Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 27: POSTER Polymer Physics and Materials
CPP 27.7: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
Unexpected preparative effects on the properties of thin polymer films — •Anatoli Serghei1, Heiko Huth2, Christoph Schick2, and Friedrich Kremer1 — 1University of Leipzig, Institute for experimental physics I, 04103 Leipzig, Germany — 2University of Rostock, Physics Department, , 18051 Rostock, Germany
Thin supported PS films dewet a solid substrate when kept above Tg in vacuum (~ 3 mbar), while in high vacuum (10^-6 mbar), under identical experimental conditions, i.e. same thickness, temperature and annealing time, no dewetting takes place. When sandwiched between two thin metal electrodes a characteristic pattern is developed in ambient air above Tg, whereas no changes are observed in high vacuum or in a pure nitrogen atmosphere. These two seemingly unrelated phenomena are suggested to have a common physical origin: due to the presence of remanent oxygen in the immediate vicinity of the polymer films, chain scissions are induced, which result in a pronounced decrease of the average molecular weight. This causes an enhancement of the molecular mobility and a reduction of the corresponding glass transition temperature Tg, as proven by Broadband Dielectric Spectroscopy, AC-calorimetry and capacitive dilatometry. No shifts of the glass transition in thin PS films down to a thickness of 20 nm are detected when the samples are annealed in high vacuum and measured in a pure nitrogen atmosphere.
A. Serghei et al., Phys. Rev. E 71, 061801 (2005).