Dipartimento di Fisica, Università di Trento, Povo (Trento), Italy.
Van der Waals-Zeeman Institute, Institute of Physics/Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam, the Netherlands.
Nat Commun. 2021 Mar 25;12(1):1867. doi: 10.1038/s41467-021-22154-8.
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 its characteristic relaxation time is about 100 s. At slightly elevated temperatures (~1.2 T) however, a second process known as the Johari-Goldstein relaxation, β, decouples from the structural one and remains much faster than it down to T. While it is known that the β-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 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.
当液体冷却形成玻璃时，其动力学过程主要由结构弛豫主导，变得非常缓慢，在玻璃化转变温度 T 下，其特征弛豫时间约为 100 秒。然而，在稍高的温度（约 1.2T）下，第二种被称为 Johari-Goldstein 弛豫的过程β与结构弛豫解耦，并且在下降到 T 之前一直比结构弛豫快得多。虽然已知β过程与结构弛豫强烈耦合，但它在玻璃化转变中的特定作用仍存在争议。在这里，我们使用一种实验技术来研究β弛豫的空间和时间特性，并提供证据表明，参与其中的分子在系统跨越的、弥散的团簇中具有高度的流动性和空间连接性。这种结构和动力学性质的相关性为理论研究中提出的一种间歇性镶嵌结构模型提供了有力的实验支持，这种模型存在于深度过冷液体相中。
