Densities, speeds of sound, refractive indices, excess and partial molar properties of polyethylene glycol 200 + benzyl methacrylate binary mixtures at temperatures from 293.15 to 318.15 K

Unusual Hydration Properties of Choline Fluoride-Based Deep Eutectic Solvents

The hydration properties of the fluoride-based deep eutectic solvent ethalineF [a solution of choline fluoride in ethylene glycol (EG) at a 1:2 molar ratio] are studied and compared to the most common deep eutectic solvent ethaline (the solution of choline chloride in EG at 1:2 molar ratio). The densities of the deep eutectic solvent (DES) based on choline fluoride in EG (ethalineF) and its mixtures with water as cosolvent are measured over the temperature range of 298-323 K. The excess properties, including excess molar volumes, excess partial molar volumes, and viscosity deviations from ideal behavior, are calculated for ethalineF/water and ethaline/water mixtures and compared. The experimental excess molar volumes and viscosity deviations of the studied pseudobinary mixtures are fitted using the Redlich-Kister (R-K) equation. The results of the R-K model successfully reproduced the experimentally calculated values with minimal standard deviations. All excess molar volumes and viscosity deviations had negative values, indicating stronger solvation interactions between the mixture components than between each pure DES or water. The excess partial molar volumes show that water molecules are preferentially solvated by the DES environment. We show that the disruption of the DES interactions (primarily OH...halide interactions) by high mole fractions of water is related to the peak ionic conductivity. The stark differences in hydration behavior between fluoride- and chloride-based ethaline are analyzed and discussed.

The Group Contribution to the Function Derived from Density and Speed-of-Sound Measurements for Glymes in N,N-Dimethylformamide + Water Mixtures

The density and speed of sound of pentaglyme and hexaglyme in the N,N-dimethylformamide + water mixture at four temperatures are presented. The limiting apparent molar volumes (VΦ,m0=Vm0), the isobaric molar thermal expansion (Ep,m0), the isentropic compressibility (κS), and the limiting partial molar isentropic compression (KS,Φ,m0 = KS,m0) were calculated. Changes in the values obtained from the physicochemical parameters, as functions of composition and temperature, were analyzed in terms of the molecular interactions and structural differentiation of the investigated systems. The hydrophobic hydration process of the studied glymes was visible in the area of high water content in the mixture. The hydration number of glymes in water at four temperatures was calculated and analyzed. The contribution of the -CH₂- and -O- group to the functions describing the volume and acoustic properties of the investigated system was calculated. The calculated values of the functions analyzed using the group contribution are in agreement with the values obtained from the experimental data. Thus, such contributions are valuable for wide ranges of data, which can be used to analyze the hydrophobic hydration and preferential solvation processes, as well as to calculate the values of these functions for other similar compounds.

Hybrid Polyethylene Glycol/Sodium Metaphosphate Composites Prepared via Coacervation

We report on the fabrication and characterization of homogeneous, monophasic sodium metaphosphate and polyethylene glycol hybrid composites achieved via coacervation in aqueous solution. After separation and drying, an amorphous plastic solid is formed, composed mostly of hydrated sodium phosphate moieties amalgamated with polyethylene glycol chains. These composites are largely X-ray amorphous and can contain up to 8 weight percent of polymer. Impedance spectroscopic measurements reveal DC conductivity values of 12 μS/m at room temperature, an enhancement of three orders of magnitude when compared to glassy sodium metaphosphate, and the presence of the polyethylene glycol is reflected in the equivalent circuit and ionic hopping analyses.