Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Polymer Dynamics
CPP 33.3: Vortrag
Donnerstag, 29. März 2012, 10:15–10:30, C 264
Viscoelastic hydrodynamic interactions explain anomalous CM diffusion in polymer melts — •Hendrik Meyer, Jean Farago, and A.N. Semenov — Institut Charles Sadron, CNRS, 67034 Strasbourg, France
Contrary to common belief, hydrodynamic interactions in polymer melts are not screened beyond the monomer length and are important in transient regimes. We show that viscoelastic hydrodynamic interactions (VHI) lead to anomalous dynamics of a tagged chain in an unentangled melt at t<tN, the Rouse time. The center-of-mass (CM) mean-square displacement is enhanced by a large factor increasing with chain length. We develop a theory of VHI-controlled chain dynamics yielding a negative CM velocity autocorrelation function which agrees with our molecular dynamics simulations without any fitting parameter. It is shown that Langevin friction strongly affects the short-t CM dynamics, also captured by our theory. All results apply also to entangled melts for times shorter than the entanglement time. Transient VHI effects thus provide the dominant contribution to the subdiffusive CM motion universally observed in simulations and experiments. [Phys. Rev. Lett. 107, 178301 (2011)]