Dielectric study of dimethyl sulfoxide–water mixtures using the time-domain technique

Abstract

Complex dielectric spectra, ε*(ω)=ε′– iε″, in the frequency range 10 MHz–10 GHz have been determined using the time-domain reflectometry (TDR) technique at various temperatures for dimethyl sulfoxide–water mixtures. The dielectric spectra can be described by the Davidson–Cole relaxation model. The thermodynamic properties of the mixture have also been evaluated. The behaviour of the principal relaxation time of the mixture shows a maximum at a value corresponding to a mixture with 30% of water. An attempt has been made to explain the dielectric behaviour of binary mixtures by the hydrogen-bonding model as suggested by Luzar. The static relative permittivity of the mixtures can be explained if one assumes that the dipole moments of water and DMSO in the mixture are 14% and 10% larger than the corresponding values in the gas phase.