Fractional Walden Rule Research Articles

Decoupling Segmental Dynamics and Ionic Transport for Superionic Anhydrous Proton Conductors of Polyoxometalate-poly(ethylene glycol) Nanocomposites.

Superionic anhydrous proton conductors can be obtained from the complexation of nanoscale polyoxometalates (POMs) and poly(ethylene glycol) (PEG) in the "polymer in salt" regime. The reduced energy barrier of H+ hopping is facilitated from the increased H+ concentration and shortened inter-POM distances. POMs with identical structure/size (≈1nm) but different charge densities are complexed with PEG, respectively, with concentrations ranging from 10 to 60 % wt. Increasing trends of viscosities can be observed with the rising charge densities of POMs due to the increasing confinement strength on PEG substrate from POMs. Fractional Walden rule is further applied to analyze the viscosity and proton conductivity correlations, and microscopic mechanisms of proton conduction for PEG-POM nanocomposites are revealed: 1) ion transport is highly associated with polymer chain dynamic for POMs concentrations ranging from 10 to 30 % wt.; 2) ionic conduction is largely decoupled from chain dynamic of polymer matrix for concentrations ranging from 40 to 60 % wt. with Walden plots shifted to the superionic regime. The decoupling of proton transport from polymer segment dynamics allows the simultaneous enhancements of the nanocomposites' mechanical properties and proton conductions, providing guidelines for the rational design of anhydrous proton conductors with integrated functionalities.

On the physical properties of mixtures of nitrate salts and protic ionic liquids

We report a systematic study of the effect of salt concentration and its cation valence on several equilibrium and transport properties of mixtures of the model protic ionic liquid ethylammonium nitrate with monovalent (LiNO3), divalent (Mg(NO3)2 and Ca(NO3)2), and trivalent (Al(NO3)3) salts. These properties, determined by appropriate experimental techniques, include density, sound velocity, refractive index, surface tension, conductivity and viscosity. Single-particle dynamics and radial distribution functions were also analyzed by means of molecular dynamics simulations. The temperature dependence of the conductivity was studied in the Vogel-Fulcher-Tammann framework, and we obtained effective activation energies, fragility indexes, and Vogel temperatures. In addition, we performed a high-temperature Arrhenius analysis and we calculated the activation energies of both conductivity and viscosity. Finally, the exponents of the fractional Walden rule for the different mixtures were obtained and the ionicities and fragilities of the systems were analyzed, proving that all the mixtures are subionic and fragile. The distortion of the network of hydrogen bonds characteristic of protic ionic liquids and the formation of long-lived anionic aggregates composed of the cations of the added salt and the nitrate anions in their first solvation shell were found to have a deep impact on the analyzed properties. The role of the surface charge density of the salt cations on the structure and transport properties of the solutions is detailedly analyzed and related to solvation of salt species in the polar nanoregions of the ionic liquid (nanostructured solvation).

Thermophysical and Transport Properties of the BaCl2-CsCl High Temperature Ionic Liquid Mixtures

High temperature ionic liquids (HTILs) densities and transport properties for mixtures BaCl2‑CsCl, x(BaCl2) = 0-1, have been studied as a function of composition and temperature. In terms of Arrhenius theory, the temperature correlation of all measured properties was made and discussed. Thermodynamic properties (isothermal compressibility, molecular volume, lattice energy, heat capacity, molar Gibbs energy, enthalpy and entropy) were derived for all the studied HTILs from experimental data. The viscosity isotherms show negative deviations from linearity, while conductivity isotherms have positive deviations which may be related to the formation of highly negative changed ion associated species. The evolution of the excess quantities: viscosity deviation (Δη), excess molar viscosity (ΔEη), excess molar conductivity (ΔEκ), show a very good parallelism. The linear behavior between conductivity and viscosity was determined using the fractional Walden rule and the average slope was found far from unity.

Phase equilibria and thermophysical properties of aqueous solutions of two bis(fluorosulfonyl)imide-based ionic liquids

Ionic liquids comprising bis(fluorosulfonyl)imide (FSI) anion have been recognized to be well suited for technological applications as solvent and electrolyte media. In this work, we thoroughly investigated the thermodynamic and transport behavior of binary aqueous systems of two hydrophobic FSI-based ionic liquids, namely [EMIM][FSI] and [BMPYR][FSI]. Systematic measurements of phase equilibria, density, viscosity, and electric conductivity were conducted, our aim being to provide truly reliable information that would substantially upgrade that existing in the literature. Employing DSC measurements on the neat ILs and dynamic measurements of freezing or cloud point temperatures as well as static solubility measurements for aqueous ILs, phase diagrams for both these systems over a 100 K window were established. Rather large solubilities of water in these ILs allow for measurements of various other properties in the homogeneous IL-rich region. Extensive data thus obtained on water activity in this region were correlated for each system simultaneously with the mutual liquid-liquid solubilities, using an extended SSF (Sum of Symmetrical Functions) equation. This global excess Gibbs energy model not only accurately captures all the VLE, LLE, and SLE data we determined experimentally, but also discloses an enthalpy-driven system energetics with hydrophobic hydration effects that are more pronounced in the case of [BMPYR][FSI]. The measurements of density, viscosity, and conductivity covering the systems from the neat ILs to those almost saturated with water gave positive excess volumes and negative viscosity deviations that rise and diminish, respectively, as T increases. The conductivity increases monotonously with increasing water content and temperature. Accurate functional representations were also established for the volumetric, viscosity, and conductivity data, capturing simultaneously their composition and temperature dependence. The linkage between conductivity and viscosity was further analyzed by means of the fractional Walden rule which provided excellent fits for both isopleths and isotherms and indicated comparatively weaker coupling for the [BMPYR][FSI] system and the direction of the isothermal composition changes. Finally, comparing the FSI ILs with their TFSI analogs, the former were found to be clearly less hydrophobic.

Translational and reorientational dynamics in deep eutectic solvents.

We performed rheological measurements of the typical deep eutectic solvents (DESs) glyceline, ethaline, and reline in a very broad temperature and dynamic range, extending from the low-viscosity to the high-viscosity supercooled-liquid regime. We find that the mechanical compliance spectra can be well described by the random free-energy barrier hopping model, while the dielectric spectra on the same materials involve significant contributions arising from reorientational dynamics. The temperature-dependent viscosity and structural relaxation time, revealing non-Arrhenius behavior typical for glassy freezing, are compared to the ionic dc conductivity and relaxation times determined by broadband dielectric spectroscopy. For glyceline and ethaline, we find essentially identical temperature dependences for all dynamic quantities. These findings point to a close coupling of the ionic and molecular translational and reorientational motions in these systems. However, for reline, the ionic charge transport appears decoupled from the structural and reorientational dynamics, following a fractional Walden rule. In particular, at low temperatures, the ionic conductivity in this DES is enhanced by about one decade compared to expectations based on the temperature dependence of the viscosity. The results for all three DESs can be understood without invoking a revolving-door mechanism previously considered as a possible charge-transport mechanism in DESs.

Fractional Walden rule for aprotic ionic liquids: Experimental verification over a wide range of temperatures and pressures

The Walden rule, revealing a universal conductivity-viscosity relationship, is considered as a useful tool to investigate the transport mechanism in ionic liquids (ILs). In this work, we constructed the Walden plots covering 10 orders of magnitude for two ILs: 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BMMIm][NTf2] and 1-butyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide [BMIm][BETI] using experimental viscosity data at pressures up to 950 MPa supplemented by high-pressure conductivity and density data. Moreover, the high-pressure viscosity data of studied ILs revealed an inflection point denoting a transition from slower to faster than exponential dependence of viscosity on pressure. Finally, we found that the experimental viscosity data conform to the thermodynamic density scaling idea for each IL, with the scaling parameter equal to the ratio of scaling exponent obtained for conductivity data to the slope of the Walden plot. Consequently, our results show a promising method to generate high-pressure viscosity data especially for highly viscous aprotic ionic liquids, which are technically impossible to measure.

Physicochemical and electrochemical properties of the (fluorosulfonyl)(trifluoromethylsulfonyl)amide ionic liquid for Na secondary batteries

In this study, thermal, physical, and electrochemical properties of the ionic liquid electrolyte system, Na[FTA]-[C3C1pyrr][FTA], (FTA‒ = (fluorosulfonyl) (trifluoromethylsulfonyl)amide and C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) have been investigated for Na secondary batteries. The asymmetric FTA‒ structure provides a wide liquid-phase temperature range, especially at low x(Na[FTA]) (x(Na[FTA]) = molar fraction of Na[FTA]) and low temperature range. Glass transition at 170–209 K is the only observed thermal behavior in the x(Na[FTA]) of 0.0–0.4. Temperature dependence of viscosity and ionic conductivity obeys the Vogel‒Tammann‒Fulcher equation, and the correlation between molar conductivity and viscosity follows the fractional Walden rule. The anodic potential limits are above 5 V vs. Na+/Na at 298 and 363 K. The noticeable effects of x(Na[FTA]) are observed in the electrochemical performance of Na metal and hard carbon electrodes. In both cases, a moderate concentration, x(Na[FTA]) of 0.2–0.3, enables favorable charge-discharge behavior. At 363 K, the discharge capacities of the hard carbon electrode at x(Na[FTA]) of 0.3 are 260 and 236 mAh g−1 at the current densities of 20 and 200 mA g−1, respectively. The optimum cycling performance occurs at x(Na[FTA]) = 0.3, providing satisfactory capacity retention and high average Coulombic efficiency.

Structure Effects on the Ionicity of Protic Ionic Liquids.

We report on the characterisation of 16 protic ionic liquids (PILs) prepared by neutralisation of primary or tertiary amines with a range of simple carboxylic acids, or salicylic acid. The extent of proton transfer was greater for simple primary amine ILs compared to tertiary amines. For the latter case, proton transfer was increased by providing a better solvation environment for the ions through the addition of a hydroxyl group, either on the tertiary amine, or by formation of PIL/molecular solvent mixtures. The library of PILs was characterised by differential scanning calorimetry and a range of transport properties (i. e. viscosity, conductivity and diffusivity) were measured. Using the (fractional) Walden rule, the conductivity and viscosity results were analysed with respect to their deviation from ideal behaviour. The validity of the Walden plot for PILs containing ions of varying sizes was also verified for a number of samples by directly measuring self-diffusion coefficients using pulsed-field gradient spin-echo (PGSE) NMR. Ionicity was found to decrease as the alkyl chain length and degree of branching of both the cations and anions was increased. These results aim to develop a better understanding of the relationship between PIL properties and structure, to help design ILs with optimal properties for applications.

The physicochemical properties of the deep eutectic solvents with triethanolamine as a major component

Different deep eutectic solvents (DESs) of triethanolamine (TEOA) and oxalic acid (OA), glacial acetic acid (AA), L-(+)-lactic acid (LA), oleic acid (OLA), glycerol (G), ethylene glycol (EG), propylene glycol (PEG), choline chloride (ChCl) or 1,3-dimethylurea (DMU) were prepared and characterized regarding their physicochemical (density, viscosity, electrical conductivity, refractive index, coefficient of volume expansion, molecular volume, lattice energy and heat capacity) properties over the temperature range of 293.15?363.15 K at 101.325 kPa. For all tested DESs, the density, viscosity and refractive index decreased with rising temperature, while the electrical conductivity increased. The temperature dependence of viscosity and electrical conductivity are described by the Vogel?Tamman?Fulcher equations. The viscosity and molar conductivity, which exhibited a linear behaviour, were correlated by the fractional Walden rule. Besides, the Fourier transform infrared spectroscopy (FTIR) was used to study the functional groups of these DESs while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) provided the information about their stability. The tested DESs of TEOA possess desirable properties for use in various industrial processes, such as extractions, separations, chemical technology and biotechnology.

Influence of Wax Precipitation on the Impedance Spectroscopy of Waxy Oils

Impedance spectroscopy (IS) is a widely used nondestructive and high-throughput experimental technique for the characterization of electrical properties of materials. In the petroleum industry, IS is frequently employed to determine the electrical properties of asphaltenes and resins. The electrical properties of waxy crude oils, which correlate significantly with the flowability, however, have received little to no attention in the existing investigations. In this work, we inspected the influence of wax precipitation on IS of waxy crude oil for the first time. The investigation was carried out in a frequency range of 2 × 10–1 to 2 × 104 Hz and a temperature range of 5–60 °C. It was discovered that the Nyquist diagram representing the electrical response of waxy oil evolves from one semicircle to two semicircles as wax molecules precipitate at temperatures below the wax appearance temperature. IS of waxy crude oil can be reproduced by an equivalent circuit model composed of two serially connected constant phase element-ideal resistance combinations (Rbulk|Qbulk – Rwax|Qwax). It was found that the resistor-like contribution from wax in the equivalent circuit model, Rwax, increases with the amount of precipitated wax, whereas the capacitor-like contribution in the equivalent circuit model, Qwax, decreases with the amount of precipitated wax. Furthermore, the flow property of waxy oil, such as viscosity, can be related to the conductivity according to the fractional Walden rule. The entire viscosity–conductivity relationship can be divided into three regions, and each segment of the relationship can be fitted by the fractional Walden rule.

Mono- Vs. Di-Valent Solvated Cations Studied By Raman Spectroscopy

Raman spectroscopy is a powerful tool to study molecular level interactions in e.g. battery electrolytes. As cations and solvents interact, this affects the ion-pair formation and the nature of the solvation shells, which both are key factors affecting solution equilibria and ion transport. While Raman spectroscopy has been extensively used to study lithium-ion battery (LIB) electrolytes, studies on alternative battery technology electrolytes are scarce. Most concern sodium-ion batteries (SIB) and the interpretations are eased by the chemical similarity of Li and Na — both being monovalent. For divalent battery technologies such as Ca and Mg the differences in cation solvation can be expected to be larger, due to the fundamental differences between mono- and divalent ions, and prevents the full application of LIB electrolyte know-how and hence calls for further studies. The recently unveiled calcium battery technology [1] is today limited in scope of electrolytes, basically two compositions dominate [1, 2]. The lack of variety and understanding considerably slows down the Ca battery development, why more in depth analysis of the Ca2+ solvation is called for, to highlight issues hindering fast cation transport within the electrolytes. Here monovalent electrolytes composed of NaPF6 or NaTFSI dissolved in mixtures of ethylene carbonate (EC) and dimethyl carbonate (DMC), i.e. EC:DMC (1:1) were investigated for concentrations ranging from 0.3–1.0 M. They were selected based on the similarities with common LIB electrolytes either commercialized or extensively studied at the laboratory scale [3]. Divalent electrolytes composed of Ca(TFSI)2 and Ca(BF4)2 dissolved in a mixture of ethylene carbonate (EC) and propylene carbonate (PC), i.e. EC:PC (1:1) were chosen for their compatibility with available Ca electrodes [4, 5]. Both Raman spectroscopy and density functional theory calculations were employed to understand quantitatively how the speciation and solvation differ between these monovalent and divalent electrolytes, and ultimately how it could affect ion transport within both electrolytes and electrodes. In addition to the ion conductivities also the viscosities were measured to enable us to apply the fractional Walden rule [6] and qualitatively estimate the ion-pairing as function of both temperature and salt concentration. We observe that the solvation shell configurations change with the salt concentration for both multivalent and divalent formulations; the sizes of the divalent cationic complexes are nearly twice as large as the monovalent but the solvent coordination order is similar; EC tends to predominantly coordinate the cations, followed by PC or DMC. Finally, the Walden plots indicate that formation of contact ion-pairs (CIP) and/or aggregates (AGG) may be more likely for the BF4 based electrolytes, independent of the nature of the cation.

Ionic Transport and Speciation of Lithium Salts in Glymes: Experimental and Theoretical Results for Electrolytes of Interest for Lithium-Air Batteries.

Glycol ethers, or glymes, have been recognized as good candidates as solvents for lithium–air batteries because they exhibit relatively good stability in the presence of superoxide radicals. Diglyme (bis(2-methoxy-ethyl)ether), in spite of its low donor number, has been found to promote the solution mechanism for the formation of Li2O2 during the discharge reaction, leading to large deposits, that is, high capacities. It has been suggested that lithium salt association in these types of solvents could be responsible for this behavior. Thus, the knowledge of the speciation and transport behavior of lithium salts in these types of solvents is relevant for the optimization of the lithium–air battery performance. In this work, a comprehensive study of lithium trifluoromethanesulfonate (LiTf) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1,2-di-methoxyethane (DME) and diglyme, over a wide range of concentrations, have been performed. Consistent ion pairs and triplet ions formation constants have been obtained by resorting to well-known equations that describe the concentration dependence of the molar conductivities in highly associated electrolytes, and we found that the system LiTf/DME would be the best to promote bulky Li2O2 deposits. Unexpected differences are observed for the association constants of LiTf and, to a lesser extent, for LiTFSI, in DME and diglyme, whose dielectric constants are similar. Molecular dynamics (MD) simulations allowed us to rationalize these differences in terms of the competing interactions of the O-sites of the ethers and the SOx groups of the corresponding anions with Li+ ion. The limiting Li+ diffusivity derived from the fractional Walden rule agrees quite well with those obtained from MD simulations, when solvent viscosity is conveniently rescaled.

Diglyme Based Electrolytes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are currently being considered for large-scale energy storage. Optimization of SIB electrolytes is, however, still largely lacking. Here we exhaustively evaluate NaPF6 in diglyme as an electrolyte of choice, via both physicochemical properties and extensive electrochemical tests including half as well as full cells. Fundamentally, the ionic conductivity is found to be quite comparable to carbonate based electrolytes and to obey the fractional Walden rule with viscosity. We find Na metal to work well as a reference electrode and the electrochemical stability, evaluated potentiostatically for various electrodes and corroborated by DFT calculations, to be satisfactory in the entire voltage range 0–4.4 V. Galvanostatic cycling at C/10 of half and full cells using Na3V2(PO4)3 (NVP) or Na3V2(PO4)2F3 (NVPF) as cathodes and hard carbon (HC) as anodes indicates rapid capacity fading in cells with HC anodes, possibly originating in a lack of a stable SEI or by trapping of sodium. Aiming ...

The Temperature Effect on the Transport Properties of 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids

The temperature dependences of specific and equivalent conductivities, viscosity, density, and crystallization temperature are determined for three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C n MeIm] [Tf2N], n = 2, 3, 4) ionic liquids saturated with water vapor at room temperature. It is established that in the area of positive temperatures, the relationship between viscosity and conductivity obeys the fractional Walden rule with exponents of 0.97, 0.92, and 0.92 for ionic liquids with ethyl-, propyl-, butylradicals, respectively. The temperature dependences of conductivity and viscosity are approximated using the Vogel–Fulcher–Tammann equation (R2 > 0.999), and ideal glass transition temperatures T0 are calculated for the investigated liquids. The obtained values of T0 depend largely on the chosen range of temperatures. It is shown that [C2MeIm][Tf2N] occupies a separate position with regard to [C3MeIm][Tf2N] and [C4MeIm][Tf2N].

Transport properties of protic and aprotic guanidinium ionic liquids.

Ionic liquids (ILs) are a promising class of solvents, functional fluids and electrolytes that are of high interest for both basic as well as applied research. For further fundamental understanding of ILs and a successful implementation in technical processes, a deeper insight into transport properties and their interrelations is of particular importance. In this contribution we synthesised a series of mostly novel protic and aprotic ILs based on the tetramethylguanidinium (TMG) cation that is a derivative of the superbase guanidine. Different substitution patterns and anions from acids with broadly varied pKa values were investigated. We measured general properties, such as thermal transitions and densities of these ILs, as well as their transport quantities by means of rheology, impedance spectroscopy and NMR diffusometry. Different models for the correlation of the transport properties, namely the Nernst–Einstein, Walden and Stokes–Einstein–Sutherland relations were applied. The deviation from ideal behaviour of fully dissociated electrolytes, often termed as ionicity, was quantified by the reciprocal Haven ratio, fractional Walden rule and ionicity obtained from the Walden plot. Velocity cross-correlation coefficients were calculated to gain further insight into the correlation between ion movements. Both protic and aprotic TMG ILs show transport properties comparable to other ILs with similar molecular weight and high ionicity values especially in contrast to other protic ILs. Lowest ionicity values were found for the protic ILs with smallest ΔpKa values between constituting acid and base. This can either be explained by stronger hydrogen bonding between cation and anion or lower anti-correlations between the oppositely charged ions. These results aim to provide insight into the properties of this interesting cations class and a deeper understanding of the transport properties of ILs and their interrelations in general.

Thermal, Physical, and Electrochemical Properties of Li[N(SO2F)2]-[1-Ethyl-3-methylimidazolium][N(SO2F)2] Ionic Liquid Electrolytes for Li Secondary Batteries Operated at Room and Intermediate Temperatures

The Li[FSA]-[C2C1im][FSA] (FSA–: bis(fluorosulfonyl)amide and C2C1im+: 1-ethyl-3-methylimidazolium) ionic liquids have been studied as electrolytes for Li secondary batteries, though their thermal, physical, and electrochemical properties have not been systematically characterized. In this study, the thermal and transport properties of Li[FSA]-[C2C1im][FSA] ionic liquids as a function of the Li[FSA] molar fraction and temperature, in view of their operation at both room and intermediate temperatures. Differential scanning calorimetric analysis revealed that this system has a wide liquid-phase temperature range from Li[FSA] fractions of 0.0 to 0.4 and indicated the existence of the Li[C2C1im][FSA]2 line compound. Single-crystal X-ray diffraction analysis was used to determine the crystal structure of Li[C2C1im][FSA]2, which consists of Li+ octahedrally coordinated by six O atoms originating from four FSA– anions. The temperature dependences of the viscosity and ionic conductivity were fitted by the Vogel–Tammann–Fulcher equation, and the viscosity and molar ionic conductivity were connected by the fractional Walden rule. Lithium–metal deposition/dissolution efficiency decreased with increasing measurement temperature and decreasing Li[FSA] fraction. Aluminum corrosion at positive potentials was investigated by a potential step method, which revealed that the stability of an aluminum electrode was improved at high Li[FSA] fractions at 298 K, and the corrosion-limit potential decreased at elevated temperatures.

Transport properties and ionicity of phosphonium ionic liquids.

Ionic liquids (ILs) are promising electrolytes and many efforts have been made in basic scientific research as well as in applied research. In this contribution, we synthesised a variety of partly novel phosphonium ILs with different anions as well as with different compositions and lengths of the side chains of the cations. We measured a variety of their important transport properties such as viscosity, conductivity and diffusivity by means of stress-controlled rheology, impedance spectroscopy and PFGSTE NMR diffusometry. The results are analysed with respect to different models for derivation from ideal behaviours such as the ionicity and the (fractional) Walden rule depending on their molecular structure. These models are well established in the literature and are herein applied to rarely investigated but promising phosphonium ILs, with a particular emphasis placed on the effect of ether side chains. In comparison, the models show a qualitative correlation but distinct deviation in the quantification especially in the temperature dependent values and with other IL systems. These results aim to facilitate a better understanding of the IL properties depending on the molecular composition and by this way help to choose the ILs with optimal properties for practical applications.

The physicochemical and thermodynamic properties of the choline chloride-based deep eutectic solvents

This paper reports the physicochemical (density, dynamic viscosity, electrical conductivity and refractive index) and the thermodynamic (thermal expansion coefficient, molecular volume, lattice energy and heat capacity) properties of several choline chloride (ChCl) based deep eutectic solvents (DESs), with 1:2 mole ratio, respectively: ChCl:propylene glycol, ChCl:1,3-dimethylurea and ChCl:thiourea, at atmospheric pressure as a function of temperature over the range of 293.15?363.15 K. Their properties were also compared with those of some already characterized ChCl-based DESs, namely ChCl:ethylene glycol, ChCl:glycerol and ChCl:urea (1:2 mole ratio). Density, viscosity and refractive index of all DESs decrease with the increasing temperature while the electrical conductivity increases. Viscosity and conductivity of the tested DESs were fitted by both Arrhenius-type and Vogel?Tamman?Fulcher equations. The changes of molar enthalpy, entropy and Gibbs energy of activation, determined using the Eyring theory, demonstrated the interactional factor as predominant over the structural factor for all DES systems. The fractional Walden rule, used to correlate molar conductivity and viscosity, showed an excellent linear behaviour. It was shown that ChCl:propylene glycol DES had properties similar to ChCl:ethylene glycol and ChCl:glycerol DESs. However, the properties (density, viscosity and electrical conductivity) of ChCl:1,3-dimethylurea and ChCl: :thiourea DESs were inferior to those of the ChCl:urea DES.

Investigation of Ternary Mixtures Containing 1-Ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)azanide, Ethylene Carbonate and Lithium Bis(trifluoromethanesulfonyl)azanide.

Temperature-dependent viscosity, conductivity and density data of ternary mixtures containing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)azanide (EMIM-TFSA), ethylene carbonate (EC), and lithium bis(trifluoromethanesulfonyl)azanide (Li-TFSA) were determined at atmospheric pressure in the temperature range of 20 to 80 °C. Differential scanning calorimetry (DSC) measurements were performed to characterize phase conditions of the mixtures in a temperature range of −120 to +100 °C. The viscosity data were fitted according to the Vogel-Fulcher-Tammann-Hesse (VFTH) equation and analyzed with the help of the fractional Walden rule. In this study, fundamental physicochemical data about the mixtures are provided and discussed as a basis for structure-property relationship calculations and for potential use of those mixtures as electrolytes for various applications.

Citric acid-based deep eutectic solvents: Physical properties and their use as cosolvents in sulphuric acid-catalysed ethanolysis of oleic acid

Deep eutectic solvents (DESs) are noted to be green ionic liquid (IL) analogues, and their many favourable properties made them interesting for the scientific community. In this study, two novel DESs of citric acid with the monosaccharides D-glucose or D-fructose (1:1 molar ratio) were prepared and characterized. At the atmospheric pressure, the density, the dynamic viscosity, and the electrical conductivity of these eutectic solvents were measured and analysed as the function of temperature in the practical temperature range of 293.15-363.15 K. Arrhenius theory was employed for understanding the transport phenomena in these DESs. By using the experimental data, some important properties were calculated such as molecular volume, lattice energy, heat capacity, molar Gibbs energy, enthalpy and entropy of activation of viscous flow for the synthesized DESs. The fractional Walden rule was employed to establish the relationship between molar conductivity and viscosity, which proved an excellent linear behaviour. Finally, these DESs were tested as cosolvents in oleic acid (OA) ethanolysis. The investigated DESs possess many desirable properties, such as low vapour pressure, inflammability, biodegradability, and can be obtained from available renewable resources. These DESs showed to have the potential to be utilized for several industrial applications, like processing and separation of food constituents, pharmaceutical applications, and mediums for chemical reactions.