Influence of Morphology on Polar Solvation Dynamics in Lecithin Reverse Micelles

Abstract

The continuous nonpolar phase can change the morphology of lecithin reverse micelles dramatically. In alkane solvents, increasing the hydration leads to gelation as isolated water droplets transform into an entangled tube network. In contrast, increasing the hydration for lecithin in benzene maintains isolated, largely spherical traditional reverse micelles. Solvation dynamics experiments have been carried out in the two different micellar environments. These measurements show that solvation dynamics are considerably more restricted in the tubular micelles than in the spherical droplets. This is interpreted as evidence for water pool formation and disorder at the interface in the spherical micelles and supports the hypothesis of substantial water incorporation into the tubular micelles. To perform solvation dynamics experiments in the benzene/lecithin/water reverse micelles, we have synthesized a new headgroup-labeled probe molecule. This synthesis, coupling the standard solvation dynamics probe, coumarin 343, to phosphatidylethanolamine through an amide bond, is presented.