Dielectric Relaxation and Dipolar correlation in Pyridine – Propylene Glycol Mixture; A Time Domain Reflectometry Study using the Cole –Davidson Model

The dielectric relaxation behaviour of pyridine (Py), dissolved in propylene glycol(PG) as a solvent, was investigated by using time-domain reflectometry (TDR) in the frequency range of 10–50 GHz and temperatures 283.15–298.15 K. The complex permittivity spectra (CPS) were analysed to understand molecular interactions and dipolar relaxation dynamics. The measured spectra were fitted using Cole–Davidson model to obtain static dielectric constant (ε0) and relaxation time (τ). The excess permittivity, Kirkwood correlation factor, thermodynamic properties and Bruggeman factor indicate varying degrees of dipole correlation, reflecting the structural and dynamic interplay between solute and solvent. The obtained data have been analysed in terms of the parallel and antiparallel orientation of the dipoles, chain length and hydrogen bond interaction in the mixture composition.