Interaction of Polystyrene-<i>block</i>-poly(ethylene oxide) Micelles with Cationic Surfactant in Aqueous Solutions. Metal Colloid Formation in Hybrid Systems

Abstract

The interaction of the amphiphilic block copolymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO), with cationic surfactant, cetylpyridinium chloride (CPC), in aqueous media was studied by static light scattering and analytical ultracentrifugation. Three well-defined populations of hybrid structures corresponding to micelles, micellar clusters, and supermicellar aggregates were found to exist in the PS-b-PEO/CPC aqueous solutions at a block copolymer concentration of 10 g/L. The relative ratio of each type of structure and their parameters strongly depend on the CPC concentration, mobility of the polystyrene micellar core, and chemical composition of the dispersing media. Ion exchange of the surfactant counterions in the hybrid PS-b-PEO/CPC system by PtCl62- and PdCl42- ions resulted in saturation of the micellar structures with noble metal ions. The subsequent reduction of the metal-containing PS-b-PEO/CPC/MXn species with NaBH4 and molecular hydrogen resulted in the formation of metal nanoparticles mainly located in the block copolymer micelles.