A dielectric study of the structure of propylene glycol

The dielectric spectra of propylene glycol over the frequency and temperature ranges 10 mHz–75 GHz and 175–423 K, respectively, were analyzed using the Dissado-Hill cluster model. A correlation between relaxation processes of breaking and formation of intermolecular H-bonds in clusters was obtained. A correlation of fluctuation processes of synchronous exchange of molecules between neighboring clusters corresponded to the redistribution of H-bonds between them. The Dissado-Hill theory was used to determine the integral relaxation times, n _DH and m _DH parameters and calculate the mean dipole moments of propylene glycol clusters and the energy characteristics of processes of their rearrangement. The mean dipole moments of clusters (23617–18.65 D) were compared with those of molecules in the liquid phase (3.67–3.03 D). The apparent activation enthalpy of processes of cluster rearrangements decreased from 141.8 to 25.2 kJ/mol, the activation energy decreased from 46.03 to 18.47 kJ/mol, and the energy of orientation dipole-dipole interactions, from 3.78 to 3.45 kJ/mol as the temperature increased.