Tuning microstructure of cationic micelles on multiple length scales: The role of electrostatics and specific ion binding

Small-angle neutron scattering has been used to obtain detailed information on local structure, including micellar cross-sectional radii, areas per he adgroup, and number of surfactant molecules per unit length for mixed micel les of cetyltrimethylammonium 2,6-dichlorobenzoate and cetyltrimethylammoni um chloride in water as a function of surfactant and salt concentrations an d the relative amounts of the two counterions (the counterion inventory) at the micellar surface. The differing effects of penetrating (2,6 -dichlorob enzoate) and nonpenetrating (chloride) counterions on micellar surface char ge density and on the relative energies of surfactant monomers in cylindric al vs end-cap micellar environments are elucidated.