The densities and viscosities for the binary systems of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim][BF4], with the molecular solvents: dimethylsulfoxide (DMSO) and ethylene glycol (EG), were measured over the whole concentration range in the temperature range from (293.15 to 353.15) K by using an Anton Paar DMA 4500 densimeter and an Anton Paar AMVn measuring assembly, respectively. The temperature dependence of density and dynamic viscosity both for pure [Bmim][BF4] and its binary mixtures can be described by an empirical linear equation and by the Vogel-Fucher-Tammann (VFT) equation, respectively. The excess molar volumes, V E, were calculated by using the measured experimental data and fitted to a Redlich−Kister equation. These values are negative for the [Bmim][BF4] + DMSO system and positive for the [Bmim][BF4] + EG system over the whole composition range at investigated temperatures. The V E results have been analyzed using the Prigogine−Flory−Patterson (PFP) theory, which can explain the volumetric behavior of the investigated binary mixtures.

The knowledge and prediction of physicochemical properties of binary liquid mixtures is of great importance for understanding intermolecular interactions. Viscosities (η) have been investigated by using density (ρ) and kinematic viscosity (ν) measurements for 1,4-dioxane + water (D-W) mixtures over the entire range of mole fractions under atmospheric pressure, at 311.15, 316.15 and 320.15 K, in order to increase the studied temperatures range available from the literature and to improve the investigations. The viscosity Arrhenius activation energy of 1,4-dioxane + water mixtures was calculated from the present experimental viscosity measurements, and those presented in a previous work at only four temperatures, and for three temperatures in the present work, over the entire range of composition in the temperatures range from 293.15 to 323.15 K. Based on the partial molar activation energy from the Arrhenius equation for viscosity, interactions between water and 1,4-dioxane molecules are discussed. Comparison between some reduced Redlich-Kister functions covering the composition domain shows the existence of two distinct behaviors.

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This work presents density and dynamic viscosity data for the pure ionic liquid, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, [Bmmim] [BF 4 ], and its binary mixtures with the highly polar solvents dimethylsulfoxide (DMSO) and acetonitrile (ACN), over the entire range of composition and temperatures from (298.15 to 353.15) K at atmospheric pressure. The properties have been represented with temperature by specific equations, both for pure [Bmmim] [BF 4 ] and its binary mixtures. Therefore, an empirical linear equation was used for density variation and for viscosity, the Vogel−Fucher−Tammann (VFT) equation. From the density data the excess molar volume, V E , apparent molar volume, V ϕi , and partial molar volume, V̅ mi , as well as thermal expansion coefficient, α p , have been evaluated. Moreover, the excess molar volume was fitted to the Redlich− Kister polynomial equation, and its variation with composition has been qualitatively discussed in terms of interaction and structural factors. ■ INTRODUCTIONIonic liquids (ILs) are a class of substances extensively studied by the scientific community because of their interesting properties such as a negligible vapor pressure, low melting point, suitable viscosity, high conductivity, wide electrochemical windows, and high stability, which makes them suitable for a diversity of applications, especially as solvents. 1−4 These solvents are called "green" because of their low vapor pressure and nonflammability.One of the most studied ILs are 1,3-alkyl-substituted imidazolium-based, whose properties can be modified by changing cation/anion combinations. Some of these properties can also be changed by replacing the hydrogen atom at position 2 of the imidazole ring with alkyl substituents. 5−7 The trialkylsubstituted imidazolium-based ILs are considered by some researcher groups to be promising material for electrochemical applications, 8−11 inorganic synthesis, 12 or enzymatic catalysis. 13 Our interest for the trialkyl-substituted imidazolium-based ILs is on the one hand to study the physicochemical properties of solvent systems with ILs that can be used as new media in the synthesis of different metal oxide nanostructures; in this sense we have already studied three 1-alkyl-3-methylimidazolium tetrafluoroborate ILs. 19,20 On the other hand the binary mixtures of such trialkyl-substituted imidazolium-based ILs with organic solvents are interesting from the fundamental research point of view for understanding the relation between structure and mixture properties, especially by comparing them with corresponding dialkyl-substituted mixtures.Therefore, in this paper we extended our studies on physicochemical properties of dialkyl-substituted 19,20 to trialkyl-substituted imidazolium ILs systems, with the same organic solvents, dimethylsulfoxide (DMSO) and acetonitrile (ACN). Also, it was interesting to comparatively discuss the volumetric behavior of these systems and to analyze the influence of cation nature or solvent type on the reported properties.The studies on th...

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This work reports the experimental results of the densities, viscosities and refractive indices between 298.15 and 323.15 K of the dimethyl sulfoxide + + o-xylene system over the entire composition range of the mixtures. The excess molar volumes (V E ), viscosity deviations ( ν), excess Gibbs energy of activation of viscous flow (G * E ) and deviations in the refraction ( R) were calculated from the experimental data; all the computed quantities were fitted to the Redlich-Kister equation. The system exhibits moderate negative values for the investigated excess properties. The resulting excess functions were interpreted in structural and interactional terms. From the experimental data, the thermodynamic functions of the activation of viscous flow were estimated. The viscosity data were correlated with several semi-empirical equations. The two-parameter McAllister equation can give very good results.

The densities have been determined for the binary systems of ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate, [Emim] [BF 4 ] and 1-hexyl-3-methylimidazolium tetrafluoroborate, [Hmim] [BF 4 ], with the molecular solvents dimethyl sulfoxide (DMSO) and acetonitrile (ACN) at atmospheric pressure over the entire range of composition and temperatures from (298.15 to 353.15) K. From experimental densities, the excess molar volumes, V E , were calculated and fitted to a Redlich−Kister equation. Moreover, the V E results have been discussed in terms of the Prigogine−Flory−Patterson (PFP) theory. The V E variation was interpreted in terms of intermolecular interactions and structural effects on mixing. ■ INTRODUCTIONRoom-temperature ionic liquids (ILs) have caught the attention of researchers due to their extraordinary properties as roomtemperature molten salts. Some of these, like negligible vapor pressure, wide liquid range, and an ionic conductivity−viscosity ratio, make them potential green solvents or reaction media for many applications. 1−4 Generally, to design an industrial process involving ILs, it is important to know their physicochemical properties. One attraction of ILs is the possibility to obtain the desired properties by modifying the nature and size of the cations and anions, and a strategy in the application of ILs is to use mixtures of IL + organic (or inorganic) solvent to generate the targeted properties. In addition, by knowing the excess properties we can better understand the structure−property relation, making it easier choosing an appropriate IL. Therefore, IL + solvent mixtures have received growing attention in the past years.Up to now, the most investigated ionic liquids are those containing 1,3-dialkylimidazolium cations. In this context, the thermophysical properties of binary systems of 1-alkyl-3-methylimodazolium tetrafluoroborates with polar organic solvents, like dimethyl sulfoxide and acetonitrile, have been studied in literature. 5−10 As a continuation of our studies involving physicochemical properties of pure 1-alkyl-3-methylimodazolium tetrafluoroborates and its mixtures with traditional organic solvents, 11 we report here the densities of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-hexyl-3-methylimidazolium tetrafluoroborate and their binary mixtures with dimethyl sulfoxide (DMSO) and acetonitrile (ACN) from (293.15 to 353.15) K over the whole composition range.To our best knowledge, for the binary systems of both studied ionic liquids with ACN only density data is reported at temperature of 298.15 K 5 ; for the other two studied systems no literature data concerning volumetric properties are available. ■ EXPERIMENTAL SECTIONMaterials. We used the reagents: 1-ethyl-3-methylimidazolium tetrafluoroborate (mass fraction > 0.98) from Sigma

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