Regensburg 2002 – wissenschaftliches Programm

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SYPF: Struktur und Dynamik in dünnen Polymerfilmen

SYPF 1: Structure and Dynamics in Thin Polymer Films

SYPF 1.13: Vortrag

Donnerstag, 14. März 2002, 16:10–16:30, H37

Molecular dynamics in thin polymer films — •Lutz Hartmann, Wladimir Gorbatschow, Jörg Hauwede, and Friedrich Kremer — Faculty of Physics, University of Leipzig, Linnéstr. 5, 04103 Leipzig

Both, structural and dynamic properties of polymers confined to thin films have been investigated extensively within the last years. Dielectric relaxation spectroscopy (DRS) has turned out to be a convenient experimental technique to measure molecular fluctuations of polar moieties in such systems in a broad frequency and temperature range. Results obtained by DRS for the dynamics in thin spin-coated films of isotactic poly(methyl methacrylate) (i-PMMA) and in grafted layers of poly(γ-benzyl-L-glutamate) (PBLG) and of poly(dimethyl siloxane) (PDMS) can be summarized as follows: (i) The α-relaxation in thin films of i-PMMA shows a dependence on the film thickness concerning its width, its dielectric strength and its maximal relaxation time. This is explained by a fraction of immobilized polymer chains which does not contribute to the relaxation time distribution. The thickness dependence of the glass transition temperature in these films is discussed with regard to models for the glass transition in thin polymer films and to the role of the interaction between the polymer film and the substrate. (ii) The relaxation processes in grafted layers show distinct differences to their pendants in the bulk. In case of PBLG this can be understood by a model of restricted rotational diffusion. The findings on grafted PDMS are presumably caused by an altered density with respect to the bulk.