Temperature dependent association and relaxation in monoalkyl ethers of ethylene glycol and of diethylene glycol in dilute solutions of benzene from static and complex microwave dielectric measurements

The dielectric properties of two homologous series of ethylene oxide condensation products i.e. monoalkyl ethers of ethylene glycol and monoalkyl ethers of diethylene glycol have been investigated in dilute solutions of benzene at 20 degrees C, 35 degrees C and 45 degrees C to clarify the structural dynamics of these molecules. The low frequency molecular dynamics of these molecules have been studied by evaluating the Kirkwood correlation factor, molar polarization and dipole moment using the 1 MHz static dielectric constant and the dielectric constant of induced polarization. The observed values of the Kirkwood correlation factor significantly deviated from unity confirm the intermolecular association in these molecules in dilute solutions. The high frequency molecular dynamics were examined using 9.83 GHz microwave dielectric relaxation times corresponding to overall rotation and group rotations. These relaxation times have been discussed in terms of the effect of chain length, viscosity, size of alkoxy groups and molecular association with temperature variation. A switch-over type of mechanism is also discussed in these associating molecules due to breaking and reforming of hydrogen bonds, considering the temperature dependent dielectric, parameters. The dynamics of these molecules have been compared to the rather similar behaviour of small chain and long chain associating molecules. (C) 1999 Elsevier Science B.V. All rights reserved.