REGULAR MICROSTRUCTURES IN GEL-SURFACTANT COMPLEXES - INFLUENCE OF WATER-CONTENT AND COMPARISON WITH THE SURFACTANT STRUCTURE IN WATER

Interaction of slightly crosslinked hydrogels of poly(diallyldimethyla mmonium chloride) (PDADMACI) and of copolymer DADMACl/acrylamide (AAm) with sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfate (SD BS) results in significant shrinking of the gels due to the formation of polymer-surfactant complexes. Jump-wise transitions in the collapse d state were observed for the networks with the content of cationic gr oups 100 and 75 mol %. The structure of complexes was studied by means of X-ray scattering method. The scattering curves for collapsed gels, where most chloride anions were replaced by anions of SDS, show a set of well-pronounced narrow diffraction maxima. Fully charged ''wet'' c omplexes studied at the equilibrium swelling conditions exhibit high d egree of ordering, which diminishes upon drying with the simultaneous transition from hexagonal to lamellar type of ordering. In contrast to this, for DADMACl/AAm copolymer gels (75 mol % of DADMACl monomers in the initial polymerization mixture) the ordering is less pronounced i n the ''wet'' state and becomes more perfect upon drying. The SDS aque ous solutions of the same concentration in the absence of gel do not s how such high degree of ordering, while the system of SDS/neutral AAm gel exhibits lamellar ordering typical for low-temperature phases of S DS solutions. (C) 1996 John Wiley & Sons, Inc.