Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 11: Glasses I (joint session DF/DY)

DY 11.5: Vortrag

Dienstag, 26. Februar 2008, 10:45–11:00, EB 407

Glassy dynamics in the mono-, di- and trimer of glass-forming propylene glycol — •Melanie Köhler, Robert Wehn, Peter Lunkenheimer, and Alois Loidl — Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg

We report broadband dielectric spectra on glass-forming propylene glycol and its di- and trimer. Aside of the α-relaxation, we focus on the dynamics at higher frequencies, which is believed to play an important role for the glass transition. While the monomer of propylene glycol has a well-developed excess wing, a characteristic spectral feature of glassy dynamics beyond the α-relaxation [1], the di-and trimers show a Johari-Goldstein β-relaxation [2]. Interestingly, as revealed by long-time aging experiments performed in our group [1], the excess wing in propylene glycol also can be described as signature of a β-relaxation. The data is analysed in the framework of different models, as the coupling model and the minimal model [3, 4]. In addition we treat the relation between the Cole-Cole peak, recently suggested within an extended version of mode coupling theory [5], and the spectral properties of the experimentally detected β-relaxation in these glass formers. Also first results in the region beyond GHz frequencies, where additional fast processes are expected, are provided. [1] K.L. Ngai et al., J. Chem. Phys. 115, 1405 (2001). [2] K. Grzybowska et al., J. Chem. Phys. 125, 044904 (2006). [3] K. L. Ngai, Comments Solid State Phys. 9, 127 (1979). [4] J. C. Dyre, N. B. Olsen, Phys. Rev. Lett. 91, 155703 (2003). [5] W. Götze and M. Sperl, Phys. Rev. Lett. 92, 105701 (2004).