Demicellization of sodium perfluorooctanoate and dodecyl sulfate mixtures revealed by pyrene fluorescence quenching

The behavior of fluorocarbon and hydrocarbon quenchers toward pyrene fluorescence was informative as to not only the distribution of quenchers among micelles but also the microscopic micelle demixing. The slight differences of quenching extent between fluorocarbon and hydrocarbon quenchers were observed to come from the deviation from Poisson distribution of fluorocarbon quenchers among hydrocarbon micelles. The intermicellar statistical distribution of quenchers could be influenced by the low affinity between fluorocarbon and hydrocarbon chains. The lost quenching of pyrene was observed due to the separated solubilization of pyrene and fluorocarbon quencher into two types of mixed micelles. However, the differences of quenching extent between fluorocarbon and hydrocarbon quenchers became small for sodium perfluorooctanoate-dodecyl sulfate mixtures at high concentration and temperature. The mutual miscibility in a micelle increased due to the increase of the micelle size under high surfactant concentrations and the heat of mixing at high temperature. The pyrene fluorescence quenching method using fluorocarbon quencher was effective way to-indicate the demicellization phenomenon.