Low-temperature dynamics in amorphous polymers and low-molecular-weight glasses-what is the difference?

Titelangaben

Eremchev, Ivan Yu. ; Vainer, Yury G. ; Naumov, Andrei V. ; Kador, Lothar:
Low-temperature dynamics in amorphous polymers and low-molecular-weight glasses-what is the difference?
In: Physical Chemistry Chemical Physics. Bd. 13 (2011) Heft 5 . - S. 1843-1848.
ISSN 1463-9076
DOI der Verlagsversion: https://doi.org/10.1039/c0cp01690j

Volltext

Format: PDF Name: c0cp01690j.pdf Version: Veröffentlichte Version Verfügbar mit der Lizenz Deutsches Urheberrecht. Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt werden. Darüber hinaus bedürfen die Vervielfältigung, Bearbeitung, Verbreitung und jede Art der Verwertung der schriftlichen Zustimmung des jeweiligen Rechteinhabers.

Download (1MB)

Abstract

Numerous experiments have shown that the low-temperature dynamics of a wide variety of disordered solids is qualitatively universal. However, most of these results were obtained with ensemble-averaging techniques which hide the local parameters of the dynamic processes. We used single-molecule (SM) spectroscopy for direct observation of the dynamic processes in disordered solids with different internal structure and chemical composition. The surprising result is that the dynamics of low-molecular-weight glasses and short-chain polymers does not follow, on a microscopic level, the current concept of low-temperature glass dynamics. An extra contribution to the dynamics was detected causing irreproducible jumps and drifts of the SM spectra on timescales between milliseconds and minutes. In most matrices consisting of small molecules and oligomers, the spectral dynamics was so fast that SM spectra could hardly or not at all be recorded and only irregular fluorescence flares were observed. These results provide new mechanistic insight into the behavior of glasses in general: At low temperatures, the local dynamics of disordered solids is not universal but depends on the structure and chemical composition of the material.