Features of light scattering in aqueous solutions of dimethyl sulfoxide

Abstract

The water-dimethyl sulfoxide (DMSO) system was studied by means of static light scattering in the concentration range of 0 to 60 mol % DMSO at 20 and 50°C. In the concentration range of 10 mol % DMSO, an abnormal maximum of scattered light was detected, the intensity of which decreases with an increase of temperature. The formation of this maximum is related to hydrophobic effects in the system under study and the existence of an unattainable critical point of delayering. Temperature inversion of light scatter ing intensity was detected at ~14 mol % DMSO; at higher concentrations of DMSO, the intensity at 50°C is notably higher than at 20°C (due to the increase in the concentration's degree of fluctuation upon an increase in temperature); at 60 mol % DMSO, intensities of scattered light at 20 and 50°C almost coincide. The apparent molar volumes of DMSO in solutions were calculated from the published data on density in the tem perature range of 5 to 50°C. The minima of these values from 10 to 15 mol % DMSO (i.e., in the range of the abnormal maximum of scattered light) were obtained. The manifestation of hydrophobic effects in aqueous solutions of amphiphilic molecules is explained using the example of the DMSO-H 2 O system.

Revisiting the composition dependence of the properties of water-dimethyl sulfoxide liquid mixtures. Molecular dynamics computer simulations

“…This kind of composition behavior of apparent molar volumes of DMSO species in water-rich mixtures can be related to the experimental results for abnormal intensity of scattered light [51]. The minimum of [49]) at 298.15 K. Panels c and d: a comparison of the composition dependence of the apparent molar volumes of DMSO and of water from simulations, with the experimental data (squares reference [47] and triangles reference [50]) at 298.15 K. the apparent molar volume of DMSO indicates the hydrophobic effect in the systems in question due to enhanced concentration fluctuations within certain composition interval.…”

The local environment of the molecules in water–DMSO mixtures, as seen from computer simulations and Voronoi polyhedra analysis

“…The main feature of the DMSOwater mixture is that close to the DMSO mole percentage of 30-40% many physico-chemical properties, such as viscosity, 1,2 rotational correlation time of water, 3,4 translational diffusion, 5,6 static permittivity, 7 and thermophysical properties, [8][9][10][11] have an extrema. Many experimental [12][13][14][15][16][17][18][19][20][21][22] and theoretical studies [23][24][25][26][27][28][29][30][31] have been carried out on this system with the main objective of explaining this non-linear behaviour of the macroscopic properties of this mixture in terms of the intermolecular interactions (water-water, water-DMSO and DMSO-DMSO). In fact, there is a convergence in the literature that in the DMSO mole percentage range of 30-40% the water-DMSO interactions due to hydrogen bonds are at maximum.…”

Thermodynamics of Mixing Water with Dimethyl Sulfoxide, as Seen from Computer Simulations

“…Due to the full miscibility of these compounds, a broad range of desired properties can be achieved by tuning the composition of their mixture. These mixtures as well as neat DMSO have been extensively studied in the past decades both by experimental − and computer simulation methods. ,− These studies focused, among others, on two important general issues of aqueous solutions. The first issue is related to the effect of the solute on the structure of water in terms of enhancement or weakening of their tetrahedral arrangement, extent of the hydrogen bonding network, etc., whereas the second issue is related to the possible self-association of the solute (due to, e.g., hydrophobic interaction).…”