Micellar immiscibility of lithium 1,1,2,2-tetrahydroheptadecafluorodecyl sulfate and lithium tetradecyl sulfate mixture

We examined the immiscibility of fluorocarbon and hydrocarbon surfactants having the same head groups, i.e., lithium 1,1,2,2-tetrahydroheptadecafluorodecyl sulfate (LiHFDeS) and lithium tetradecyl sulfate (LiTS). The micellar pseudophase diagram was determined by conductivity and fluorescence quenching methods. The coexistence of two kinds of micelles has been demonstrated by the fluorescence quenching of pyrene with a fluorocarbon quencher. Pyrene is located in LiTS-rich micelles, and its fluorescence is quenched by micelle-solubilized quenchers. However, the pyrene fluorescence is hardly quenched by a fluorocarbon quencher when a second type of micelle rich in fluorocarbon surfactant appears. The collision probability between the fluorocarbon quencher and pyrene will be small within the lifetime of the excited pyrene because the fluorocarbon quencher and pyrene are separately solubilized in LiTS-rich and LiHFDeS micelles, respectively. The effect of addition of salt on the depression of quenching was also examined.