Complexation of Ionomers and Surfactant Molecules of the Same Charge in a Nonpolar Solvent

Abstract

Complexation between sulfonated polystyrene ionomers and bis(2-ethylhexyl) sulfosuccinate sodium salt (aerosol OT, AOT) surfactant molecules in m-xylene was studied by ultracentrifugation, vapor pressure osmometry, viscometry, and dynamic light scattering. When the dilute ionomer solution is mixed with the AOT solution, complexation takes place for both the slightly aggregated state of AOT and reversed micelles of AOT containing water. In the presence of excess AOT molecules, some of the AOT are free from the ionomers, and there are well-defined limiting compositions for complexes of the ionomer and AOT and for those of the ionomer and AOT micelles. The limiting composition depends on the species of the salt or acid group of the ionomer and on the state of AOT before mixing. The composition was estimated to be 0.21--0.66 reversed AOT micelles per salt/acid group for the ionomer--AOT micelles complexes and 14--23 AOT molecules per salt/acid group for the ionomer--AOT complexes. AOT molecules were found to disrupt efficiently the cluster-forming contacts among salt/acid groups, each of them encapsulating a single salt/acid group. The AOT micelles, however, do not completely disrupt the intrachain aggregation.