EFFECTS OF DISPERSION CONCENTRATION ON THE ELECTROACOUSTIC POTENTIALS OF O/W MINIEMULSIONS

Electroacoustic potentials are measured for toluene in water miniemulsions stabilized by cetyl alcohol (CA) and 10 mM sodium lauryl sulfate (SLS). The general trend with increasing CA concentration is a sharp drop in the potential up to 20 mM CA, after which the potential remains relatively constant as the CA concentration is further increased. The general trends in the electrokinetic sonic amplitude (ESA) and ζ-potential calculated ESA agree with the ζ-potential determined with microelectrophoresis for o/w miniemulsions prepared at several CA concentrations. However, the magnitude of the electroacoustic ζ-potential is two to three times lower than that of the electrophoretic ζ-potential. Dilution experiments show that the dynamic mobility varies linearly with the dispersion concentration, indicating that particle-particle interactions cancel in the electroacoustic field. The magnitude of the ζ-potential calculated from the dynamic mobility extrapolated to infinite dilution remains lower than that of the electrophoretic ζ-potential. Similar behavior is observed for a monodisperse polystyrene latex. © 1992.