Viscoelasticity and Interface Bending Properties ofLecithin Reverse Wormlike Micelles Studied by Diffusive Wave Spectroscopyin Hydrophobic Environment.

Upon the addition of minute quantitiesof water into a phosphatidylcholine(PC) solution in certain organic solvents, PC micelles elongate intogiant reverse wormlike micelles that entangle and form highly viscousmicroemulsions, called lecithin organogels. We investigated the microrheologicalproperties of concentrated PC–cyclohexane reverse wormlikemicellar systems by diffusive wave spectroscopy (DWS) in apolar medium,combined with bulk shear rheology. We applied DWS to our oil-continuoussystem by using hydrophobic poly(hydroxystearic acid)-grafted PMMAparticles as monodisperse tracer particles. Relevant parameters suchas the micellar scission energy and persistence length were extractedfrom the microrheology data and interpreted according to the sphere-to-rod-to-spherestructural transition. On the basis of these quantities, we calculatedthe bending and saddle-splay moduli of the PC-covered water–cyclohexaneinterface. This approach represents a new method for the quantitativeestimation of these fundamental parameters, which are thought to underpinthe self-assembly of surfactants. [ABSTRACT FROM AUTHOR]