SMALL-ANGLE SCATTERING STUDY OF PERFLUOROPOLYETHERS WATER-SYSTEMS

Small angle neutron and X-ray scattering (SANS and SAXS) were carried out on aqueous solutions of perfluorinated polyether carboxylates (PFPE). The scattering intensity of concentrated solutions displayed a series of sharp maxima indicative of a solution structure caused by the electronic interactions among particles. The interparticle distance was scaled as the inverse of the surfactant volume fraction. Such an 'ideal'' one-dimensional swelling was evidence of a very stable smectic structure. The determination of the thickness from the peak position allowed identification of the presence of a bilayer lamellar structure. The scattering behavior at low concentration was interpreted as originated from locally flat particles which could be large vesicles. Between the ''ideal'' one-dimensional swelling and the isotropic regions, a biphasic domain (L(alpha) + L3) in which a maximum swelling occurred was found. The effect of counterions and of chain length was also studied.