Hydrogenated/fluorinated catanionic surfactants as potential templates for nanostructure design

The structure and physicochemical properties of the nanoparticles spontaneously formed within aqueous mixtures of the hydrogenated/fluorinated catanionic surfactant cetyltrimetylammonium perfluorooctanoate in the absence of counterions as a function of its concentration are investigated by a combined experimental/computational study at room temperature. Apparent molar volumes, isentropic apparent molar compressibilities, and dynamic light scattering measurements together with transmission and cryo-scanning electron as well as confocal laser microscopy images, and computational molecular dynamics simulations indicate that a variety of structures of different sizes coexist in solution with vesicles of ～160 nm diameter. Interestingly, the obtained nanostructures were observed to self-assemble from a random distribution of monomers in a time scale easily accessible by atomistic classical molecular dynamics simulations, allowing to provide a comprehensive structural and dynamic characterization of the surfactant molecules at atomic level within the different aggregates. Overall, it is demonstrated that the use of mixed fluorinated hydrogenated surfactant systems represents an easy strategy for the design of specific nanoscale structures. The detailed structural analysis provided in the present work is expected to be useful as a reference to guide the design of new nanoparticles based on different hydrogenated/fluorinated catanionic surfactants.