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DF: Fachverband Dielektrische Festkörper

DF 9: Glasses and Glass Transition I (joint session with CPP, DY)

DF 9.3: Vortrag

Montag, 11. März 2013, 15:45–16:00, H34

Calorimetric glass transition of ultathin films of homopolymers and their blends — •Huajie Yin and Andreas Schönhals — BAM Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin, Germany

Glass transition behavior of different ultrathin polymer films (down to around 10 nm) was investigated by specific heat spectroscopy using differential AC calorimetry. For thin homopolymer films like polystyrene (PS) and poly(vinyl methyl ether) (PVME), no thickness dependence of dynamic glass transition temperature was observed down to 10 nm. Furthermore, the width of the glass transition is independent of the film thickness which indicates that the extent of the cooperativity is essentially smaller than 10 nm. For polymer blend thin films in the case of PS/PVME with the weight fraction of 50/50, the dynamic glass transition temperature was found to be decreasing with reducing the film thickness. This phenomenon is explained in terms of surface enrichment of PVME in the polymer blend system where PVME has a lower surface energy than PS. X-ray photoelectron spectroscopy (XPS) was used to probe the surface composition in order to confirm such surface enrichment phenomena.