PROBLEMS ASSOCIATED WITH THE SURFACE CHARACTERIZATION OF POLYSTYRENE LATTICES

Experimental data are presented which show that polystyrene latices prepared by the surfactant free emulsion polymerization process often contain sufficient residual monomer and possibly low-molecular-weight material and reaction by-products, such as benzaldehyde, which are not efficiently removed by dialysis, to affect their bulk and surface characteristics. These materials have been identified by gel permeation chromatography (GPC) and infrared (IR) spectroscopy studies and their effective removal by steam stripping has been investigated. Steam stripping has proved to be efficient in this process but it led to rapid hydrolysis of the surface sulfate groups and a consequent change in the surface characteristics. The problem of hydrolysis of sulfate groups under various environments has been studied. The problems associated with the identification of weak acid end groups are discussed and several alternative explanations for their occurrence are advanced.