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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 46: Micro- and Nanofluidics II

CPP 46.4: Vortrag

Freitag, 18. März 2011, 11:30–11:45, ZEU 222

Influence of the solid/liquid interface on the flow dynamics of unentangled polymer melts — •Mischa Klos, Matthias Lessel, Oliver Bäumchen, and Karin Jacobs — Saarland University, Department of Experimental Physics, D-66041 Saarbrücken

Due to downsizing of microfluidic devices, the solid/liquid interface becomes more and more influential for liquid flow. In classic hydrodynamics, the velocity profile of a liquid flowing through a tube or over a surface extrapolates to zero close to a wall. By applying a hydrophobic coating to the solid surface it is possible to create a finite velocity of the liquid at the solid/liquid interface, known as slippage. Slippage is characterized by the extrapolation length of the flow profile, called slip length. In our experiments, liquid flow is induced by an internal driving force which drives the dewetting of thin polymer films on hydrophobic substrates. The slip length can be extracted by monitoring the dewetting dynamics of the emerging holes in the film or by characterizing the shape of the surrounding rim. Aside from the strong impact of inter-chain entanglements on slippage, also the type of hydrophobic substrate influences the slip length. We show results for thin polystyrene films flowing over an amorphous polymeric coating (AF1600) and different types of self-assembled monolayers of silanes. The AF1600 induces nearly no slip at the solid/liquid interface, in contrast to the silan surfaces, where the slip length reaches values from several hundreds of nanometers up to micrometers. We investigate whether slippage varies with the silane's chain length, its structure on the molecular level and the surface energy.