8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P4.45High-frequency dynamics of the PEG/water eutecticcomposition mixtures measured bytemperature-scanning double-scattering BrillouinspectroscopyMikolaj Pochylski 11 Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614, Poznań,PolandThe PEG/Water mixtures of eutectic composition were prepared for PEG polymers of different molarweight. The samples were measured using Temperature-Scanning Double-Scattering BrillouinSpectroscopy (TS-DS-BS) method. The Double-Scattering 90A/90R geometry applied, allow forsimultaneous measurement of the two longitudinal phonon frequencies (both at GHz frequencyrange) at two different exchanged wave-vectors [1]. This provide the possibility of experimentaldetermination of the opto-acoustic dispersion function, Q, at given temperature. The temperaturedependence of Q function was obtained by the temperature-scan (1-2K/min) in a range 170 - 370K(depending on the sample). It was found that in each of the sample examined, Q(T) dependenceindicates the existence of high-frequency relaxation process. The Q function is a frequency derivativeof the real part of longitudinal modulus. Q(T) dependence can be calculated knowing theproper model for a relaxation of the modulus and the temperature dependence of the relaxationtime [2]. Quantitative analysis performed shows that detected process is broader then the Debyeprocess and proceed with non-Arrhenius dependence of the relaxation time. [1] H. H. Krbecek, W.Kupisch, M. Pietralla, Polimer 37, 3483 (1996). [2] M. Pochylski, J. Gapiński, J. Phys. Chem. B114, 2644 (2010).45