Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: POSTERS Micro- and Nanofluidics

CPP 22.9: Poster

Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A

Thin dewetting polymer films: Fingering and the effect of interfaces — •Ludovic Marquant, Frank Müller, Julia Mainka, Oliver Bäumchen, and Karin Jacobs — Saarland University, Experimental Physics, D-66041 Saarbrücken, Germany

The dynamics of supported polymer thin films is studied along two aspects, which are the behaviour of films in bulk conditions (h> 100 nm) and the deviation from the bulk behaviour for smaller film thicknesses. First, we investigate the dynamics of the last stage of dewetting of a polymer melt from a hydrophobized substrate, where fingers are initiated by amplified fluctuations created by the growth of the rim (liquid moving front), analogue to the Rayleigh-Plateau-Instability. Film thickness and slippage influence the occurrence of the fingers structure. We demonstrate, backed by theoretical support, that slippage acts on the geometry of bulges, which become more asymmetric as the slip length increases. The system we use is a 100 nm polystyrene film prepared on top of differently hydrophobized Si wafer. Furthermore, we investigate the dynamics of the polymer at interfaces regarding the change of the glass transition temperature as we depart from bulk conditions. For molecules smaller than 300 kg/mol, it has been shown that the shift of Tg is not due to the geometrical finite size effect because the shift is independent of molecular weight. This phenomenon, studied by NMR, is explained by an enhanced molecular mobility at the free polymer interface. As NMR takes place in liquids and therefore affects the surface tension of polystyrene, we investigate in situ ellipsometry measurements of Tg with various liquids surrounding the film.