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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 23: Polymer Dynamics

CPP 23.3: Vortrag

Mittwoch, 13. März 2013, 10:15–10:30, H39

Local, global and collective dynamics in a short polymer system. — •Humphrey Morhenn^1,2, Sebastian Busch³, and Tobias Unruh² — ¹Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) and Lehrstuhl für Funktionale Materialien, Technische Universität München, Germany — ²Lehrstuhl für Kristallographie und Strukturphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany — ³Department of Biochemistry, University of Oxford, United Kingdom

The n-alkane C₁₀₀H₂₀₂ is an oligomer on the edge of being a polymer. Although its chains are shorter than the entanglement length and long enough to show Gaussian chain statistics, the Rouse model fails to predict the chain dynamics. Detailed quasielastic neutron scattering experiments and extensive molecular dynamics simulations were performed, providing complementary pictures on the molecular motions. Three distinct relaxation processes on the pico- to nanosecond time regime were separated, eventually leading to molecular self-diffusion. Two relaxations were found to correspond to local torsional and global rotational motions of single molecules, whereas a third, intermediate relaxation can be explained by intermolecular collective motions. Taking these contributions into account a physical model describing molecular self-diffusion is being developed.