title: Reduced interfacial entanglement density affects the boundary conditions of polymer flow.
abstract: Hydrodynamic boundary conditions play a crucial role in the flow dynamics of thin films and can be probed by the analysis of liquid front profiles. For long-chained polymer films it was reported that a deviation from a symmetric profile is a result of viscoelastic effects. In this Letter, however, evidence is given that merely a slip-boundary condition at the solid-liquid interface can lead to an asymmetric profile. Variation of molecular weight shows that slippage is directly linked to chain entanglements. We find a reduced entanglement density at the solid-liquid interface (factors 3 to 4), which stresses the importance of considering nonbulk polymer properties in the vicinity of an interface.
authors.affiliation: Department of Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Bäumchen
authors.forename: R
authors.initials: R
authors.lastname: Fetzer
authors.forename: K
authors.initials: K
authors.lastname: Jacobs