Landau theory-based estimates for viscosity coefficients of uniaxial and biaxial nematic liquid crystals

TL;DR

This paper uses Landau theory to relate viscosity coefficients of uniaxial and biaxial nematic liquid crystals to their order parameters, enabling potential experimental determination of phenomenological parameters.

Contribution

It establishes a theoretical framework linking viscosity coefficients to macroscopic order parameters in nematic liquid crystals, allowing parameter estimation from experimental data.

Findings

Eight phenomenological parameters are needed for biaxial nematics.

Viscosity coefficients depend on uniaxial and biaxial order parameters.

Possible to determine all parameters from temperature-dependent viscosity measurements.

Abstract

Using Landau theory, it is shown that eight phenomenological parameters are needed to describe and distinguish the twelve viscosity coefficients of a biaxial nematic phase, or the five viscosity coefficients of a uniaxial nematic phase. The dependence of the coefficients on the macroscopic uniaxial and biaxial order parameters is established. Since these order parameters are determined by the anisotropies of the dielectric constant, we show that it should be possible to determine values for all eight of the phenomenological parameters of the theory from measurements of the temperature dependence of the five viscosities of a uniaxial phase.