Time Domain Dielectric Spectroscopic Studies of Potassium Oleate and Cetyl Pyridinium Chloride in Acetate Buffer Solution

Abstract

Dielectric relaxation studies of acetate buffer solutions of anionic potassium oleate (PO) and cationic cetyl pyridinium chloride (CPC) surfactants at four different temperatures 283, 288, 293 and 298 K as a function of surfactant concentrations have been carried out in the 10 MHz to 30 GHz frequency range using time domain dielectric spectroscopy. Both the surfactants exhibit a significant rise of dielectric constant with increasing concentration. The corrected loss spectra of both the surfactants in aqueous buffer solution show up as peaks close to 1.4 GHz, and 14.5 GHz respectively. In agreement with the standard interpretation, we assigned the dominant mode at high frequency around 14.5 GHz to bulk water relaxation. The other peak around 1.4 GHz is attributed to hydration water reorientation of the surfactant micelles and has obtained detailed information on their temperature and concentration dependence. The relaxation times of bulk water and hydration water were calculated using Single Debye and Cole‐Cole method respectively. The activation enthalpy and activation entropy for the dipolar orientation for the surfactants at different concentrations have been calculated from the Arrhenius plot.