DIELECTRIC-RELAXATION STUDY OF HEXAMETHYLPHOSPHORAMIDE-WATER MIXTURESUSING TIME-DOMAIN REFLECTOMETRY

The dielectric relaxation studies of hexamethylphosphoramide-water mix tures have been carried out at different temperatures using time domai n 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 fo r the aqueous solutions. The excess dielectric, Kirkwood correlation f actor and thermodynamic properties in the mixture have been determined . These properties suggest a Cage-type structure of hexamethylphosphor amide molecules around water molecules. The structure has a tendency t o break down in the presence of water.