Fluorescence Investigation of Aggregation Behaviors of Novel Anionic Gemini Surfactants

Steady-state fluorescence and fluorescence quenching measurements have been carried out to investigate the aggregation behavior for four novel alkylbenzene sulfonate gemini surfactants Ib, Ic, Id, and Ie in aqueous solutions at 298.15 K. Some important micellar parameters critical micelle concentration (cmc), aggregation number (N) and micropolarity are obtained. It is found that the cmc values (cmcc) for the studied gemini surfactants determined by fluorescence quenching measurement are in agreement with the results reported previously by the surface tension measurement or the method using pinacyanol. The aggregation number of surfactant Ie is smaller than those of Ib, Ic and Id. It is explained by the formation of premicellar aggregates inhibiting the formation of micelles due to the increasing hydrophobic portion of the gemini surfactants. Furthermore, the values of I 1/I 3 for four gemini surfactants are determined. It is shown that the decreases of I 1/I 3 stretch over a range of concentrations of more than one decade. And it is given the information that the micropolarity in the four gemini surfactant micelles sensed by pyrene is relatively high.