Determination of micellar aggregation numbers of dimeric quaternary ammonium surfactant by steady-state fluorescence probe method

The micelle aggregation numbers(N) and critical micelle concentrations(cmc) of dimeric quaternary ammonium (DQA) surfactant were determined by steady-state fluorescence probe method with pyrene and cetylpuridinium chloride(CPC) as fluorescence probe and quencher, respectively. According to the change of fluorescence intensity ratio of pyrene I_(373)/I_(383) with the change of surfactant concentration in aqueous solution. The determination value of cmc of DQA is 0. 711 mmol·L~(-1) in the saturated aqueous solution of pyrene at 25℃. The critical micelle concentration (cmc) was investigated by steadystate fluorescence probe and compared with that determined by surface tension method. The aggregation numbers increase linearly with the concentration of DQA surfactant at 25℃when the concentration of DQA is in range of 4～8 times of cmc together with 0.16～0. 24 mmol·L~(-1) of CPC.The critical micelle aggregation number (N_m) is 10. 27 when the concentration of DQA is equal to cmc. The micelle aggregation numbers is slightly increased with the rise of temperature in the arange of experimental temperature.