Determination of micellar aggregation numbers of Gemini surfactants

The critical micelle concentration (CMC) and micellar aggregation numbers of series of cationic Gemini surfactants are determined by steady-state fluorescence probe method in which pyrene was used as a fluorescence probe and cetylpyridinium chloride as a quencher. The experimental results indicate that the CMC values are basically in agreement with the values determined by conductivity method, the aggregation numbers of this series cationic Gemini surfactants are essentially constant when the concentrations of the quencher are in 0.20 to 0.50 mmol/L. The aggregation numbers of the Gemini surfactant (16-X-16) increases linearly with the increase of surfactant concentration in the range of 4 to 9 times of CMC. The critical micellar aggregation numbers obtained by extrapolation method are half of the CTAB's (cetyltrimethylammonium bromide) which is hydrophobic with the same carbon number.