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Main and secondary relaxations of non-polymeric high-Tg glass formers as revealed by dielectric spectroscopy

Title data

Körber, Thomas ; Krohn, Felix ; Neuber, Christian ; Schmidt, Hans-Werner ; Rößler, Ernst A.:
Main and secondary relaxations of non-polymeric high-Tg glass formers as revealed by dielectric spectroscopy.
In: Physical Chemistry Chemical Physics. Vol. 22 (2020) Issue 16 . - pp. 9086-9097.
ISSN 1463-9084
DOI: https://doi.org/10.1039/D0CP00930J

Project information

Project financing: Bayerisches Staatsministerium für Wissenschaft, Forschung und Kunst
Deutsche Forschungsgemeinschaft

Abstract in another language

A series of high-Tg glass formers with Tg values varying between 347 and 390 K and molar masses in the range of 341 and 504 g mol−1 are investigated by dielectric spectroscopy. They are compared to paradigmatic reference systems. Differently polar side groups are attached to a rigid non-polar core unit at different positions. Thereby, the dielectric relaxation strength varies over more than two decades. All the relaxation features typical of molecular glass formers are rediscovered, i.e. stretching of the main (α-) relaxation, a more or less pronounced secondary (β-) process, and a fragility index quite similar to that of other molecular systems. The position of the polar nitrile side group influences the manifestation of the β-relaxation. The α-relaxation stretching displays the trend to become less with higher relaxation strength Δεα, confirming recent reports. Typical for a generic β-process is the increase of its amplitude above Tg, which is found to follow a power-law behaviour as a function of the ratio τα/τβ with a universal exponent; yet, its relative amplitude to that of the α-relaxation varies as does the temporal separation of both processes. The mean activation energy of the β-process as well as the width of the energy distribution gβ(E) increases more or less systematically with Tg. The latter is determined from the dielectric spectra subjected to a scaling procedure assuming a thermally activated process. Plotting gβ(E) as a function of the reduced energy scale E/Tg, the distributions are centred between 19–35 and their widths differ by a factor 2–3.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III > Chair Inorganic Chemistry III - Univ.-Prof. Dr. Jürgen Senker
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Macromolecular Chemistry I
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Macromolecular Chemistry I > Chair Macromolecular Chemistry I - Univ.-Prof. Dr. Hans-Werner Schmidt
Profile Fields
Profile Fields > Advanced Fields
Profile Fields > Advanced Fields > Polymer and Colloid Science
Research Institutions
Research Institutions > Affiliated Institutes
Research Institutions > Affiliated Institutes > Bavarian Polymer Institute (BPI)
Research Institutions > Collaborative Research Centers, Research Unit
Research Institutions > Collaborative Research Centers, Research Unit > SFB 840 Von partikulären Nanosystemen zur Mesotechnologie
Graduate Schools
Graduate Schools > Elite Network Bavaria
Graduate Schools > Elite Network Bavaria > Macromolecular Science
Result of work at the UBT: Yes
DDC Subjects: 500 Science
500 Science > 540 Chemistry
Date Deposited: 11 Dec 2020 10:01
Last Modified: 11 Dec 2020 10:07
URI: https://eref.uni-bayreuth.de/id/eprint/61007