title: Polar nano-rods under shear: from equilibrium to chaos.
abstract: The orientational dynamics of rod-like particles with permanent (electric or magnetic) dipole moments in a plane Couette shear flow is investigated using mesoscopic relaxation equations combined with a generalized Landau free energy. The free energy contribution due to the coupling between average alignment and dipole orientation is derived on a microscopic basis. Numerical results of the resulting eight-dimensional dynamical system are presented for the case of longitudinal dipoles and thermodynamic conditions where the equilibrium state is a (polar or non-polar) nematic. Solution diagrams reveal presence of a large variety of periodic, transient chaotic, and chaotic dynamic states of the average alignment and dipole moment, respectively, appearing as a function of Deborah number and tumbling parameter. Compared to rods without dipoles we observe a significant preference of out-of-plane kayaking-tumbling states and, generally, a higher sensitivity to the initial conditions including bistability. We also demonstrate that the average (electric) dipole moment characterizing most of the observed states yields electrodynamic (magnetic) fields of measurable strength.
authors.affiliation: Institut für Theoretische Physik, Sekr. PN 7-1, Technische Universität Berlin, Hardenbergstrasse 36, D-10623, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Grandner
authors.forename: S
authors.initials: S
authors.lastname: Heidenreich
authors.forename: S
authors.initials: S
authors.lastname: Hess
authors.forename: S H L
authors.initials: SH
authors.lastname: Klapp
mesh_terms: D003198:Computer Simulation; D004574:Electromagnetic Fields; D008956:Models, Chemical; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry* / Q000528:radiation effects* / Q000648:ultrastructure; D017711:Nonlinear Dynamics; D011829:Radiation Dosage; D033081:Shear Strength; D055672:Static Electricity