Micellar Growth in Salt-Free Aqueous Solutions of a Gemini Cationic Surfactant: Evidence for a Multimodal Population of Aggregates

We study salt-free aqueous solutions of a cationic gemini surfactant in the concentration range between the critical micellar concentration and the onset of the semidilute regime by combining SAXS, static and dynamic light-scattering techniques. The results give strong evidence for the coexistence of small, intermediate, and very large micellar sizes in the whole range of concentration. The qualitative evolution of the different micellar populations could be followed as a function of concentration and is found in good qualitative agreement with recent cryo-TEM observations on the same system by Bernheim-Grosswasser et al.