Pattern formation from consistent dynamical closures of uniaxial nematic liquid crystals

TL;DR

This paper investigates pattern formation in uniaxial nematic liquid crystals using dynamic closure approximations within a mesoscopic thermodynamics framework, revealing spontaneous pattern and wave generation without external forces.

Contribution

It introduces a novel free-energy expression based on a dynamic closure approximation and analyzes pattern formation in lyotropic nematics without external driving.

Findings

Patterns and traveling waves can form spontaneously in lyotropic nematics.

A new free-energy expression is derived from the fourth order orientational parameter.

Dynamic closure approximations predict phase coexistence and pattern formation.

Abstract

Pattern formation in uniaxial polymeric liquid crystals is studied for different dynamic closure approximations. Using the principles of mesoscopic non-equilibrium thermodynamics in a mean-field approach, we derive a Fokker-Planck equation for the single-particle non-homogeneous distribution function of particle orientations and the evolution equations for the second and fourth order orientational tensor parameters. Afterwards, two dynamic closure approximations are discussed, one of them considering the relaxation of the fourth order orientational parameter and leading to a novel expression for the free-energy like function in terms of the scalar order parameter. Considering the evolution equation of the density of the system and values of the interaction parameter for which isotropic and nematic phases coexist, our analysis predicts that patterns and traveling waves can be produced in lyotropic uniaxial nematics even in the absence of external driving.