Description: Cooperative dynamics in homopolymer melts: a comparision of theoretical predictions with neutron spin echo experiments

This title appears in the Scientific Report : 2008

Cooperative dynamics in homopolymer melts: a comparision of theoretical predictions with neutron spin echo experiments

We present a comparison between theoretical predictions of the generalized Langevin equation for cooperative dynamics (CDGLE) and neutron spin echo data of dynamic structure factors for polyethylene melts. Experiments cover an extended range of length and time scales, providing a compelling test for...

Personal Name(s):	Zamponi, M.
	Wischnewski, A. / Monkenbusch, M. / Willner, L. / Richter, D. / Falus, P. / Farago, B. / Guenza, M.G.
Contributing Institute:	JCNS; JCNS Streumethoden; IFF-4 Neutronenstreuung; IFF-5
Published in:	The @journal of physical chemistry / B, 112 (2008) S. 16220 - 16229
Imprint:	Washington, DC Soc. 2008
Physical Description:	16220 - 16229
PubMed ID:	19072142
DOI:	10.1021/jp807035z
Document Type:	Journal Article
Research Program:	Großgeräte für die Forschung mit Photonen, Neutronen und Ionen (PNI) Kondensierte Materie
Series Title:	Journal of Physical Chemistry B 112
Subject (ZB):	J
	Publikationsportal JuSER

Please use the identifier: http://dx.doi.org/10.1021/jp807035z in citations.

We present a comparison between theoretical predictions of the generalized Langevin equation for cooperative dynamics (CDGLE) and neutron spin echo data of dynamic structure factors for polyethylene melts. Experiments cover an extended range of length and time scales, providing a compelling test for the theoretical approach. Samples investigated include chains with increasing molecular weights undergoing dynamics across the unentangled to entangled transition. Measured center-of-mass (com) mean-square displacements display a crossover from subdiffusive to diffusive dynamics. The generalized Langevin equation for cooperative dynamics relates this anomalous diffusion to the presence of the interpolymer potential, which correlates the dynamics of a group of slowly diffusing molecules in a dynamically heterogeneous liquid. Theoretical predictions of the subdiffusive behavior, of its crossover to free diffusion, and of the number of macromolecules undergoing cooperative motion are in quantitative agreement with experiments.