Dynamic Response of Glassy Dispersions in a Nematic Liquid Crystal

TL;DR

This study investigates the dynamic behavior of glassy dispersions in nematic liquid crystals, revealing how nematic elasticity influences flow and identifying a critical frequency related to material properties.

Contribution

First systematic measurement of the dynamic response of glassy dispersions in nematic liquid crystals, with a theoretical model linking elasticity and viscous behavior.

Findings

Nematic elasticity dominates at low frequencies, preventing flow.

A critical frequency $$ is identified where viscous response changes.

The loss tangent $ an\delta$ is independent of colloid volume fraction.

Abstract

We present the first systematic measurements of the dynamic response of a glassy soft-solid formed on dispersing colloids in a thermotropic nematic liquid crystal. Through applying a simple theoretical model, we reveal that the nematic elasticity dominates at low frequencies (longest timescales) and prevents flow. The Ericksen number $E_R$, determines a critical frequency $\omega_c$, above which the viscous component $G'' \propto \omega ^{1/2}$. We find that the value of tan$\delta$ is independent of the colloidal volume fraction ($\phi$), and is determined by the ratio of lengthscales associated with the defect-line density and the size of colloid-free nematic regions trapped within the composite.