title: Direct observation of the transition from free to constrained single-segment motion in entangled polymer melts.
abstract: We report a direct determination of the time dependent mean-squared segment displacement of a polymer chain in the melt covering the transition from free to constraint Rouse relaxation along the virtual tube of the reptation model. This has been achieved by a neutron spin-echo (NSE) measurement of the segmental self-correlation function as conveyed by the spin-incoherent scattering from two fully protonated polymer melts, polyethylene and polyethylene propylene. Within the scenario of de Gennes reptation model a transition of the time dependence of segmental mean-squared displacements from proportional, variant t(1/2) to proportional, variant t(1/4) is expected and clearly corroborated by the incoherent NSE results.
authors.affiliation: Institut für Festkörperforschung, Forschungszentrum Jülich, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Wischnewski
authors.forename: M
authors.initials: M
authors.lastname: Monkenbusch
authors.forename: L
authors.initials: L
authors.lastname: Willner
authors.forename: D
authors.initials: D
authors.lastname: Richter
authors.forename: G
authors.initials: G
authors.lastname: Kali