MICROSTRUCTURES FORMED IN A MIXED SYSTEM OF A CATIONIC POLYMER AND ANANIONIC SURFACTANT

Microstructures in a mixed solution of sodium dodecyl sulfate (SDS) an d the oppositely charged quaternary ammonium-substituted hydroxyethylc ellulose polymer JR-400 were imaged by two complementary methods: ligh t microscopy and cryo-transmission electron microscopy. Direct images were taken of the microstructures formed throughout the interaction zo nes at increasing SDS concentration. In solutions of low SDS concentra tion, bilayer fragments, small vesicles and disc-like aggregates form. As the SDS concentration is increased and approaches charge neutralit y, the solution becomes turbid. Particles imaged by light microscopy a nd 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 parti cles of different sizes, was imaged using light microscopy. Further ad dition of surfactant produced a turbid solution, where electron micros copy images indicated microphase separation with well developed flocs of spherical aggregates. At higher concentrations of SDS, resolubiliza tion took place and a variety of microstructures appeared: vesicles, d isc-like and thread-like structures. Upon increased surfactant excess, resolubilization was completed with the formation of spheroidal micel les. (C) 1997 Published by Elsevier Science B.V.