters.

Findings

Lamellar antiferroelectric phases dominate for simple shapes.

Structure stability is highly sensitive to molecular shape details.

A stable nematic splay-bend phase exists for large opening angles and moderate thickness.

Abstract

Two-dimensional ensembles of bent-core shaped molecules attain at highly orienting surfaces liquid crystalline structures characteristic mostly for lamellar chiral or nonchiral antiferroelectric order. Here, using the Onsager-type of density functional theory supplemented by constant-pressure Monte-Carlo (MC) simulation we investigate the role of excluded-volume interactions in stabilizing different structures in monolayers filled with bent-shaped molecules. We study influence of molecular features, like the apex angle, thickness of the arm and the type of the arm edges on the stability of layered structures. For simple molecular shapes taken the observed phases are dominated by the lamellar antiferroelectric type as observed experimentally, but a considerable sensitivity of the ordering to details of the molecular shape is found for order parameters and wave vectors of the structures. Interestingly, for large opening angles and not too thick molecules a window of stable nematic splay-bend phase is shown to exist. The presented theory models equilibrium properties of bent-core liquid crystals subjected to strong planar anchoring, in the case when details of the surface are of secondary importance.