Regensburg 2004 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 7: Physics of Polymers I
CPP 7.2: Vortrag
Montag, 8. März 2004, 14:15–14:30, H 37
Surface glass transition of monodisperse polystyrenes and their bimodal mixtures investigated by the embedding of noble metal nanoclusters and the XPS-charging effect — •Jörn Erichsen, Tesfaye Shiferaw, Jörn Kanzow, Ulrich Schürmann, Vladimir Zaporojtchenko, and Franz Faupel — Lehrstuhl für Materialverbunde, Faculty of Engineering,
The temperature dependent embedding process of noble metal nanoclusters into polymers was used to probe the surface glass transition. X-ray photoelectron spectroscopy (XPS) was applied to study the embedding of Au nanoclusters into polystyrene [1]. Previously a small decrease of glass transition temperature (Tg) at the surface compared to the bulk, which decreases at low Mw, was detected with this method [1]. The Tg of thin PS films was additionally determined by the charging and discharging during XPS measurements. Transmission electron microscopy (TEM) investigations yield the same cluster sizes and densities for a height and a low molecular weight. Therefore, probe size effects can be excluded. In order to understand the Tg depression in monodisperse polystyrenes we present measurements on bimodal mixtures of monodisperse polystyrenes (Mw = 3.5 and 1000 kg/mol). The results on the bimodal mixtures rule out the interpretation that the Tg depression at the surface is due to an enrichment of shorter chains.
[1] V. Zaporojtchenko, T. Strunskus, J. Erichsen, F. Faupel, Macromolecules, 34(5) (2001) 1125.