Thermal phase diagrams of columnar liquid crystals

TL;DR

This paper investigates the thermal phase transitions in columnar liquid crystals, specifically HHTT, using a 3D model with octupolar interactions, revealing how temperature influences the emergence of ordered and helical phases.

Contribution

It introduces a combined mean-field and Monte Carlo approach to map the phase diagram of a model for columnar liquid crystals with octupolar interactions.

Findings

Columns order with linear polarization at intermediate temperatures.

Helical phases develop at lower temperatures due to frustration.

Similar results from mean-field and Monte Carlo methods.

Abstract

In order to understand the possible sequence of transitions from the disordered columnar phase to the helical phase in hexa(hexylthio)triphenylene (HHTT), we study a three-dimensional planar model with octupolar interactions inscribed on a triangular lattice of columns. We obtain thermal phase diagrams using a mean-field approximation and Monte Carlo simulations. These two approaches give similar results, namely, in the quasi one-dimensional regime, as the temperature is lowered, the columns order with a linear polarization, whereas helical phases develop at lower temperatures. The helicity patterns of the helical phases are determined by the exact nature of the frustration in the system, itself related to the octupolar nature of the molecules.