A mechanism for ageing in a deeply supercooled molecular glass

Measurements of the decay of electric fields, formed spontaneously within vapour-deposited films of cis -methyl formate, provide the first direct assessment of the energy barrier to secondary relaxation in a molecular glass. At temperatures far below the glass transition temperature, the mechanism o...

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Bibliographic Details
Published in:Chemical communications (Cambridge, England) England), 2021-07, Vol.57 (52), p.6368-6371
Main Authors: Cassidy, Andrew, Jørgensen, Mads R. V, Glavic, Artur, Lauter, Valeria, Plekan, Oksana, Field, David
Format: Article
Language:English
Subjects:
Condensed Matter Physics
Den kondenserade materiens fysik
Electric fields
Fysik
Glass transition temperature
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Methyl formate
Molecular rotation
Natural Sciences
Naturvetenskap
Neutron scattering
Neutrons
Physical Sciences
Temperature
Vapor deposition
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Summary:Measurements of the decay of electric fields, formed spontaneously within vapour-deposited films of cis -methyl formate, provide the first direct assessment of the energy barrier to secondary relaxation in a molecular glass. At temperatures far below the glass transition temperature, the mechanism of relaxation is shown to be through hindered molecular rotation. Magnetically-polarised neutron scattering experiments exclude diffusion, which is demonstrated to take place only close to the glass transition temperature. A molecular glass spontaneously polarises upon growth. The temporal decay of this polarization is directly related to the rotation of molecular dipoles and we use this to track an ageing pathway in a deeply supercooled glassy solid.
ISSN:1359-7345
1364-548X
DOI:10.1039/d1cc01639c