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Correlation between primary and secondary Johari-Goldstein relaxations in supercooled liquids: invariance to changes in thermodynamic conditions.

Mierzwa M, Pawlus S, Paluch M, Kaminska E, Ngai KL

Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland. michal.mierzwa@us.edu.pl

The primary alpha and the secondary Johari-Goldstein (JG) beta relaxations of supercooled glass-forming neat epoxy resin and 2-picoline in mixture with tristyrene are monitored by broadband dielectric relaxation spectroscopy at ambient pressure and elevated pressures. For different combinations of pressure and temperature that maintain the alpha-relaxation time constant, the frequency dispersion of the alpha relaxation is unchanged, as previously found in other glass-formers, but remarkably the JG beta-relaxation time remains constant. This is more clear evidence of a strong connection between the alpha- and JG beta-relaxation times, a fact that should be taken into account in the construction of a viable theory of glass transition.

Published 5 February 2008 in J Chem Phys, 128(4): 044512.
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