Salt effect on solutions of nonionic surfactants and its influence on the stability of polymerized microemulsions

Abstract

The effect of various salts on the cloud points of nonionic surfactant solutions has been studied by turbidimetry. The elevation or depression of cloud points can be discussed in terms of salting in or salting out, respectively. Assignment of cloud point shift values to the individual ions forming the electrolyte shows that the salting effects are mainly due to the prominent influence of the anions as compared to that of the cations. The salt effects are shown to affect the stability of inverse polyacrylamide microlatexes prepared by polymerization in nonionic microemulsions. Addition of electrolytes with high salting out efficiency, such as sodium acetate, induces the phase transition Winsor I → Winsor III. This allows the polymerization of monomers in bicontinuous microemulsions characterized by low interfacial tensions (⋍10 −3 dyn cm −1), which subsequently leads to clear and stable inverse microlatexes.