Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: POSTERS Driven Soft Matter
CPP 20.2: Poster
Wednesday, February 27, 2008, 16:00–18:30, Poster A
Bistable and chaotic solutions in polar nano-rod systems under shear — •Stefan Grandner1, Sebastian Heidenreich2, Siegfried Hess2, and Sabine H. L. Klapp1,2 — 1Stranski-Laboratorium, TU Berlin, Straße des 17. Juni 115, D-10623 Berlin, Germany — 2Institut für theoretische Physik, TU Berlin, Hardenbergstraße 36, D-10623 Berlin, Germany
The orientational dynamics of rod-like particles with permanent dipole moment shows a time dependent response in a plane Couette flow. This behavior can be described by nonlinear mesoscopic relaxation equations for the alignment tensor [1] and the polarization [2] combined with a generalized Landau free energy. This yields an eight-dimensional coupled system of differential equations. For simplicity we assume a spatially homogeneous system. Numerical results are presented for longitudinal dipoles where the equilibrium state is a polarized nematic. The large variety of periodic, transient chaotic and chaotic states is summarized in solution diagrams [3]. Compared to the non-polar case we observe a preference of dynamic states out of the shear plane and a higher sensitivity to initial conditions, resulting in larger bistability regions. The time dependence of the electric polarization generates magnetic fields of measurable strength.
[1] S. Hess, Z. Naturforsch. 30a, 728, 1224 (1975).
[2] S. Grandner, S. Heidenreich, P. Ilg, S. H. L. Klapp, and S. Hess, Phys. Rev. E 75, 040701(R) (2007).
[3] S. Grandner, S. Heidenreich, S. Hess, and S. H. L. Klapp - Polar nano-rods under shear: From equilibrium to chaos (submitted).