Dielectric relaxation study of hexamethylphosphoramide-water mixtures using time domain reflectometry

The dielectric relaxation studies of hexamethylphosphoramide-water mixtures have been carried out at different temperatures using time domain reflectometry technique in the frequency range of 10 MHz to 10 GHz. A calibration method based on the least squares fit has been suggested to determine the complex permittivity at the high frequency region for the aqueous solutions. The excess dielectric, Kirkwood correlation factor and thermodynamic properties in the mixture have been determined. These properties suggest a Cage-type structure of hexamethylphosphoramide molecules around water molecules. The structure has a tendency to break down in the presence of water.