Fluorescence lifetime imaging microscopy (FLIM) reveals vesicle sizes, structures, microenvironments, and reagent partitionings for widely used surfactant–water systems under conditions relevant to organic synthesis. In contrast to previous investigations, the present systems use surfactants and a representative organohalide substrate at the high concentrations that are reflective of the preparative-scale organic reactions performed and reported in water (e.g., oxidative addition to metal powders, catalytic carbon–carbon bond forming cross-coupling reactions). In the presence of a representative organic substrate, 2-iodoethylbenzene, micelles swell into vesicles that are up to 20 µm in diameter, which is four orders of magnitude larger than previously measured in the absence of organic substrate (5–200 nm). The partitionings of reagents in these systems are imageable through FLIM—demonstrated here with nonpolar, amphiphilic, organic, basic, oxidative-addition reactive compounds and a metal powder. Further, FLIM characterizes the chemical species comprising the microenvironments inside micelles and vesicles, showing that surfactants cause a range of different microenvironments inside smaller micelles (&lt;200 nm), but that addition of a representative organic substrate produces a more uniform internal environment upon swelling to larger vesicles, with microenvironments dictated primarily by the high concentration of the substrate rather than by the surfactant. Together, these data provide immediately actionable information for revising previous reaction models of surfactant–water systems that underpin sustainable organic chemistry.

Surfactant micellar and vesicle microenvironments and structures under synthetic organic conditions

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