title: Nematic effects and strain coupling in entangled polymer melts under strong flow.
abstract: We use small-angle neutron scattering (SANS) to study labeled short chains with and without the influence of an entangled and highly stretched surrounding environment of longer chains. We find unequivocal evidence of nematic effects as the blend chains in steady state flow are stretched a factor ∼1.5 more from the presence of the long chain nematic field. In the pure melt we confirm that the nonaffine mean-field result ν=0.5 for the strain coupling is still valid for very fast flows, while in the nematic system our analysis predicts an increased coupling constant. We provide a structural explanation for the two first regimes of the nonlinear relaxation, particularly a transition regime where the long chains are relaxing in a sea of reptating short chains.
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Jacob J K
authors.initials: JJ
authors.lastname: Kirkensgaard
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Ludovica
authors.initials: L
authors.lastname: Hengeller
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Andriy
authors.initials: A
authors.lastname: Dorokhin
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Qian
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Garvey
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Almdal
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Hassager
authors.affiliation: Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
authors.forename: Kell
authors.initials: K
authors.lastname: Mortensen