Small-angle X-ray and neutron scattering (SAXS and SANS, respectively) have been measured in H2O solutions of cesium perfluorooctanoate (CsPFO) in the concentration range 0.065-0.5 M (much lower than the boundary between isotropic and discotic nematic phases). For 0.1 and 0.3 M solutions, SANS has been measured for various D2O/H2O mixed solvents. The data have been analyzed with a double-layered ellipsoid form factor combined with the rescaled mean spherical approximation for the intermicellar structure factor. The scattering curves can be fitted well with both prolate and oblate ellipsoid models. However, the semiminor axis of micellar core, Rc, obtained for the prolate ellipsoid (15.3 Å) is much longer than the extended length of the fluorocarbon chain (12.6 Å) which is close to the Rc obtained for the oblate ellipsoid (13.0 Å). As the surfactant concentration increases, both the aggregation number and the degree of counterion binding increase. These results suggest micellar growth along two dimensions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry