The micellar properties such as critical micelle concentration (cmc), counterion binding, and the micellar growth of cationic fluorocarbon surfactant, diethanolheptadecafluoro-2-undecanol methylammonium chloride (DEFUMACl), were studied by dynamic light scattering (DLS), transient electric birefringence (TEB) and viscosity measurements. The micellar growth of DEFUMACl was induced by increasing DEFUMACl concentration and adding inorganic salt (NaCl). The cmc of DEFUMACl is 3.8 mmol•L^－1. The results clearly showed that the spherical micelles were elongated to rod-like micelles by addition of salt in a dilute DEFUMACl solution or increasing DEFUMACl concentra-tion. The second critical micelle concentration (cmc_II) was determined to be 0.2 mol•L^－1 by conductivity measurements. The aggregation numbers of spherical and rod-like micelles were calculated to be 45 and 335, respectively.

Key words: cationic fluorocarbon surfactant, micelle, salt effect, dynamic light scattering, transient electric birefringence