Mesoscale Organization and Dynamics in Binary Ionic Liquid Mixtures

Abstract

The impact of mesoscale organization on dynamics and ion transport in binary ionic liquid mixtures is investigated by broadband dielectric spectroscopy, dynamic-mechanical spectroscopy,x-ray scattering, and molecular dynamics simulations. The mixtures are found to form distinct liquids with macroscopic properties that significantly deviate from weighted contributions of the neat components. For instance, it is shown that the mesoscale morphologies in ionic liquids can be tuned by mixing to enhance the static dielectric permittivity of the resulting liquid by as high as 100% relative to the neat ionic liquid components. This enhancement is attributed to the intricate role of interfacial dynamics associated with the changes in the mesoscopic aggregate morphologies in these systems. These results demonstrate the potential to design the physicochemical properties of ionic liquids through control of solvophobic aggregation.Elucidating the influence of mesoscale organization on the dynamics and transport properties of ionic liquids is critical to developing design criteria for their applications in chemical synthesis, nanoparticle growth, biomass processing, batteries, solar cells, and supercapacitors.[1-10] In the past decade, the formation of mesoscale polar and non-polar domains in ionic liquids with substantial non-polar, alkyl side groups was recognized in detailed x-ray scattering, neutron scattering, and molecular dynamics (MD) simulation studies. [11][12][13][14][15][16] Mesoscale organization has been used to qualitatively explain numerous experimental findings which imply spatially and temporally distinct regions within bulk ionic liquids. [11,[17][18][19][20][21][22][23][24][25][26] Recent studies suggest that the existence and dynamics of the aggregates in neat ionic liquids, associated with fluctuations of the polar and non-polar regions, correlate strongly with many of the physicochemical properties of ionic liquids including transport properties such as zero-shear viscosity, dc ionic conductivity, and static dielectric permittivity. [27][28][29][30][31][32] However, no efforts to exploit the mesoscale organization to design novel ionic liquids with unique physical and chemical properties have been reported. In this work, it is demonstrated that by mixing ionic liquids with varying degrees of solvophobic aggregation, it is feasible to design distinct liquids with macroscopic properties that significantly deviate from weighted contributions of the neat components.The local organization, or morphology, of the mesoscale aggregates is in part determined by the relative volume fractions of the polar and non-polar groups of the component ions.[11] In amphiphilic imidazolium, pyrrolidinium, piperidinium, quaternary phos-

In Silico Elucidation of Molecular Picture of Water–Choline Chloride Mixture

“…A very recent investigation combines experimental and theoretical observations to probe the mesoscale organization of a mixture of binary ionic liquid. This study reports that the behavior of the mixture is completely distinct compared to the constituents . Hence, an understanding of the molecular level interaction of the constituents governed by the extended hydrogen-bond network is imperative.…”

Microscopic structural features of water in aqueous–reline mixtures of varying compositions

“…[17][18][19][20] Several studies related to the morphological properties of ionic liquids (IL) guide the community regarding the wise use of the solvent, which is largely lacking in the case of DES. [21][22][23][24][25][26][27] Reline is one of the most celebrated and highly used DESs, where urea (H2N-CO-NH2) is used as the hydrogen bond donor with choline chloride ([(CH3)3N-(CH2)2-OH] + Cl -) (ChCl) in 2:1 molar ratio. 28,29 Apart from its biodegradability and economic viability, 17,28 reline also has ample industrial applications.…”

Computer Simulations of Deep Eutectic Solvents: Challenges, Solutions, and Perspectives

“…We refer to current publications for the details. No DES FF/Corrections Topic of the Publication Reference 1 1-ethyl-3-methylimidazolium chloride:Urea Different molar ratios CL&P OPLS-AA Investigation of DES structure [ 231 ] 2 1-octyl-3-methylimidazolium: Tetrafluoroborate 1-ethyl-3-methylimidazolium:Tetrafluoroborate Different molar ratios CL&P Investigation of DES structure [ 370 ] 3 Acetamide:LiBr (3.5:1) CHARMM 27 only/no corrections Support to experiment [ 253 ] 4 Acetamide:LiClO 4 (3.5:1) CHARMM 27 + separate parameters for ions Mechanisms of DES components motion [ 249 ] 5 Acetamide:LiClO 4 (3.5:1) CHARMM 27 + separate parameters for ions Mechanism of Acetamide in Deep Eutectic Solvents [ 250 ] 6 Acetamide:LiClO 4 (3.5:1) Acetamide:LiNO 3 (3.5:1) Acetamide:LiBr (3.5:1) CHARMM 27 + separate parameters for ions Orientation jumps of acetamide molecules [ …”