Surface Micellization Patterns of Quaternary Ammonium Surfactants on Mica

The microscopic equilibrium structures of adsorbed films of quaternary ammonium surfactants on mica have been investigated by noncontact atomic force microscopy imaging as a function of alkyl chain length and headgroup structure. Spherical and cylindrical surface micelles were observed; these were found to be related to bulk solution self-assembly and the surfactant packing parameter, v/a0lc. Shape transitions in the surface aggregates were observed on changing the counterion between chloride, bromide, and salicylate.