We report evidence from broadband dielectric spectroscopy that the dynamics of the primary alpha- and secondary Johari-Goldstein (JG) beta-processes are strongly correlated in different glass-forming systems over a wide temperature T and pressure P range, in contrast with the widespread opinion of statistical independence of these processes. The alpha-beta mutual dependence is quantitatively confirmed by (a) the overall superposition of spectra measured at different T-P combinations but with an invariant alpha-relaxation time; (b) the contemporary scaling of the isothermal-pressure and isobaric-temperature dependences of the alpha-and beta-relaxation times as plotted versus the reduced variable T-g(P)/T where T-g is the glass transition temperature. These novel and model-independent evidences indicate the relevance of the JG relaxation phenomenon in glass transition, often overlooked by most current theories.
|Autori:||Kessairi K.; Capaccioli S; Prevosto D.; Lucchesi M.; Sharifi S.; Rolla P. A.|
|Titolo:||Interdependence of primary and Johari-Goldstein secondary relaxations in glass-forming systems|
|Anno del prodotto:||2008|
|Digital Object Identifier (DOI):||10.1021/jp800764w|
|Appare nelle tipologie:||1.1 Articolo in rivista|