Dielectric relaxation and thermodynamic properties of polyvinylpyrrolidone using time domain reflectometry

Temperature‐dependent values of dielectric permittivity ε′ and dielectric loss ε″ of polyvinylpyrrolidone (PVP, commercialized as PVP K‐60) solution of average molecular weight 160 000 g mol −1 were measured. The measurements were carried out in the frequency range 10 MHz to 20 GHz using time domain reflectometry at temperatures from 25 to 0 °C. The dielectric spectra can be described by the Davidson‐Cole model. Dielectric parameters such as the static dielectric constant ε 0 , the high frequency limiting dielectric constant ε ∞ , the relaxation time τ 0 and the distribution parameter β and thermodynamic parameters such as the free energy of activation Δ F τ , the enthalpy of activation Δ H τ and the entropy of activation Δ S τ were determined. The average free energy of activation was found to be in the range 12.55–14.65 KJ mol −1 and the enthalpy of activation was found to be 6.86 KJ mol −1 . Entropies of activation were found to be positive at all the measured temperature values and these large positive values of entropies reveal a less ordered structure of the PVP solution. The Kirkwood correlation factor g and the dipole moment µ were also determined for PVP solution. The results were compared with the results of the PVP‐water system studied previously. Copyright © 2011 Society of Chemical Industry