Dielectric relaxation studies of acetonitrile/propylene glycol and their binary mixtures

Dielectric relaxation spectra in the frequency range 0.02 < v/GHz < 20 have been collected for propylene glycol (PG), acetonitrile (AN) and their binary mixtures between 303 K-323 K. The average relaxation times have been calculated by the Cole-Davidson and Cole-Cole relaxation models. The experimental determined values of static dielectric permittivity (epsilon(0)), relaxation time (tau), excess permittivity (epsilon(E)) and excess inverse relaxation time (1/tau)(E) show smooth temperature dependence. The larger relaxation time values of propylene glycol when compared to acetonitrile are due to the co-operative process of multimers with O-H-O linkage and also the steric hindrance behavior phenomena. The activation entropy (Delta S*), activation enthalpy (Delta H*), Kirkwood correlation factor (g(f)), Helmholtz energy (Delta F-E) parameters have also been determined for propylene glycol and acetonitrile and the results have been correlated.