Ternary complexes with poly(β-cyclodextrin), cationic surfactant, and polyanion in dilute aqueous solution:: A viscometric and small-angle neutron scattering study

Phase diagrams have been investigated for four-component systems with a poly(P-cyclodextrin), a cationic surfactant, and a polyanion in water. For a soluble mixture, small-angle neutron scattering and viscometry have been used to demonstrate the formation of poly(beta-cyclodextrin)/dodecyltrimethylammonium chloride (DTAC)/sodium dextran sulfate complexes. For fixed concentrations of the two polymers, it was found that the addition of a specific amount of surfactant caused a radical change in the structure of the complexes. Below this critical concentration, the formed aggregates are of low density and diffuse. Above this concentration of surfactant, complexes become more and more compact up to precipitation. This structural transition of the ternary complexes has been related to the architecture of the poly(beta-CD)/DTAC complex which shows a marked polyelectrolyte behavior for DTAC quantities higher than the critical concentration. Viscosity and SANS results have been attributed to a difference of distribution of DTAC along the poly(P-cyclodextrin) chains: an inhomogeneous distribution up to the critical DTAC concentration, surfactant monomers being distributed on a spherical outer shell, and a more homogeneous distribution beyond this concentration.