NANOSCALE SUPRAMOLECULAR ORDERING IN GEL-SURFACTANT COMPLEXES - SODIUM ALKYL SULFATES IN POLY(DIALLYLDIMETHYLAMMONIUM CHLORIDE)

Studies of slightly cross-linked polycationic gels interacting with an ionic surfactants have been performed by using random copolymers of po ly(diallyldimethylammonium chloride) (PDADMACl) and polyacrylamide (PA Am) with varying content of PDADMACl and degree of cross-linking Gel s amples which had been fully swollen in water were placed in aqueous so lutions of sodium alkyl sulfates (octyl (SOS), decyl-(SDCS), dodecyl ( SDS), tetradecyl (STS), and hexyl (SHS) sulfates). The degree of the s ample volume contraction depends on the PDADMACl content. The collapse d gel-surfactant complexes were studied using synchrotron small-angle X-ray scattering. All studied samples containing PDADMACl exhibited pr onounced supramolecular nanostructures. The gel-SDCS complex exhibited a cubic structure with a periodicity (7.75 nm) of approximately 4 tim es the surfactant molecular length, while the gel-SDS, gel-STS, and ge l-SHS complexes showed hexagonal supramolecular ordering with a period icity of approximately 2 times the surfactant molecular length. The d spacing of the longest periodicity in the complexes was dependent on t he PDADMACl content and the surfactant. The d spacing generally increa sed with decreasing PDADMACl (charge) content and increasing number of carbon atoms in the surfactant alkyl chain.