NONCRITICAL BEHAVIOR NEAR THE CLOUD POINT IN PERFLUORINATED IONIC MICELLAR SOLUTIONS

The solution properties of a noncritical cloud point system, namely, sodium perfluorooctanoate/H2O/tetrapropylammonium bromide, were investigated by dynamic and static light scattering. Critical-type behavior is observed when the temperature approaches the minimum cloud point (T(d)) from the one-phase region: However, for other sodium perfluorooctanoate solutions, but of lower concentration than that corresponding to the minimum cloud-point temperature, the apparent hydrodynamic radius may decrease as the temperature approaches the cloud point. It is thus shown that a cloud-point system may not always exhibit critical-type behavior as many authors believe in the literature.