Long-time relaxation dynamics in nematic and smectic liquid crystals of soft-repulsive colloidal rods

TL;DR

This study investigates how long-range ordering in nematic and smectic liquid-crystalline phases of soft-repulsive colloidal rods affects their relaxation and diffusion dynamics, revealing temperature-dependent behaviors and heterogeneous diffusion patterns.

Contribution

It provides new insights into the influence of translational and orientational order on colloidal rod dynamics using Dynamic Monte Carlo simulations across different phases and temperatures.

Findings

Long-range order impacts diffusion anisotropy.

Temperature controls relaxation times and self-diffusion coefficients.

Presence of fast-diffusing rods modulated by temperature.

Abstract

Understanding the relaxation dynamics of colloidal suspensions is crucial to identify the elements that influence the mobility of their constituents, assess their macroscopic response across the relevant time and length scales, and thus disclose the fundamentals underpinning their exploitation in formulation engineering. In this work, we specifically assess the impact of long-ranged ordering on the relaxation dynamics of suspensions of soft-repulsive rod-like particles, which are able to self-organise into nematic and smectic liquid-crystalline phases. By performing Dynamic Monte Carlo simulations, we analyse the effect of translational and orientational order on the diffusion of the rods along the relevant directions imposed by the morphology of the background phases. To provide a clear picture of the resulting dynamics, we assess their dependence on temperature, which can dramatically determine the response time of the system relaxation and the self-diffusion coefficients of the rods. The computation of the van Hove correlation functions allows us to identify the existence of rods that diffuse significantly faster than the average and whose concentration can be accurately adjusted by a suitable choice of temperature.