Density, Speed of Sound, and Viscosity of Some Binary and Ternary Aqueous Polymer Solutions at Different Temperatures

Density, speed of sound and viscosity measurements at (288.15, 293.15, 298.15, 303.15 and 308.15) K were carried out on several binary (water + polymer) and ternary (water + polymer (1) + polymer (2)) systems. Polymers were polyethylene glycol 600 (PEG600), polyethylene glycol 10000 (PEG10000), polypropylene glycol 400 (PPG400), polyethylene glycol dimethyl ether 250 (PEGDME250), and polyvinylpyrrolidone 10000 (PVP10000). The measured density and speed of sound data were used to determine the excess specific volume, isentropic compressibility, and isentropic compressibility increment of the investigated solutions as well as the apparent specific volume, limiting apparent specific volume, limiting apparent specific expansibility, apparent isentropic compressibility, and limiting apparent isentropic compressibility of each polymer in the aqueous solutions of 1 % and 3 % (w/w) other investigated polymers. The intrinsic viscosities for the investigated binary and ternary systems were calculated from the experimental viscosity data. Finally, the ability of polymer (1) in varying the volumetric, compressibility, and viscometric properties of polymer (2) in aqueous solutions was discussed on the basis of the polymer–water and polymer (1)–polymer (2) interactions

Evaluation of the Capability of Ionic Liquid–Amino Acid Aqueous Systems for the Formation of Aqueous Biphasic Systems and Their Applications in Extraction

To obtain further experimental evidence for a better understanding of the molecular mechanisms responsible for the soluting-out effect phenomena in ternary systems composed of an ionic liquid (IL), amino acid, and water, systematic studies on the vapor–liquid, liquid–liquid, and solid–liquid equilibrium behavior of aqueous solutions of several ILs were carried out in the presence of a range of amino acids. Water activities for binary and ternary aqueous solutions containing 1-butyl-3-methylimidazolium chloride, [C₄mim]­Cl, 1-hexyl-3-methylimidazolium chloride, [C₆mim]­Cl, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C₄mim]­[CF₃SO₃], l-Ser, Gly, Ala, and l-Pro were measured using both vapor pressure osmometry and isopiestic methods. All of the ternary IL + amino acid + water systems show negative deviations from semi-ideal behavior and therefore soluting-out effects have been observed in these systems. In the case of the [C₄mim]­[CF₃SO₃] + amino acids aqueous systems, the IL is soluted-out by the amino acids and the soluting-out effect appears by aqueous biphasic system formation. For these systems, the phase diagram and partition coefficient of caffeine were measured at 298.15 K. However, for the [C₄mim]Cl and [C₆mim]Cl containing systems, the amino acids are soluted-out by the ILs and the soluting-out effect appears by precipitation of the amino acids from the solution, and the solubilities of the amino acids in the aqueous solutions decrease in the presence of [C₄mim]Cl and [C₆mim]­Cl

Vapor Pressure Osmometry, Volumetry, and Compressibility Properties for Solutions of Several Imidazolium Based Ionic Liquids in (Glycine + Water) Solutions

In this study, the effect of glycine on the thermodynamic properties of aqueous solutions containing ionic liquids 1-butyl-3-methylimidazolium chloride, [C₄mim]­Cl, 1-hexyl-3-methylimidazolium chloride, [C₆mim]­Cl, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C₄mim]­[CF₃SO₃], has been studied. For this purpose, first with help of the vapor pressure osmometery (VPO) method the water activity measurements have been performed on the ternary aqueous systems of (glycine + [C₄mim]­Cl, [C₆mim]­Cl, and [C₄mim]­[CF₃SO₃]) at <i>T</i> = 308.15 K. The influence of the IL nature on the vapor–liquid equilibria behavior of the investigated systems has been studied. The VPO measurements of these solutions show that due to the unfavorable IL-glycine interactions, the negative deviations from the semi-ideal state and in conclude the soluting-out effects have been observed in these solutions. The soluting-out phenomena appears by aqueous biphasic system formation in the case of aqueous [C₄mim]­[CF₃SO₃] + glycine system and precipitation of the glycine from the solution in the case of ternary [C₄mim]­Cl/[C₆mim]Cl + glycine + water systems. In the second part of this work, density and sound velocity of solutions of the ILs in pure water and aqueous glycine solutions have been measured at four different temperatures. These data were used to obtain the apparent molar volume, <i>V</i>_ϕ, isentropic compressibility, <i>K</i>_ϕ, and those in the infinite dilution

Vapor Pressure Osmometry Studies of Aqueous Ionic Liquid–Carbohydrate Systems

Precise vapor pressure osmometry (VPO) measurements at 308.15 K were conducted for solutions of three ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]­[BF₄]), 1-butyl-3-methylimidazolium bromide ([Bmim]­[Br]), and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]­[HSO₄]), in aqueous solutions of three carbohydrates, sucrose, maltose, and maltitol, as well as for solutions of the carbohydrates in aqueous solutions of these ILs. Because of the unfavorable IL–carbohydrate interactions, all the investigated IL + carbohydrates aqueous systems show the soluting-out effect and vapor–liquid equilibria behavior of these systems in the monophasic region show the negative deviation from the semi-ideal behavior (<i>a</i>_w + 1 < <i>a</i>_wIL° + <i>a</i>_wC° and Δ<i>p</i> < Δ<i>p</i>_IL° + Δ<i>p</i>_C°). For a certain carbohydrate and at the same molality of IL, the magnitude of the departures for the investigated ILs follows the order: [Bmim]­[BF₄] > [Bmim]­[HSO₄] ≫ [Bmim]­[Br]. In the case of [Bmim]­[BF₄]/carbohydrate aqueous systems, which have a phase separation capability, the soluting-out power of the carbohydrates on [Bmim]­[BF₄] in aqueous solutions (or negative deviation from the semi-ideal behavior) reduced by decreasing the hydrophilicity of the carbohydrates. Aqueous [Bmim]­[Br]/carbohydrate and [Bmim]­[HSO₄]/carbohydrate systems are unable to form the ABS, and the soluting-out effect of the ILs on the aqueous carbohydrate solutions appears in the form of precipitation of sugars from the aqueous solutions

Salting-In and Salting-Out of Water-Soluble Polymers in Aqueous Salt Solutions

To obtain further experimental evidence for the mechanisms of the salting effect produced by the addition of salting-out or sating-in inducing electrolytes to aqueous solutions of water-soluble polymers, systematic studies on the vapor–liquid equilibria and liquid–liquid equilibria of aqueous solutions of several polymers are performed in the presence of a large series of electrolytes. Polymers are polyethylene glycol 400 (PEG400), polyethylene glycol dimethyl ether 250 (PEGDME250), polyethylene glycol dimethyl ether 2000 (PEGDME2000), and polypropylene glycol 400 (PPG400), and the investigated electrolytes are KCl, NH₄Cl, MgCl₂, (CH₃)₄NCl, NaCl, NaNO₃, Na₂CO₃, Na₂SO₄, and Na₃Cit (tri-sodium citrate). Aqueous solutions of PPG400 form aqueous two-phase systems with all the investigated salts; however, other investigated polymers form aqueous two-phase systems only with Na₂CO₃, Na₂SO₄, and Na₃Cit. A relation was found between the salting-out or sating-in effects of electrolyte on the polymer aqueous solutions and the slopes of the constant water activity lines of ternary polymer–salt aqueous solutions, so that, in the case of the salting-out effect, the constant water activity lines had a concave slope, but in the case of the salting-in effects, the constant water activity lines had a convex slope. The effect of temperature, anion of electrolyte, cation of electrolyte, and type and molar mass of polymers were studied and the results interpreted in terms of the solute–water and solute–solute interactions. The salting-out effect results from the formation of ion (specially anion)–water hydration complexes, which, in turn, decreases hydration, and hence, the solubility of the polymer and the salting-in effect results from a direct binding of the cations to the ether oxygens of the polymers

Isopiestic Investigations of the Interactions of Water-Soluble Polymers with Imidazolium-Based Ionic Liquids in Aqueous Solutions

To provide insight into the salting effects produced by the addition of hydrophilic ionic liquids to aqueous solutions of water-soluble polymers and to obtain a relation between the vapor–liquid and liquid–liquid equilibrium behavior of ionic liquid–polymer aqueous–biphasic systems, the isopiestic equilibrium molalities of some ternary ionic liquid–polymer–water systems in both the one- and two-phase areas together with the liquid–liquid equilibrium phase diagrams for systems capable of inducing phase separation were determined at 298.15 K. The polymers are poly­(ethylene glycol) 400 (PEG400), poly­(ethylene glycol) 2000 (PEG2000), poly­(ethylene glycol) 6000 (PEG6000), poly­(ethylene glycol) 10 000 (PEG10 000), poly­(propylene glycol) 400 (PPG400), and poly­(propylene glycol) 725 (PPG725), and the investigated ionic liquids are 1-butyl-3-methylimidazolium bromide ([C₄mim]­[Br]) and 1-butyl-3-methylimidazolium hydrogen sulfate ([C₄mim]­[HSO₄]). It was found that aqueous solutions of [C₄mim]­[HSO₄] form aqueous biphasic systems with PPG400 and PPG725 (salting-out effect); however, other investigated systems do not form aqueous biphasic systems (salting-in effect). A relationship was found between the salting-out and salting-in effects of ionic liquids on aqueous polymer solutions and the slopes of the constant water-activity lines for ternary ionic liquid–polymer aqueous solutions so that in the case of the salting-out effect the constant water-activity lines had a concave slope, but in the case of the salting-in effect the constant water-activity lines had a convex slope

Investigation of Amino Acid–Polymer Aqueous Biphasic Systems

Aiming at gathering further information to evaluate the recently proposed, mechanism of the salt effect in aqueous polymer solutions, experimental vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and volumetric-compressibility measurements were carried out for several polymer–amino acid aqueous systems. The constant water activity lines (obtained through the isopiestic method at 298.15 K) of aqueous polypropylene glycol 400 (PPG400) + alanine or glycine systems, which form aqueous biphasic systems (salting-out effect), have a concave and convex slope, respectively, in the one-phase and two-phase regions. However, all the investigated polyethylene glycols (PEG400, PEG2000, PEG6000, and PEG10000) do not form aqueous biphasic systems with alanine or glycine (salting-in effect) and their constant water activity lines have a convex slope. In the second part of this work, the apparent molar volume and isentropic compressibility of transfer of alanine and glycine from water to aqueous solutions of PEG200, PEG2000, PEG10000, and PPG400 were studied at different temperatures. The third part of this work is concerned with the determination of LLE phase diagrams for several ternary polymer–amino acid aqueous systems containing polymers PPG400 and PPG725 and amino acids alanine, glycine, serine, and proline at different temperatures. On the basis of the obtained cloud point values of aqueous solutions of PPG725 in the absence and presence of various amino acids, it was found that all the investigated amino acids have a salting-out effect on PPG725 in aqueous solutions and entropy is the driving force for biphasic formation

Toward an understanding of volumetric and isentropic compressibility behavior of imidazolium-based ionic liquids in aqueous polymer solutions

A systematic experimental density and sound velocity measurement was carried out for imidazolium-based ionic liquids (ILs) in pure water and in aqueous solutions of 0.03 w/w of water-miscible polymers with different structures and molar masses at T= (288.15, 293.15, 298.15, 303.15 and 308.15) K and p = 84.5 kPa. The ILs under investigation are 1-butyl-3-methylimidazolium hydrogen sulphate ([C4mim][HSO4]) and 1-butyl-3-methylimidazolium bromide ([C4mim]Br). The effects of temperature, polymer type, and IL anion type on the various volumetric and compressibility properties, such as apparent molar volume, isentropic compressibility, apparent molar isentropic compressibility, and infinite dilution apparent molar properties for transfer of ILs from water to aqueous polymer solution were scrutinised. From the gathered results, ion-water interactions, ion-ion interactions at finite concentration, and water-structure breaking character for aqueous solutions of [C4mim][HSO4] are more considerable than aqueous solutions of [C4mim]Br. However, [C4mim]Br-polymer interactions are more favourable than interactions between [C4mim][HSO4] and the studied polymers.</p