Formation of mixed micelles of PB40PEO62 and the anionic surfactant SDS in aqueous solutions

Abstract

Co-micellisation of the di-block copolymer polybutadiene-poly(ethylene oxide) (B₄₀-b-EO₆₂) with the anionic surfactant sodium dodecylsulfate (SDS) was investigated in aqueous solution using different scattering methods and cryo-transmission electron microscopy. In dilute aqueous solutions this polymer forms large wormlike micelles coexisting with spherical ones. Upon addition of the surfactant, the large, mainly wormlike block copolymer micelles exhibit a structural change. Mixed micelles of polymer and surfactant are formed and the size of the mixed aggregates changes in dependence on the amount of SDS. At a certain limiting concentration of SDS, only spherical mixed micelles with a radius of ca. 13 nm and a low polydispersity are observed in the solution. Further addition of surfactant does not induce any further structural change.