Polymer effects on the equimolar mixed cationic–anionic surfactants

Interactions between poly(ethylene oxide) (PEO), and equimolar mixed sodium decylsulfonate and decyltriethylammonium bromide were studied using surface tension, fluorescence, dynamic light scattering and freeze-fracture transmission electron microscopy techniques. Below the cmc of the equimolar mixed cationic–anionic surfactants, no obvious interaction was observed under the experimental conditions. However, PEO had dramatic effects on the morphology of the aggregates of the equimolar mixed cationic–anionic surfactants. Spontaneous, stable and narrow distributed vesicles could be prepared by mixing PEO and equimolar mixed cationic–anionic surfactants. Furthermore, the size of the vesicles could be controlled by turning the total surfactant concentration, PEO concentration and PEO molecular weight. We found the effect of PEO on the vesicles could be explained by the Asakura–Oosawa model.