Hamburg 2001 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 46: Poster
DY 46.64: Poster
Donnerstag, 29. März 2001, 15:45–18:15, Foyer S\ 3
Comparison of the Surface and Bulk Glass Transition of Polystyrene — •R. Weber1, M. Tolan1, J. Stettner1, O. H. Seeck2, and W. Press1 — 1Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, Leibnizstraße 19, 24098 Kiel — 2IFF8,7 FZ Jülich GmbH, 52425 Jülich
The surface of polystyrene (PS) films of different molecular weights MW decorated with gold nanoclusters was investigated by x-ray reflectivity measurements. The reflectivity data were taken for polystyrene samples of MW=3800, 44000 and 212000 at beamlines W1.1 and D4.1 at HASYLAB, DESY, using a wavelength of λ=1.18 Å. The thicknesses of the films were much larger than the radii of gyration of the different PS samples. By annealing the films above the glass transition temperature Tg an embedding process of the clusters into the polymer occurs. This process starts at a sufficiently low viscosity and may be regarded as a probe of the glass transition in the near surface region of the PS films. Simultaneously the thermal expansion of the entire film and hence its bulk behavior were monitored. For the higher molecular weights a lowering of the viscosity in a near surface region could already be seen at temperatures below the bulk glass transition temperature Tg. In contrast to these observations the sample with MW=3800 did not show a significant decrease of Tg near the surface.