| 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 scattering 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 temperature 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-H2O system. |
