Composition Dependence of Dynamic Heterogeneity Time- and Length Scales in [Omim][BF₄]/Water Binary Mixtures: Molecular Dynamics Simulation Study

Abstract

Composition dependence of four-point dynamic susceptibilities, overlap functions, and other dynamic heterogeneity (DH) parameters have been investigated by using all-atom molecular dynamics simulations for aqueous solutions of the ionic liquid (IL), 1-octyl-3-methyl imidazolium tetrafluoroborate ([Omim][BF4]) covering the pure-to-pure range. Upon addition of water in the IL, the DH time scales become faster and the four-point dynamic susceptibility time scale softens. Evidences for jump motions for both water and ions have been found from the simulated single particle displacements that show strong deviation from Gaussian distribution. Estimated dynamic correlation length for water reflects effects of IL, whereas those for ions remain largely insensitive to the mixture composition. Simulated structural aspects and DH time scales provide microscopic explanations to the existing experimental observations from time-resolved fluorescence and Kerr spectroscopic measurements.

Molecular insight into the microstructure and microscopic dynamics of pyridinium ionic liquids with different alkyl chains based on temperature response

“…3, the RDFs between the terminal carbon atoms of the alkyl chain were calculated at different temperatures. With the increase of the temperature, the RDFs show that the peaks of CT4-CT4 of [ 4 ] with the increase in temperature. Fig.…”

“…The second peak at 1.05 nm, which is the second shell, is relatively weak. With the increase in the temperature, the peaks of [ 4 ] with the change in the temperature. This difference is explained in the next section detailing the coordination number (CN).…”

“…According to Fig. 6(a) 4 ] may induce changes in the local structure because the three ILs show a similar composition, except for the different alkyl chains.…”

“…As a new type of green solvent, ILs are receiving increasing research attention. [3][4][5] According to the articles published in recent years, the research on ILs mainly focuses on organic reactions, materials chemistry, polymer chemistry, analytical chemistry, and the chemical industry. 6,7 ILs are also applied to other elds, such as energy, environment, bioscience, photoelectric information, and aerospace materials.…”

“…However, a limited amount of research has studied the structures and properties of pyridinium ILs via MD simulation in different temperatures. 26 In the present work, MD simulation was carried out to study the pure systems of Nbutylpyridinium tetrauoroborate ( 4 ]). The effects of temperature on the local microstructure and dynamics of the three ILs were compared by analyzing their radial distribution functions, spatial distribution functions, and correlation functions.…”