Oscillatory motion of sheared nanorods beyond the nematic phase

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.