Primary α and secondary β relaxation dynamics of meta-toluidine in the liquid state investigated by broadband dielectric spectroscopy

• Published in: The Journal of chemical physics Vol. 147; no. 8; p. 084506
• Main Authors: Švajdlenková, H, Ruff, A, Lunkenheimer, P, Loidl, A, Bartoš, J
• Format: Journal Article
• Language: English
• Published: United States 28.08.2017
• ISSN: 1089-7690
• DOI: 10.1063/1.5000257

We report a broadband dielectric spectroscopic (BDS) study on the clustering fragile glass-former meta-toluidine (m-TOL) from 187 K up to 289 K over a wide frequency range of 10 -10 Hz with focus on the primary α relaxation and the secondary β relaxation above the glass temperature T . The broadband dielectric spectra were fitted by using the Havriliak-Negami (HN) and Cole-Cole (CC) models. The β process disappearing at T = 1.12T exhibits non-Arrhenius dependence fitted by the Vogel-Fulcher-Tamman-Hesse equation with T in accord with the characteristic differential scanning calorimetry (DSC) limiting temperature of the glassy state. The essential feature of the α process consists in the distinct changes of its spectral shape parameter β marked by the characteristic BDS temperatures T and T . The primary α relaxation times were fitted over the entire temperature and frequency range by several current three-parameter up to six-parameter dynamic models. This analysis reveals that the crossover temperatures of the idealized mode coupling theory model (T ), the extended free volume model (T ), and the two-order parameter (TOP) model (T ) are close to T , which provides a consistent physical rationalization for the first change of the shape parameter. In addition, the other two characteristic TOP temperatures T and T are coinciding with the thermodynamic Kauzmann temperature T and the second change of the shape parameter at around T , respectively. These can be related to the onset of the liquid-like domains in the glassy state or the disappearance of the solid-like domains in the normal liquid state.