A comparison of electroacoustic and microelectrophoretic zeta potential data for titania in the absence and presence of a poly (vinyl alcohol) adlayer

Abstract

The recently developed technique of electroacoustics can measure the zeta potential in relatively concentrated (0.1–50 vol%) particle dispersions that cannot be analyzed by conventional microelectrophoresis. In this research, the MATEC Applied Sciences ESA 8000 electroacoustic apparatus is used to determine the zeta potential of aqueous colloidal anatase titania in the absence and presence of 88 mol% poly (vinyl alcohol), PVA, which adsorbs strongly to the titania surface. For both the bare titania and the titania/PVA adlayer systems the electroacoustically determined zeta potential data are in agreement with data collected on the Bank Bros. Mk. II microelectrophoresis apparatus, provided that the electroacoustic data are corrected for the effect of particle inertia.For all pH values the presence of a PVA adlayer acts to decrease the magnitude of the zeta potential. Since the PVA does not significantly change the surface charge density of the titania, this decrease is interpreted as an outward shift in the shear plane location. A diffuse double layer potential profile is then used to calculate an effective adlayer thickness from the zeta potential data. The calculated adlayer thickness is found to increase with nominal polymer molecular weight.