Jul 3 – 6, 2017
Europe/Warsaw timezone

Scaling of the dielectric response of supercooled disordered phases

Jul 4, 2017, 1:00 PM
oral presentation Soft matter and glass formers Soft Matter


Dr Miroslaw Galazka (Institute of Nuclear Physics Polish Academy of Sciences)


`Spectrum of a dielectric permittivity for supercooled disordered phases most often is composed of two relaxation processes [1]: a main relaxation process (called $\alpha$ process) followed by resolved, unresolved (also called ‘excess wing phenomena’), or both secondary processes ($\beta$ processes). Although there are many models describing dielectric relaxation [2-6] none of them describes the relaxation processes in supercooled disordered phases with a good precision, because of some simplifications introduced. Debye model [2] describes relaxation for non-interacting electric dipoles or electric dipoles in diluted non-polar medium whereas Debye-like models, i.e. Cole-Cole [3], Cole-Davidson [4], Havriliak-Negami [5], describe relaxation for non-interacting electric dipoles in viscous medium. Therefore, some scaling equations of the dielectric response were proposed [7-9] to describe molecular dynamics as a function of frequency of measuring field for various temperatures. However, they are limited to scaling of the imaginary part of dielectric permittivity only [7-9], and Nagel and co-authors model [7-8] refers in fact to systems with ‘special’ values of long-range and short-range correlation parameters of molecular interactions. Therefore, we have proposed a general form of scaling equation [10-11] that can be applied to the imaginary part of permittivity $\epsilon$”($f$) as well as to the real part of permittivity $\epsilon$’($f$)-$\epsilon_\infty$. The proposed scaling of the dielectric response applied to supercooled disordered phases, i.e. supercooled isotropic liquid phase and supercooled plastic-crystal phase, shows that behavior of resolved and/or unresolved $\beta$ relaxations strictly depends on the parameters of the main relaxation process. One can conclude that the main relaxation process and the secondary ones are not independent processes.` References [1] A. Kudlik et al., `$\textit{J. Non-Cryst. Solids}$` `$\textbf{235-237}$` (1998) 406. [2] F. Kremer, A. Söchnhals, `$\textit{Broadband Dielectric Spectroscopy}$`, Springer-Verlag Berlin Heidelberg (2003). [3] K. S. Cole, R. H. Cole, `$\textbf{J. Chem. Phys.}$` `$\textbf{9}$` (1941) 341. [4] D. W. Davidson, R. H. Cole, `$\textit{J. Chem. Phys.}$` `$\textbf{18}$` (1951) 1417. [5] S. Havriliak, C. A. Negami, `$\textit{J. Polym. Sci. Part C}$` `$\textbf{14}$` (1966) 99. [6] L. A. Dissado, R. M. Hill, `$\textit{Proc. R. Soc. A}$` `$\textbf{390}$` (1983) 131. [7] N. Menon, S. R. Nagel, `$\textit{Phys. Rev. Lett.}$` `$\textbf{71}$` (1993) 4095. [8] P. K. Dixon, L. Wu, S. R. Nagel, B. D. Williams, J. P. Carini, `$\textit{Phys. Rev. Lett.}$` `$\textbf{65}$` (1990) 1108. [9] Z. Dendzik, M. Paluch, Z. Gburski, J. Zioło, `$\textit{J. Phys.: Condens. Matt.}$` `$\textbf{9}$` (1997) L339. [10] M. Gałązka, E. Juszyńska-Gałązka, N. Osiecka, M. Massalska-Arodź, A. Bąk, `$\textit{J. Appl. Phys.}$` `$\textbf{118}$` (2015) 064101. [11] M. Gałązka, E. Juszyńska-Gałązka, N. Osiecka, A. Bąk, `$\textit{Phase Transitions}$` `$\textbf{89}$` (2016) 341. `Acknowledgments` `Partial support by the 2014-2016 PAS-CNR bilateral project “Studies of phase polymorphism and dynamics in selected soft materials” and by the 2017-2019 PAS-CNR bilateral project “Multidisciplinary studies of structural and dynamic properties of glass-forming compounds” is acknowledged.`

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Dr Miroslaw Galazka (Institute of Nuclear Physics Polish Academy of Sciences)

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