Micelle shape transformation in the isotropic phase of the ammonium perfluorooctanoate/heavy water binary mixture

The size and shape of the aggregates in the homogeneous isotropic micellar phase of the binary system ammonium perfluorooctanoate/heavy mater (APFO/D2 O) have been extensively investigated by small- and wide-angle X-ray scatte ring, optical polarizing microscopy, self-diffusion NMR, and electrical con ductivity techniques, as a function of temperature and surfactant concentra tion. The experimental results strongly suggest that there is a change in t he structure of the micellar aggregates where the micelles undergo a shape transition, changing from spherocylinder (rod-shaped), at low surfactant co ncentration (W-A < 26 mt % APFO), to disk-shaped micelles (oblate ellipsoid s), at high surfactant concentration (W-A > 28 wt % APFO).