Open Access

Matthias Frangenberg, Annette M. Schmidt, Jan Wilkens

• Surface conductivity can have a significant impact on the determination of the zeta potential, but it is normally not accounted for when applying the Helmholtz-Smoluchowski or Henry models. In this study, we investigate concentrated polymer dispersions using electroacoustics and both standard models. We also pay particular attention to the influence of surface conductivity, which is characterized by conductivity measurements of the dispersion and dispersion medium. The Dukhin number as a measure of surface conductivity is calculated according to Maxwell–Wagner-O’Konski theory. Zeta potentials were determined by means of colloid vibration current (CVI) and electrophoretic light scattering (ELS) methods. It has been found that neglecting surface conductivity in standard electrokinetic models can lead to large measurement errors of up to 100% with increasing particle volume fraction. In this study, the surface conductivity is now correctly taken into account by using the conductivities of the dispersion and the dispersion medium. Alternatively, this influence can also be considered using the Dukhin number. The zeta potentials resulting from the CVI measurement are then in excellent agreement with ELS reference measurements over a wide volume fraction range.