Determination of the saturation adsorption of surfactant in polymer latices

The volumetric determination of the surfactant adsorption density at maximum packing (saturation) is studied in binary latex blends. A phenomenological description for latex mixtures that are not free of surfactant prior to titration predicts a quadratic dependence for the saturation adsorption density as a function of the fractional surface area of the latex compounds. The expected behavior was verified experimentally from conductometric titrations of sodium dodecyl sulfate in blends of homopolymer latices cleaned with the serum replacement technique. Accordingly, it is shown that surfactant titration of binary latex blends provides indications about the level of cleaning of the mixed compounds. Furthermore, when latex mixtures are prepared by using a surfactant-free reference latex, this approach may be used for the estimation of the saturation adsorption area of the bare polymer surface for an incompletely cleaned latex. (C) 2004 Wiley Periodicals, Inc.