Experimental evidence of mosaic structure in strongly supercooled molecular liquids.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33767148.
- Also identified by DOI 10.1038/s41467-021-22154-8 and PMC identifier 7994800.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
When a liquid is cooled to produce a glass its dynamics, dominated by the structural relaxation, become very slow, and at the glass-transition temperature T<sub>g</sub> its characteristic relaxation time is about 100 s. At slightly elevated temperatures (~1.2 T<sub>g</sub>) however, a second process known as the Johari-Goldstein relaxation, β<sub>JG</sub>, decouples from the structural one and remains much faster than it down to T<sub>g</sub>. While it is known that the β<sub>JG</sub>-process is strongly coupled to the structural relaxation, its dedicated role in the glass-transition remains under debate. Here we use an experimental technique that permits us to investigate the spatial and temporal properties of the β<sub>JG</sub> relaxation, and give evidence that the molecules participating in it are highly mobile and spatially connected in a system-spanning, percolating cluster. This correlation of structural and dynamical properties provides strong experimental support for a picture, drawn from theoretical studies, of an intermittent mosaic structure in the deeply supercooled liquid phase.