Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 23: Polymer films I
CPP 23.2: Vortrag
Dienstag, 8. März 2005, 14:15–14:30, TU C130
Shape of Dewetting Fronts: Impact of Slippage — •Renate Konrad1, Barbara Wagner2, Andreas Münch3, and Karin Jacobs1 — 1FR 7.2 Experimental Physics - Soft Matter, Saarland University, D-66123 Saarbrücken — 2WIAS, Mohrenstr. 39, D-10117 Berlin — 3Institute of Mathematics, Humboldt University Berlin, D-10099 Berlin
A liquid film that retracts from a non-wettable solid surface exhibits a peculiar profile that depends on parameters like the contact angle, the effective interface potential and the viscous and/or viscoelastic behavior of the liquid. We show that under certain conditions the profile also reacts to a change in the solid/liquid boundary condition, i.e. the sliding friction at the interface, which can be retraced to a change in the slip length. The profiles are determined by scanning force microscopy.
A thin macromolecular film (polystyrene of low molecular weight) is prepared on a smooth, hydrophobized Si wafer. Hydrophobicity was achieved by preparing two different types of self-assembled monolayers of silanes on the surface, octadecyl- (OTS) and dodecyltrichlorosilane (DTS), respectively. We discuss the influence of the two monolayers on surfaces roughness and on contact angle as well as on the dewetting velocity of the polystyrene film. New theoretical studies can explain the difference in front profile by assuming a change in slip length. Since slippage can enhance the flow rate also on a macro-scale, slippage is an important issue in the design of microfluidic devices such as mixers etc. The vision is thus to be capable to tailor surfaces in their ability to enhance slippage.