Phase Behavior of the Supercooled Aqueous Solutions of Dimethyl Sulfoxide, Ethylene Glycol, and Methanol As Seen by Dielectric Spectroscopy

Abstract

The dielectric behavior of the supercooled aqueous solutions of dimethyl sulfoxide (DMSO), ethylene glycol (EG), and methanol (MeOH) has been examined in the frequency range 106−10-3 Hz and in the x m range of 0.19−0.40, 0.25−0.85, and 0.50−0.85, respectively, where x m is the mole fraction of the second component. Differential scanning calorimetric measurements have also been carried out on the samples. At temperatures above the glass transition temperature (T g), it was found that the Hevriliak−Negami relaxation function is appropriate to describe the data. The “apparent” distribution in relaxation times increases with increasing water content and also on lowering the temperature. But at temperatures just above T g, an Arrhenius branch of considerable polarization and with an activation energy of ∼21.5 kJ/mol separates out to continue to the sub-T g region, which more or less disappears around x m = 0.33 in DMSO solutions and around x m = 0.50 in EG solutions. It is suggested that the complexes of 2:1 (in DMSO solutions) and 1:1 (in EG solutions) are present in the liquid that are thermolabile and exist in an undissociated state only near T g, and the sub-T g process is due to the relaxation of water molecules. No evidence of complex formation is found in MeOH solutions.

Molecular dynamics simulations of sodium chloride solutions in water–dimethyl sulphoxide mixtures: Potentials of mean force and solvation structures

“…There is no general agreement about the mechanism by which the two solvents interact to account for these macroscopic deviations. 23 However, it has been well established that the water-DMSO hydrogen bond is much stronger than the water-water hydrogen bond, 8 which has been accepted to be one of the major reasons for the deviations in macroscopic properties. The associative properties of DMSO responsible for the nonidealities in water-DMSO mixtures are also found in its associations with polarizable nonionic and ionic substances.…”

Dielectric Spectroscopy in Ibuprofen-Dioxane Mixture

“…The parameter α HN is a measure of the distribution of relaxation times in the sample, and the parameter (1-β HN ) is a measure of cooperation among the molecules. The exact identity of peak loss frequency (f m ) [27] is determined with the help of the estimated values of α HN , β HN and f 0 as,…”

Acetaminophen, Methocarbamol, Guaifenesin and Mephenesin in Propylene Glycol: Solubility and Phase Behaviour for Use in Medical Industry

“…The parameter αHN is a measure of the distribution of relaxation times in the sample, and the parameter (1-βHN) is a measure of cooperativity among the molecules. The peak loss frequency fm is determined with the help of the estimated values of αHN, βHN and f0 [28] as, ( …”