Permittivity spectrum of polystyrene-latex suspensions

Abstract

The complex permittivity of ionogenic polystyrene latex particles in water has been investigated over a range of frequency, electrolyte concentration and temperature. The dielectric spectra showed two distinct dispersions similar to the β- and δ-dispersions found for protein solutions. The values of parameters for a double relaxation were calculated by fitting the function to the complex permittivity.

The β-dispersion was assumed to be due to the relaxation of the counterion atmosphere around the particles polarized by the applied electric field. From the parameters for the β-dispersion, values of the surface charge, surface conductivity and capacity, and counterion mobility have been calculated.

Three theories are put forward and tested to explain the δ-dispersion; (a) relaxation of bound water at the particle surface; (b) relaxation of an inner counterion atmosphere around the particles polarized by the applied electric field (i.e., the δ- and β-dispersions are due to the relaxation of Stern, and Gouy layers respectively); (c) a frequency-independent surface conductivity. Theory (a) is discounted, although the existence of bound water is not denied. Theories (b) and (c) both explain the δ-dispersion equally well, although there are some anomalies in each case.