Liquid relaxation: A new Parodi-like relation for nematic liquid crystals

TL;DR

This paper introduces a hydrodynamic theory for nematic liquid crystals that extends classical models by predicting a new relation among Leslie viscosities, validated through experiments, simulations, and theory.

Contribution

It proposes a novel Parodi-like relation involving five viscosities, expanding understanding of liquid crystal dynamics beyond classical theories.

Findings

Reproduces Ericksen-Leslie theory in low-frequency limit

Predicts a new nonlinear relation among Leslie viscosities

Validated against experiments, simulations, and theoretical predictions

Abstract

We put forward a hydrodynamic theory of nematic liquid crystals that includes both anisotropic elasticity and dynamic relaxation. Liquid remodeling is encompassed through a continuous update of the shear-stress free configuration. The low-frequency limit of the dynamical theory reproduces the classical Ericksen-Leslie theory, but it predicts two independent identities between the six Leslie viscosity coefficients. One replicates Parodi's relation, while the other-which involves five Leslie viscosities in a nonlinear way-is new. We discuss its significance, and we test its validity against evidence from physical experiments, independent theoretical predictions, and molecular-dynamics simulations.