Anomalous Behavior of Fluorocarbon-Hydrocarbon Hybrid Surfactant in its Aqueous Solution. Surface Tension and Micropolarity.

Interfacial chemical behavior was studied for aqueous solutions of sodium 1-oxo-1- [4- (tridecafluorohexyl) phenyl] -2-hexanesulfonate, a hybrid surfactant containing a fluorocarbon chain and a hydrocarbon chain in the same molecule. Surface tension decreased substantially with an increase in surfactant concentration around the critical micelle concentration, followed by a secondary decrease. In the same concentration region the I1/I3 ratio in the fluorescence spectra of pyrene (added as a micropolarity-indicator) continued to be as high as the value in water despite the micelle formation and it began to decrease gradually from a concentration ten times greater than the cmc. Such a behavior suggests the micelle of the hybrid surfactant gradually changes its aggregation state even above cmc with the concentration increase.