Molecular observation of contour-length fluctuations limiting topological confinement in polymer melts

• Published in: Physical review letters Vol. 88; no. 5; p. 058301
• Main Authors: Wischnewski, A, Monkenbusch, M, Willner, L, Richter, D, Likhtman, A E, McLeish, T C B, Farago, B
• Format: Journal Article
• Language: English
• Published: United States 04-02-2002
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.88.058301

In order to study the mechanisms limiting the topological chain confinement in polymer melts, we have performed neutron-spin-echo investigations of the single-chain dynamic-structure factor from polyethylene melts over a large range of chain lengths. While at high molecular weight the reptation model is corroborated, a systematic loosening of the confinement with decreasing chain length is found. The dynamic-structure factors are quantitatively described by the effect of contour-length fluctuations on the confining tube, establishing this mechanism on a molecular level in space and time.