Europhys. Lett.
Volume 72, Number 6, December 2005
Page(s) 1039 - 1044
Section Interdisciplinary physics and related areas of science and technology
Published online 18 November 2005
Europhys. Lett., 72 (6), pp. 1039-1044 (2005)
DOI: 10.1209/epl/i2005-10338-1

Contour length fluctuations in polymer melts: A direct molecular proof

M. Zamponi1, M. Monkenbusch1, L. Willner1, A. Wischnewski1, B. Farago2 and D. Richter1

1  Institut für Festkörperforschung, Forschungszentrum Jülich - 52425 Jülich, Germany
2  Institut Laue-Langevin - B.P. 156X, Avenue des Martyrs 38042 Grenoble Cedex 9, France

received 1 September 2005; accepted in final form 20 October 2005
published online 18 November 2005

In entangled polymer melts, contour length fluctuations are supposed to lift the chain confinement starting from the chain ends. Using neutron spin echo spectroscopy on polyethylene chains of intermediate length, where only the center part is labeled, allows us to separate the contribution of contour length fluctuations to the dynamic structure factor and thereby explicitly prove the effect on a molecular level. While a corresponding fully labeled chain shows the relaxation by contour length fluctuations additional to the primary relaxation, the data of the center-labeled chain, where the visibility of the fluctuations is switched off, is in excellent agreement with results for a nearly infinite long chain, where contour length fluctuations are known to be negligible.

83.80.Sg - Polymer melts.
61.12.Ex - Neutron scattering (including small-angle scattering).

© EDP Sciences 2005