Surface glass transition in bimodal polystyrene mixtures
Chair for Multicomponent Materials, Institute for Materials Science, Christian-Albrechts University at Kiel, Kaiserstr. 2, 24143, Kiel, Germany
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Accepted: 23 October 2007
Published online: 23 November 2007
Using the cluster-embedding method of V. Zaporojchenko et al. (Macromolecules 34, 1125 (2000)), we measured the glass transition temperature T g at the polystyrene/vacuum interface of bimodal mixtures of monodisperse polystyrenes of 3.5k and 1000k. Embedding of ≈ 1 nm Au clusters was monitored in situ by X-ray photoelectron spectroscopy (XPS). The clusters were formed by evaporation of Au onto the polymer surface. Only one glass transition was observed in the mixtures. The surface glass transition temperatures are correlated to but are below the bulk values of the mixtures and obey the Gordon-Taylor equation. The results suggest that the earlier reported molecular-weight dependence of the surface glass transition is not due to segregation of short chains to the surface.
PACS: 61.41.+e Polymers, elastomers, and plastics – / 64.70.Pf Glass transitions – / 68.47.Mn Polymer surfaces –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2007