SOME EXPERIMENTAL AND THEORETICAL DATA ON THE DIELECTRIC-RELAXATION IN DILUTE POLYSTYRENE SUSPENSIONS

The study of the conductivity and dielectric response of colloidal suspensions when subjected to an alternating electric field can give a great deal of information on the characteristics of the solid-liquid interface, as well as on the dynamic processes taking place in such systems. In fact, measurements of the dielectric relaxation spectra on colloids are more sensitive to the nature of the surfaces than any other electrokinetic technique. This work deals with this problem in dilute polystyrene suspensions. Their complex conductivity and dielectric constant are experimentally measured as a function of both the frequency of the applied field and the latex volume fraction, in KCl solutions. From these data, certain quantities have been obtained that can be compared to the predictions of advanced theoretical models. The agreement between theoretical and experimental data is qualitatively excellent, although the latter are significantly larger that the former. Reasons for such discrepancies are discussed in the light of recent experimental results and double layer models.