Microstructures formed in a mixed system of a cationic polymer and an anionic surfactant

Abstract

Microstructures in a mixed solution of sodium dodecyl sulfate (SDS) and the oppositely charged quaternary ammonium-substituted hydroxyethylcellulose polymer JR-400 were imaged by two complementary methods: light microscopy and cryo-transmission electron microscopy. Direct images were taken of the microstructures formed throughout the interaction zones at increasing SDS concentration. In solutions of low SDS concentration, bilayer fragments, small vesicles and disc-like aggregates form. As the SDS concentration is increased and approaches charge neutrality, the solution becomes turbid. Particles imaged by light microscopy and electron microscopy indicate microphase separation with clear flocs of mainly globular structure. No microstructures were observed in the supernatant in the precipitation zone. The precipitate, made of particles of different sizes, was imaged using light microscopy. Further addition of surfactant produced a turbid solution, where electron microscopy images indicated microphase separation with well developed flocs of spherical aggregates. At higher concentrations of SDS, resolubilization took place and a variety of microstructures appeared: vesicles, disc-like and thread-like structures. Upon increased surfactant excess, resolubilization was completed with the formation of spheroidal micelles.