Solvation environment provided by self-assembling aqueous sodium oleate+1-octanol small unilamellar vesicles

Self-assembling vesicles composed of aqueous sodium oleate and 1-octanol are prepared by simple mixing and analyzed with fluorescence probes pyrene, 1,3-bis(1-pyrenyl)propane, Nile Red, dansylamide, and 1-pyrenecarboxaldehyde, and absorbance probe Reichardt's betaine dye. Reichardt's dye locates itself in the interfacial region of the vesicles. In that cybotactic region it reports a solvation environment similar to ethanol. Pyrene locates deeper to the center of the lipid bilayer in an extremely nonpolar environment. 1-Pyrenecarboxaldehyde resides in the stable interfacial region and reports a static dielectric constant comparable to that of ethanol. 1,3-Bis(1-pyrenyl)propane indicates an extremely high microviscosity in the cybotactic region of the probe. Nile Red initially shows a variable Stokes shift, but eventually locates in the interfacial region and exhibits a microenvironment similar to a short-chain alcohol. Dansylamide shows similar results. A comparison with micellar aqueous sodium dodecylsulfate indicates that the solvation microenvironment afforded by these novel self-assembling vesicles is significantly less dipolar and more viscous.