Characterizing Aqueous Micellar Triton X-100 Solutions of a Fluorescent Model Triglyceride

Abstract

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.