Regensburg 2007 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 5: Glass I (joint session with DY)
DF 5.9: Vortrag
Dienstag, 27. März 2007, 12:15–12:30, H23
Complex Dynamics in a Binary Glass Former investigated by Dielectric Spectroscopy — •Philipp Gutfreund, Thomas Blochowicz, and Bernd Stühn — TU Darmstadt
Previous work on binary glass forming mixtures showed pronounced dynamic heterogeneities and a broad distribution of relaxation times of the smaller molecules in the mixture and in some cases even a distinct secondary relaxation peak was observed. It was also demonstrated that an additional power law contribution at the high frequency side of the main relaxation peak in neat glass-formers, called excess wing, can be separated as a distinct secondary relaxation peak if the molecule is contained in a slower matrix.
In the present work a mixture of Methyl-Tetrahydrofuran (M-THF) in Tristyrene was investigated by dielectric spectroscopy. The dielectric spectra are dominated by the smaller M-THF molecules due to the much stronger dipole moment. Calorimetry measurements show full miscibility in the whole concentration and temperature range. Pure M-THF is known to show a pronounced high frequency wing and a small secondary relaxation process, it is shown that in the mixtures several other processes emerge. The fastest of these processes seems to show certain typical signs of liquid dynamics far below TG of the mixture. The fact of coexisting glassy and liquid states in a binary mixture below TG was already shown in NMR measurements [1] and was previously anticipated by theoretical considerations [2].
[1] T. Blochowicz et al., J. Phys. Chem. B 103 (1999) 4032
[2] J. Bosse and Y. Kaneko, Phys. Rev. Lett. 74 (1995) 4023