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Titolo:
The methyl group as a built-in probe of the glassy dynamics in propylene carbonate
Autore:
Qi, F; Bohmer, R; Sillescu, H;
Indirizzi:
Univ Mainz, Inst Phys Chem, D-55099 Mainz, Germany Univ Mainz Mainz Germany D-55099 Inst Phys Chem, D-55099 Mainz, Germany
Titolo Testata:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
fascicolo: 18, volume: 3, anno: 2001,
pagine: 4022 - 4028
SICI:
1463-9076(20010915)3:18<4022:TMGAAB>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR-MAGNETIC-RESONANCE; BETA-RELAXATION; SECONDARY RELAXATION; SUPERCOOLED LIQUIDS; DIELECTRIC RESPONSE; DEUTERON NMR; TRANSITION; FORMERS; REORIENTATIONS; TEMPERATURE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
55
Recensione:
Indirizzi per estratti:
Indirizzo: Bohmer, R Univ Mainz, Inst Phys Chem, D-55099 Mainz, Germany Univ Mainz Mainz Germany D-55099 Chem, D-55099 Mainz, Germany
Citazione:
F. Qi et al., "The methyl group as a built-in probe of the glassy dynamics in propylene carbonate", PHYS CHEM P, 3(18), 2001, pp. 4022-4028

Abstract

Deuteron nuclear magnetic resonance was employed to study primarily the glassy phase of the fragile glass-former propylene carbonate; selectively deuterated at the methyl group. The analysis of temperature dependent line shapes allowed us to map out the energy barrier distribution below the glass transition temperature. The results were compared to measurements of spin-relaxation times. We determined the relative width of the barrier distribution and the extent of the decoupling between the methyl group rotation time and the structural relaxation time near the glass transition. These, findings are discussed in the context of what has been reported for secondary relaxation processes in other glass-formers. Stimulated echo experiments on propylene carbonate demonstrate that, while in the supercooled liquid small angle reorientations dominate, in the glass the methyl group performs 120 degrees (or 60 degrees) jumps.

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Documento generato il 19/09/20 alle ore 09:17:09