Characterizing aqueous micellar Triton X-100 solutions of a fluorescent model triglyceride

We report the synthesis and characterization of a model grease triglyceride in which one of the fatty-acid chains is replaced with a pyrenylbutyrate group. This substance 1 can be solubilized in water in the presence of excess Triton X-100, a nonionic surfactant. At high concentrations of surfactant (>10 cmc) the system forms solutions with a Poisson distribution of 1 in the surfactant micelles. Fluorescence decay measurements allow the mean occupancy ([n] = [1]/[micelle]) and the micelle aggregation number (N-ag = 100 +/- 5) to be determined. Despite its large size, 1 does not affect N-ag. As these solutions are diluted with water, the ratio of the excimer-to-monomer intensities I-E/I-M increases, and in this concentration range, both I-E/I-M and [n] scale as [surfactant](2). Solutions diluted below the cmc of the surfactant itself yield stable emulsions of aggregates of 1. Excitation spectra confirm that, within these aggregates, 1 is present as an amorphous fluid, rather than a microcrystalline solid.