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BP: Fachverband Biologische Physik
BP 16: Poster - Glasses / Stat. Phys. Bio. / Networks (joint DY/BP/CPP/SOE)
BP 16.1: Poster
Tuesday, April 1, 2014, 09:30–12:30, P1
Investigation of the behavior of binary mixtures upon variation of the dynamic asymmetry — •Marie-Luise Braatz1, Sebastian Schramm1, Thomas Blochowicz1, Bernd Stühn1, and Bernhard Frick2 — 1Experimental Condensed Matter Physics, TU Darmstadt, Germany — 2Institut Laue Langevin, Grenoble, France
We study dynamically asymmetric binary mixtures comprised of polystyrene and the small molecule methyl tetrahydrofuran (MTHF). The blends are fully miscible on supercooling but still exhibit two glass transition temperatures. Between these two temperatures MTHF relaxes in a matrix of polystyrene, showing the signature of geometrical confinement on the nanoscale in its dynamic properties. Among the interesting characteristics observed, is a transition from fragile to strong behavior of the time constants and in some cases features of a type-A glass transition are found.
We study the behavior of these characteristics upon varying the molecular weight and thereby the dynamic asymmetry of the mixture as well as the concentration of the small molecules. Dielectric spectroscopy, depolarized dynamic light scattering and quasielastic neutron scattering are combined to cover a dynamic range of 1ps to 1000s.
Our results are compared to theoretical predictions that expect fragile-strong transitions and type-A glass transitions to be most pronounced at low concentrations of the small molecules and large dynamic asymmetries.