Abstract
In this work, we show how the structure and intermolecular interactions affect the dynamic heterogeneity of aprotic ionic liquids. Using calorimetric data for 30 ionic samples, we examine the influence of the strength of van der Waals and Coulombic interactions on dynamic heterogeneity. We show that the dynamic length scale of spatially heterogeneous dynamics decreases significantly with decreasing intermolecular distances. Additionally, we assume that the magnitude of the number of dynamically correlated molecules at the liquid–glass transition temperature can be treated as an indicator for a dynamical crossover.
Highlights
The concept of dynamic heterogeneity of supercooled liquids has been extensively studied[1−9] since the work of Adam and Gibbs.[10]
The sizes of cooperatively rearrangement regions (CRRs) do not have to be constant in time and/or space, and the dynamics of molecules, which belong to different regions, are not identical.[11−14] molecules only a few nanometers away from each other may have relaxation rates that differ by several orders of magnitude
The main aim of our work is to systematically study the dynamic heterogeneity in various aprotic ionic liquids
Summary
The concept of dynamic heterogeneity of supercooled liquids has been extensively studied[1−9] since the work of Adam and Gibbs.[10] Near the liquid−glass transition temperature, Tg, the dynamics freezes drastically, while the structure of the system changes only slightly. Such abnormal molecular dynamics behavior is often rationalized in terms of correlated motions of the neighboring molecules. These cooperating domains’ size increases as the temperature drops, which means that larger and larger groups of molecules in the supercooled liquid move cooperatively when approaching the glassy state.
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