Physicochemical and Structural Properties of a Hydrophobicity/Hydrophilicity Switchable Ionic Liquid

Abstract

Herein, we report the physicochemical and structural properties of a new solubility-switchable ionic liquid (IL) comprising the glycerammonium (GA) cation with a hydrophilic group, the GA cation attached to an acetal-based protective group [protected GA (PGA)], and bis-(trifluoromethanesulfonyl)amide (TFSA). The interionic volumes (V inter ) of the hydrophobic [PGA][TFSA] and hydrophilic [GA][TFSA] ILs were evaluated based on solution density, revealing weaker ion−ion interactions in these relative to conventional ILs. The [PGA][TFSA] and [GA][TFSA] also exhibit poor ion-conducting properties, with up to an order of magnitude lower ionic conductivity (σ) and self-diffusion coefficient (D), as compared with conventional ILs. Radial distribution functions derived from high-energy X-ray total scattering experiments [G exp (r)] and molecular dynamics (MD) simulations [G MD (r)] indicate that nearest-neighbor ion−ion interactions in the [PGA][TFSA] and [GA][TFSA] are comparable to those in imidazolium-based IL. Conversely, these are appreciably weakened at the second-and third-neighbors and thus less structured in the long range (r > 12 Å) and very different from the highly ordered imidazolium IL. The atom−atom pair correlation function derived from the MD simulations disclose that at a local scale, specific interactions are absent, with only an electrostatic interaction in the [PGA][TFSA], whereas the GA cations interact with TFSA anions via hydrogen bonding of diol groups in the GA and O atoms in the TFSA. No hydrogen bonding group within the PGA cation leads to weak ion-hydration resulting in a phase separation of [PGA][TFSA] and water; in contrast, the GA cations are easily hydrogen-bonded with water molecules to be miscible in aqueous solutions.

Prediction of self‐diffusion coefficients of chemically diverse pure liquids by all‐atom molecular dynamics simulations

“…Production MD runs of the self-diffusion coefficients in the NPT ensemble were started from the equilibrated simulation systems and continued at the temperature of interest. Theoretically, the selfdiffusion coefficient is accurately calculated based on Equation (2) and practically we can estimate self-diffusion coefficient from the slope of the MSD versus sufficient long lag time τ. 43 In this study, we divided the database into the two sets of highly diffusive samples (with logarithmic experimental diffusion coefficients [m 2 /s] larger than À9.5) and lowly diffusive samples (the rest of the entire dataset) to set an appropriate simulation time of 40 ns for the former and 150 ns for the latter.…”

“…Liquid materials are ubiquitous in organisms, environments, and industries involving reactants, solvents, and other functional entities. The diffusion of molecules in liquids has attracted considerable attention in the fields of fluid mechanics and liquid science, materials physics, chemical engineering, and theoretical chemistry 1–5 . The self‐diffusion coefficients of molecules in liquids are sensitive to the molecular structure, as well as the thermodynamic conditions such as temperature and pressure.…”

“…The diffusion of molecules in liquids has attracted considerable attention in the fields of fluid mechanics and liquid science, materials physics, chemical engineering, and theoretical chemistry. 1 , 2 , 3 , 4 , 5 The self‐diffusion coefficients of molecules in liquids are sensitive to the molecular structure, as well as the thermodynamic conditions such as temperature and pressure. Despite the increasing importance of the self‐diffusion coefficient in theoretical and applied chemistry, successful reports including a comprehensive prediction of the self‐diffusion coefficient of chemically diverse liquids under various conditions have been quite limited.…”

Strategy for Ultrafast Cathode Reaction in Magnesium-Ion Batteries Using BF4 Anion Based Dual-Salt Electrolyte Systems: A Case Study of FePO4

“…To obtain the detailed solvation structure around Mg 2+ at the atomic level, we conducted a combined analysis of the HEXTS measurement and MD simulation, as described in previous reports. 37,38,44 numbers estimated from the Raman measurements (N DMC = 4.5, N TFSA = 1.0). Thus, the solvation structure in the single-salt system was estimated to be [Mg(TFSA) 1 (DMC) 5 ] + (Figure 7d).…”

Preparation and Hydrophilicity/Lipophilicity of Solubility-Switchable Ionic Liquids

“…16 In our preliminary studies, we successfully found that the strategy worked well and developed new solubility-switchable ionic liquids. 17 As expected, the diol unit endowed good hydrophilicity to the ionic liquids mainly due to its hydrogen bonding, 18 and these ionic liquids were actually water-soluble. The acetal group is stable enough for pressure or temperature changes to some extent.…”