Abstract
The presence of anion and cation adsorption to the surfaces of emulsifier free emulsion polymerized latex particles is studied. Electrophoretic mobilities and suspension conductivity increments for particles suspended in HCl, KCl, and HClO 4 were determined over a wide range of electrolyte concentration using conventional techniques. In addition a nonelectrokinetic experimental technique was developed to measure the total concentration of ions adsorbed to the latex surface. Here a determination is made of the total concentration of ions required to bring an exhaustively cleaned latex into equilibrium with a dialysate of fixed concentration. This quantity of ions is called the added electrolyte and becomes a linear function of the volume fraction in the limit of low volume fraction. The slope of this curve, the added electrolyte increment, provides a quantitative measure of ion adsorption. Poor comparisons were found between measured added electrolyte increments and those predicted by the Gouy-Chapman model for the diffuse double layer on the basis of surface potentials determined from electrokinetic measurements assuming no ion adsorption. However, when ion adsorption is allowed and site binding parameters are determined by fitting electrokinetic data with the dynamic Stern layer model, good agreement is found between measured and predicted added electrolyte increments.
Published Version
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