Organization of Amphiphiles, Part 1: Evidence in Favor of Pre-micellar Aggregates through Fluorescence Spectroscopy

Abstract

Abstract The advantage of a change in the vibrational structure of the emission spectra of pyrene as a function of the concentration of a series of polyoxyethylated alkyl ethers and alkylsulfonates has been utilized to explore the co-operative association of ionic and nonionic amphiphiles into micelles, the micropolarity of these micelles and the solubilization site of pyrene in micelles. The results indicate that the micropolarity of the environment experienced by pyrene is alcohol-like. Pyrene preferably resides in the palisade layer of a nonionic micelle, while in the interior of an anionic micelle. A multiple equilibrium model for micelle formation has been suggested and the existence of pre-micellar aggregates has been evidenced from the excimer characteristics of pyrene.