title: Collective intermolecular motions dominate the picosecond dynamics of short polymer chains.
abstract: Neutron scattering and extensive molecular dynamics simulations of an all atom C(100)H(202) system were performed to address the short-time dynamics leading to center-of-mass self-diffusion. The simulated dynamics are in excellent agreement with resolution resolved time-of-flight quasielastic neutron scattering. The anomalous subdiffusive center-of-mass motion could be modeled by explicitly accounting for viscoelastic hydrodynamic interactions. A model-free analysis of the local reorientations of the molecular backbone revealed three relaxation processes: While two relaxations characterize local bond rotation and global molecular reorientation, the third component on intermediate times could be attributed to transient flowlike motions of atoms on different molecules. The existence of these collective motions, which are clearly visualized in this Letter, strongly contribute to the chain relaxations in molecular liquids.
authors.affiliation: Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) and Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, 85747 Garching, Germany and Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Kristallographie und Strukturphysik, Staudtstrasse 3, 91058 Erlangen, Germany.
authors.forename: Humphrey
authors.initials: H
authors.lastname: Morhenn
authors.forename: Sebastian
authors.initials: S
authors.lastname: Busch
authors.forename: Hendrik
authors.initials: H
authors.lastname: Meyer
authors.forename: Dieter
authors.initials: D
authors.lastname: Richter
authors.forename: Winfried
authors.initials: W
authors.lastname: Petry
authors.forename: Tobias
authors.initials: T
authors.lastname: Unruh
mesh_terms: D003198:Computer Simulation; D004548:Elasticity; D057446:Hydrodynamics; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D033363:Neutron Diffraction; D020959:Polyethylene / Q000737:chemistry*; D014783:Viscosity
chemical_list: D020959:Polyethylene