Determination of Critical Micellar Aggregation Numbers of Quaternary Ammonium Gemini Surfactants Containing Modified Rosin by Steady-State Fluorescence Probe Method

Critical aggregation numbers of micelle(Nm) of quaternary ammonium gemini surfactants containing modified rosin,DDMPDAB,DDMHPDAC,and DDMHDAB,were determined by steady-state fluorescence probe method in which pyrene was used as the fluorescence probe and cetylpyridinium chloride(CPC) as the quencher.According to the change of fluorescence intensity ratio of pyrene I1/I3 with the change of surfactant concentration of aqueous solution,critical micelle concentration(CMC) was investigated by steady-state fluorescence probe and compared with that determined by surface tension method.The results showed that CMC determined by steady-state fluorescence probe was in agreement with that determined by surface tension method.CMC values for DDMPDAB,DDMHPDAC and DDMHDAB were 2×10-5,8×10-5 and 6×10-5 mol/L,respectively.Satisfactory results were obtained when the surfactant solution was prepared with saturated aqueous solution of pyrene and the optimum concentration of CPC was selected at 0.04～0.06 mmol/L.The experimental results showed that N increased linearly with the increase of the surfactant concentration in a range of 5～15 times CMC and Nm can be extrapolated from the N—C curve,which were 10,19,and 20,respectively.