Dielectric relaxation studies of nitriles solubilized by Sodium dodecyl sulphate in aqueous solutions

Dielectric relaxation studies of aqueous sodium Dodecyl Sulphate with acetonitrile & benzonitrile, have been carried out for different concentrations at 303 K. Dielectric Relaxation Spectroscopy (DRS) is a versatile tool to monitor the dynamic process of micellar systems. The time domain dielectric data were obtained in the reflection mode in the frequency range of 10 MHz to 20 GHz using a HP54750A sampling oscilloscope and HP54754A TDR plug-in-module. The sample is held at 303 k in a Standard Military Application cell with an effective pin length of 1.35 mm. We have determined the relaxation time (τ) using the Debye method. The relative viscosity ηr on the micellar solutions was also determined. We find that ηr increases with concentrations of sodium dodecyl sulphate and there is a non-linear increase in ηr beyond 80 mM of sodium dodecyl sulphate. The observed relaxation time is explained by considering a superposition of two relaxation times. One is due to the rotation of the hydrated water around the micelle ions and the other due to the hydrated water squeezed in the hydrophobic interior of the micelle. Our results are explained on this basis.