Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 19: Poster: New Methods, Thin Polymer Films, Monolayers
CPP 19.23: Poster
Thursday, April 5, 2001, 12:30–15:00, AT1
Dewetting at a Polymer-Polymer Interface: Film Thickness Dependence — •C. Wang1, M. Geoghegan2, H. Elbs1, and G. Krausch1 — 1Physikalische Chemie II, Universität Bayreuth,, D-95440 Bayreuth — 2Dept. of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
We have used optical microscopy and scanning probe microscopy to study the dewetting dynamics of polystyrene (PS) from polymethylmethacrylate (PMMA) on silicon substrates. The upper PS layer has a higher viscosity than the lower PMMA layer (ηPMMA < ηPS / ΘE). Varying the thickness of the PMMA layers we have observed different dewetting ranges: If the lower layer is about 5 nm thick, dewetting of the upper layer does not occur, probably because dispersive forces stabilize the system. In the range of 20 to 100 nm, the radius of the dewetting holes grow linearly with annealing time (t), which shows strong influence of the solid silicon substrate on the system, while after annealing to some extent, unusual bilayer-dewetting takes place, namely, new holes form in PMMA layer within the previous holes in the PS layer. Between 100 nm and 600 nm, the holes grow as t2/3. Increasing the thicknesses of the upper layers from 10 nm to 270 nm, the growing speed of the holes decreases signifiantly and the density of the holes decreases. Systematic studies of the thickness dependence of the dewetting speed show that the experimental results are in reasonable agreement with theoretical predictions.