Mixtures Of Molecular Solvents Research Articles

Thermo-Reversible Cellulose Micro Phase-Separation in Mixtures of Methyltributylphosphonium Acetate and γ-Valerolactone or DMSO.

We have identified cellulose solvents, comprised of binary mixtures of molecular solvents and ionic liquids that rapidly dissolve cellulose to high concentration and show upper‐critical solution temperature (UCST)‐like thermodynamic behaviour ‐ upon cooling and micro phase‐separation to roughly spherical microparticle particle‐gel mixtures. This is a result of an entropy‐dominant process, controllable by changing temperature, with an overall exothermic regeneration step. However, the initial dissolution of cellulose in this system, from the majority cellulose I allomorph upon increasing temperature, is also exothermic. The mixtures essentially act as ‘thermo‐switchable’ gels. Upon initial dissolution and cooling, micro‐scaled spherical particles are formed, the formation onset and size of which are dependent on the presence of traces of water. Wide‐angle X‐ray scattering (WAXS) and 13C cross‐polarisation magic‐angle spinning (CP‐MAS) NMR spectroscopy have identified that the cellulose micro phase‐separates with no remaining cellulose I allomorph and eventually forms a proportion of the cellulose II allomorph after water washing and drying. The rheological properties of these solutions demonstrate the possibility of a new type of cellulose processing, whereby morphology can be influenced by changing temperature.

Insights on [BMIM][BF4] and [BMIM][PF6] ionic liquids and their binary mixtures with acetone and acetonitrile

The properties of ionic liquid plus acetone or acetonitrile mixtures were studied from the macro and microscopic levels by the measurement of relevant thermophysical properties and through molecular modelling studies. The liquid mixtures were considered in the whole composition range and analysed in terms of possible hydrogen bonding between the ions and ions with the molecular solvents. The reported results show how the large non-ideality of these systems stands on the high affinity of acetone and acetonitrile for the imidazolium hydrogen bond donor sites, which allow competition with the corresponding anions for these sites specially but not limited to molecular solvent rich mixtures. The reported results allow to quantify the relevance of hydrogen bonding for the properties of ionic liquid – molecular solvent mixtures, which can be fine-tuned through the amounts of cosolvent present in the mixture as a mechanism to control mixed fluids organization.

Comprehensive models for density prediction of ionic liquid + molecular solvent mixtures at different temperatures

ABSTRACTTo present comprehensive models for density prediction of the binary mixtures of ionic liquids (ILs), the density data for 193 sets of ionic liquid + molecular solvents were collected from the literature and were analysed by Jouyban-Acree and Jouyban-Acree-van’t Hoff and their combined version with Abraham solvation parameters. To check the capability of the trained models for density prediction, the ‘leave many out’ cross-validation method was used and the obtained overall % ARD were 3.7, 8.7, 4.1 and 8.5 for Jouyban-Acree, Jouyban-Acree-van’t Hoff, Jouyban-Acree–Abraham and Jouyban-Acree-van’t Hoff-Abraham models, respectively. It was concluded that all predictive models have the excellent accuracy for density prediction of the studied mixtures but the Jouyban-Acree and Jouyban-Acree-Abraham with lower %ARD are better than other models. However, the Jouyban-Acree-van’t Hoff–Abraham models may be preferred due to the lack of necessity of density data for components 1 and 2.

Viscosity prediction of ionic liquid + molecular solvent mixtures at various temperatures

To evaluate the ability of a combined form of the Jouyban-Acree model with the Abraham parameters, the viscosity data for 84 sets of ionic liquid + molecular solvent binary mixtures at various temperatures were predicted. Percent average relative deviations (%ARD) of the predicted and experimental values were calculated as an accuracy criterion and were obtained as 19.1 and 20.1 by considering the theoretical and experimental Abraham parameters, respectively. The collected data were also correlated using the Jouyban-Acree model, which is resulted in the overall %ARDs of 16.8 and 18.1 for back-calculated data by regarding the theoretical and experimental Abraham parameters, respectively. Moreover, to update the previously proposed global model, the earlier data were merged with the collected data from recent publications and total data sets were used to retrain the global Jouyban-Acree model by regarding the theoretical and experimental Abraham parameters. Comparing %ARD of the proposed model using correlated newly data and total (new and earlier) data sets show no statistically significant difference while there is a meaningful difference between calculations by considering the theoretical and experimental Abraham parameters. Moreover, to compare the capability of the Jouyban-Acree model for correlating viscosities of binary liquid mixtures, the overall %ARD were determined and compared to three selected models; Wilson, Katti and Chaudhary, and Eyring-NRTL. The order of the amount of obtained %ARD are Jouyban-Acree < Wilson < Katti and Chaudhary < Eyring-NRTL which is indicative of the suitability of Jouyban-Acree for correlation and prediction of the viscosity data for the binary liquid mixtures.

Correction to “Mathematical Representation of Viscosity of Ionic Liquid + Molecular Solvent Mixtures at Various Temperatures Using the Jouyban–Acree Model”

Correction to “Mathematical Representation of Viscosity of Ionic Liquid + Molecular Solvent Mixtures at Various Temperatures Using the Jouyban–Acree Model”

Standard partial molar volumes and viscosity B-coefficients of ionic liquids [Cnmim]Br (n = 4, 6, 8) in alcohols at 298.15 K

Volume and viscosity data of ionic liquid (IL)-molecular solvent mixtures are very important for the design of process engineering involving these mixtures. In this work, densities and viscosities for the binary solutions of [Cnmim]Br (n=4, 6, 8) ionic liquids with methanol, 1-propanol, and 1-pentanol have been determined at 298.15K as a function of IL concentrations. From these experimental data, apparent molar volumes, standard partial molar volumes, and viscosity B-coefficient of ILs were derived. The effect of the alkyl chain length in the imidazolium cation and properties of alcohol on the standard partial molar volumes of ILs and viscosity B-coefficient was discussed. In a given alcohol, the standard partial molar volumes of ILs and viscosity B-coefficient increase linearly with increasing alkyl chain length of ILs. For a given IL, unexpectedly, its standard partial molar volume in the three molecular solvents is not a constant, but increases in the order: 1-pentanol>1-propanol>methanol. The viscosity B-coefficients of a given IL in the alcohols also change in the same sequential order. These results suggest that the interactions between ILs and the alcohols increase with the decrease of alkyl chain length of the alcohols.

Investigation of Solvent Effects on the Reaction of 1-Fluoro-2,4-Dinitrobenzene with Aniline in Molecular-Molecular and Ionic Liquid–Molecular Solvent Mixtures

The solvent effects on the reaction of 1-fluoro-2,4-dinitrobenzene with aniline was studied in various compositions of molecular-molecular solvent mixtures and molecular solvent-2-hydroxyethylammonium formate mixtures as media containing an ionic liquid. A mounting trend with the mole fraction of water in aqueous solution of alcohols up to a maximum at a mole fraction of 0.9 with respect to water was found, but a mild decrease with the mole fraction of ethyl acetate in methanol–ethyl acetate mixtures. A similar increasing trend was observed with increasing methanol, ethanol, 2-propanol and dimethylsulfoxide content in the mixtures containing the ionic liquid. Solvent effect investigations based on linear free energy relationship confirm that polarity has a major effect in molecular-molecular solvent mixtures, whereas polarity and hydrogen–bond acceptor ability were the dominant factors on reaction rate in molecular-ionic solvent mixtures. A nonlinear free energy relationship based on the preferential solvation hypothesis showed differences between the microsphere solvation of the solute and the bulk composition of the solvents. In these mixtures, the intermediate of the reaction was preferentially solvated by the ionic liquid.

Specific spectroscopic behavior of Reichardt's betaine dye in binary mixtures of tetra-n-butylammonium glycinate and tetra-n-butylammonium l-alaninate with molecular solvents

The spectrophotometrical behavior of pyridinium N-phenolate betaine dye used as a solvatochromic indicator of solvent polarity is studied in binary mixtures of tetra-n-butylammonium glycinate and tetra-n-butylammonium l-alaninate with molecular solvents such as acetonitrile, ethyl acetate, and 1-butanol. This study shows that the solvent/solvent interactions, which cause preferential solvation of the dye solute, should not be established for studied amino acid-based ionic liquids with conventional molecular solvent mixtures. After addition of mole fraction of the ionic liquid, the intramolecular charge-transfer absorption spectrum of the betaine dye shows a dual peak structure. Variation of UV–Vis spectra demonstrates the existence of a relationship with the type of the molecular solvent. Molecular dynamic simulations showed clearly different compositions in the solvation shells of betaine dye.

Mathematical Representation of Viscosity of Ionic Liquid + Molecular Solvent Mixtures at Various Temperatures Using the Jouyban–Acree Model

The viscosity of room temperature ionic liquid + molecular solvents is correlated using the Jouyban–Acree model, and the accuracy of the model is evaluated using average relative deviations (ARD) of the calculated and experimental values. The overall ARD of 6.9 % was obtained for the proposed model where the overall ARD for a similar model from the literature was 22.4 %. The mean difference between ARDs of the models was statistically significant. Combined forms of the Jouyban–Acree model and the Abraham parameters were used for predicting the viscosity of the mixtures at various temperatures. The overall ARD for the investigated mixtures was 15.0 % when the experimental viscosity of the pure solvents was included. The ARD of the in silico version of the model was 20.7 %.

Effect of an Ionic Liquid Solvent on the Phase Behavior of Block Copolymers

The phase behavior of concentrated mixtures of block copolymers with an ionic liquid has been studied using a large series of block copolymers with varying molecular weight and volume fraction to gain a thorough understanding of the thermodynamics of self-assembly. The lyotropic phase behavior of mixtures of poly(styrene-block-2-vinylpyridine) (S2VP) copolymers with the ionic liquid imidazolium bis(trifluoromethane)sulfonimide ([Im][TFSI]) is reminiscent of block copolymer/selective molecular solvent mixtures, and ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed. Scaling analysis reveals that, in contrast to observations of block copolymer/molecular solvent mixtures, the interfacial area occupied by each S2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the S2VP copolymer with ionic liquid addition.

Part 2: Limiting apparent molar volume of organic and inorganic 1:1 electrolytes in (water + ethylammonium nitrate) mixtures at 298 K – Thermodynamic approach using Bahe–Varela pseudo-lattice theory

Values of partial molar volumes at infinite dilution of 9 inorganic and 4 organic 1:1 electrolytes have been determined in (water+ethylammonium nitrate) (EAN) binary at 298.15K throughout the composition scale. Our theoretical analysis shows that the values of partial molar volumes at infinite dilution of a solute in a binary are linked to those of the partial molar volumes of the components of mixed solvent. This applies to mixtures of molecular solvents as well as (water+ionic liquid) media. The use of the “pseudo-lattice theory” of Bahe recently supplemented Varela can be used for calculations and to obtain information about the interactions between 1:1 electrolytes as solutes at infinite dilution and their concentrated saline environment. We show that the “pseudo-lattice theory” allows accurate description of the behaviours of symmetrical tetraalkylammoniums bromide between the infinitely dilute state and concentrations higher than 2mol·L−1.

New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid–molecular solvent mixtures

The low vapor pressure and the versatility of the physico-chemical properties of ionic liquids make them really attractive as an alternative for conventional molecular solvents. The knowledge of their physico-chemical properties (viscosity, conductivity, miscibility with organic solvents and anion–cation interactions) has appeared mandatory for better targeting their applications, although it is generally still lacking or incomplete. This work promotes capillary electrophoresis instrumentation as an integrated apparatus for measurement of viscosity, conductivity and absorbance of pure ionic liquids and ionic liquid–molecular solvent mixtures. Compared to current conventional techniques, the assets of this instrumentation for this purpose are the combined availability of a pressure delivery system, power supply, diode array absorbance detector and thermoregulation device, allowing unattended, automatic and easy operation, involving minimum sample handling. Most importantly, the required sample volume can be reduced to about 50 μL, making this protocol very cost-effective. A protocol was optimized with respect to time, sample consumption and data reliability for the determination of these physico-chemical parameters. Ionic liquids selected for method development and validation differed in the nature of their cation (butyl- and ethyl-methylimidazolium) and anion (trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide). Various molecular solvents were mixed with these ionic liquids (acetonitrile, methanol, dimethylformamide and trifluoroethanol) and the same physico-chemical properties were determined by optimized methods. The knowledge of these data should be of great support in various application areas, including the development of new separation media for capillary electrophoresis and chromatographic techniques.