Nature and properties of the Johari-Goldstein β-relaxation in the equilibrium liquid state of a class of glass-formers
Previous dielectric relaxation measurements of glycerol and propylene carbonate and new results on propylene glycol performed below the conventional glass transition temperatures T_(g) after long periods of aging all show that the excess wing (a second power law at higher frequencies) in the isother...
| Autores: | , , , , , |
|---|---|
| Formato: | artículo |
| Fecha de publicación: | 2001 |
| País: | España |
| Recursos: | Universidad Complutense de Madrid (UCM) |
| Repositorio: | Docta Complutense |
| Idioma: | inglés |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/59632 |
| Acesso em linha: | https://hdl.handle.net/20.500.14352/59632 |
| Access Level: | acceso abierto |
| Palavra-chave: | 537 Dielectric alpha-relaxation Supercooled liquids Forming liquids Propylene carbonate Secondary relaxations Kohlrausch exponent Coupling model Transition Dynamics Spectroscopy. Electricidad Electrónica (Física) 2202.03 Electricidad |
| Resumo: | Previous dielectric relaxation measurements of glycerol and propylene carbonate and new results on propylene glycol performed below the conventional glass transition temperatures T_(g) after long periods of aging all show that the excess wing (a second power law at higher frequencies) in the isothermal dielectric loss spectrum, develops into a shoulder. These results suggest that the excess wing, a characteristic feature of a variety of glass-formers, is the high frequency flank of a Johari–Goldstein β-relaxation loss peak submerged under the α-relaxation loss peak. With this interpretation of the excess wing assured, the dielectric spectra of all three glass-formers measured at temperatures above T_(g) are analyzed as a sum of a α-relaxation modeled by the Fourier transform of a Kohlrausch–Williams–Watts function and a β-relaxation modeled by a Cole–Cole function. Good fits to the experimental data have been achieved. In addition to the newly resolved β-relaxation on propylene glycol, the important results of this work are the properties of the β-relaxation in this class of glass-formers in the equilibrium liquid state obtained over broad frequency and temperature ranges. |
|---|