Surface Electrical Properties of Polystyrene Latex

The surface electrical properties of a polystyrene latex have been studied with several experimental methods. Previous studies by other authors have shown discrepancies between the surface potential and the surface charge density determined by different methods. This work is an attempt to produce more experimental data for the discussion concerning these discrepancies. Both electrophoretic mobility and electrical conductivity methods have been used. Also, gel permeation chromatography has been used to estimate the number of endgroups on the latex particle that carry charged surface groups. Synthesis and cleaning methods of polystyrene latex are also discussed. Calculations on a Poisson-Boltzmann level of approximation have been performed in an attempt to connect the quantities determined with dynamic (electrophoresis and static conductivity) methods and static (titration) methods. The discrepancies can be explained by introducing a pH- and electrolyte-dependent surface structure such as the hairy layer model. A Stern layer conductance model can also to some extent explain these discrepancies, but this model contains several parameters not directly attainable by experiments. This means that a unique set of parameters cannot be determined without further studies on several latex systems. Copyright 1999 Academic Press.