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DY: Fachverband Dynamik und Statistische Physik

DY 10: Brownian motion and transport I

DY 10.1: Hauptvortrag

Dienstag, 24. März 2009, 14:00–14:30, HÜL 386

Self-Dynamics of a Slender Rod — •Thomas Franosch — Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, D-80333 München, Germany

Rods of high aspect ratio in concentrated suspensions constitute strongly interacting systems with rich dynamics: transport slows down drastically and the anisotropy of the motion becomes arbitrarily large. A general theory for the anisotropic motion of rods in entangled suspensions is a long-standing problem, due to the intricacy of the many-body interaction. We have performed extensive computer simulations for a model system consisting of single needle exploring a disordered planar array of obstacles. For ballistic needles we find an enhancement of diffusion as the density of obstacles increases which may be explained by heuristic scaling argument.

For Brownian needles we measure the intermediate scattering function and find a peculiar power-law decay in the highly entangled regime. This behavior can be explained from the strong coupling of translational and rotational motion within a tube and. We then develop a mesoscopic description of the dynamics down to the length scale of the interparticle distance. Our theory is based on the exact solution of the Smoluchowski-Perrin equation for the unconstrained motion. Employing the measured diffusion coefficients as input parameters we find quantitative agreement with our Brownian dynamics simulations in the dense regime