Formation of Multilamellar Vesicles by Oscillatory Shear

The formation of multilamellar vesicles (MLVs) from the lamellar phase of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in brine can be controlled by steady, oscillatory shearing. Increasing stress amplitude or decreasing frequency leads to more rapid onion formation. The formation kinetics can be scaled onto constant controlled shear stress experiments; this scaling demonstrates that a minimum strain amplitude of ∼14 that is independent of frequency is required for onion formation. Further, the ratio of deformation driving onion formation to the reversible, elastic deformation can be predicted from the loss tangent. The final size of the MLVs decreases with the stress amplitude, independent of frequency, in quantitative agreement with MLVs formed under steady, applied shear stress.