title: Impact of an irreversibly adsorbed layer on local viscosity of nanoconfined polymer melts.
abstract: We report the origin of the effect of nanoscale confinement on the local viscosity of entangled polystyrene (PS) films at temperatures far above the glass transition temperature. By using marker x-ray photon correlation spectroscopy with gold nanoparticles embedded in the PS films prepared on solid substrates, we have determined the local viscosity as a function of the distance from the polymer-substrate interface. The results show the impact of a very thin adsorbed layer (~7 nm in thickness) even without specific interactions of the polymer with the substrate, overcoming the effect of a surface mobile layer at the air-polymer interface and thereby resulting in a significant increase in the local viscosity as approaching the substrate interface.
authors.affiliation: Chemical and Molecular Engineering Program, Stony Brook University, Stony Brook, New York 11794-2275, USA. tkoga@notes.cc.sunysb.edu
authors.forename: Tadanori
authors.initials: T
authors.lastname: Koga
authors.forename: N
authors.initials: N
authors.lastname: Jiang
authors.forename: P
authors.initials: P
authors.lastname: Gin
authors.forename: M K
authors.initials: MK
authors.lastname: Endoh
authors.forename: S
authors.initials: S
authors.lastname: Narayanan
authors.forename: L B
authors.initials: LB
authors.lastname: Lurio
authors.forename: S K
authors.initials: SK
authors.lastname: Sinha