The microstructure and rheology of mixed cationic/anionic wormlike micelles

The rheology, flow birefringence, and small-angle neutron scattering of mixed cationic/anionic wormlike micellar solutions composed of cetyl trimethylammonium. tosylate (CTAT) and sodium dodecyl benzyl sulfonate (SDBS) are studied over a broad range of solution compositions. This combination of experimental techniques enables independent determination of the microstructural length scales (persistence, entanglement, interaction, and contour) that govern the rheological properties. Comparison and contrast of the effect of a hydrotropic salt (NaTosylate) with that of a screening electrolyte (NaCl) demonstrates the influence of micellar charge on the persistence length and, hence, the microstructure and rheology. Surfactant concentration and composition and electrolyte concentration and composition systematically affect the self-assembled microstructure such that a transition in rheological behavior from nonionic wormlike micelles to polyelectrolytes can be spanned.