Polymer-like structure of lecithin reverse micelles in the lecithin+water+cyclohexane system

The lecithin reverse micelles with and without containing water in cyclohexane at 25.0 °C were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The molar mass M0 and hydrodynamic radius RH0 of the micelle determined at infinite dilution have increased with increasing water content W0, demonstrating that the micelles grow in mass and in size with water uptake into them. The values of RH0 as a function of M0 have been successfully analyzed with the use of the wormlike spherocylinder model. The results have revealed that the micelles with containing water assume a shape of rather flexible cylinders with the stiffness parameter λ−1=11.0 nm and the cross-sectional diameter d=5.2 nm. It is also found that the intermolecular distance between hydrophobic tails of two adjacent lecithin molecules on the micellar surface is about 1.2 nm without regard to water content W0. The micellar growth with increasing lecithin concentration has also been found to occur accompanying the structural evolution by combining information from SLS and DLS results.