Scaling behavior of the high-frequency dielectric properties of poly-L-lysine aqueous solutions

We report the scaling behavior of the dielectric parameters, the dielectric strength Delta epsilon and the relaxation time tau, of the high-frequency dielectric dispersions observed in aqueous solutions of poly-L-lysine of di fferent molecular weights, from 4000 to 167 000. The dielectric properties have been measured in the frequency range from 1 MHz to 1.8 GHz, and the di spersions have been attributed to internal motions of side chain polar grou ps, resulting in an intermediate relaxation process between that due to the counterion atmosphere polarization and that due to the orientational polar ization of the water molecules. The scaling relationships are compared with the predictions of the dynamic scaling theory recently surveyed by Dobryni n, Colby, and Rubinstein (Macromolecules 1995, 28, 1859) developed to descr ibe both the dilute and semidilute regimes of aqueous polyelectrolyte solut ions. Our data, based on the analysis of a new set of dielectric measuremen ts of poly-L-lysine aqueous solutions over an extended range of polymer con centrations and temperatures for each of the molecular weights investigated , are qualitatively consistent with this scaling picture. Deviations from t he predicted indices in the power law behavior of the relaxation time in th e high molecular weight polymer solutions are briefly discussed.