Oscillatory motion of sheared nanorods beyond the nematic phase

TL;DR

This paper investigates the dynamic oscillatory behavior of nanorods under shear flow, revealing oscillations beyond the nematic phase through bifurcation analysis of tensorial order parameters.

Contribution

It introduces a systematic bifurcation analysis of mesoscopic equations for nanorod orientation, uncovering oscillatory states in isotropic conditions not previously reported.

Findings

Oscillatory states with wagging motion exist beyond the nematic phase.

Oscillations occur at small tumbling parameters.

Full phase diagrams map concentration and shear rate effects.

Abstract

We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial orientational order parameter. We investigating these equations via a systematic bifurcation analysis based on a numerical continuation technique, focusing on spatially homogeneous states. Exploring a wide range of parameters we find, unexpectedly, that states with oscillatory motion can exist even under conditions where the equilibrium system is isotropic. These oscillatory states are characterized by wagging motion of the paranematic director, and they occur if the tumbling parameter is sufficiently small. We also present full non-equilibrium phase diagrams, in the plane spanned by the concentration and the shear rate.