Critical vesiculation concentration

Some surfactants self-assemble into closed bilayers called vesicles (or liposomes when formed from phospholipids). Vesicles are often spherical but can take other shapes and can be unilamellar or multilamellar. In contradistinction to micelles, vesicles may not be thermodynamically stable. Another important difference between vesicles and micelles is that vesicles have an inside that encloses some of the aqueous phase and an outside. The existence of a critical vesiculation concentration, above which some surfactants would form vesicles, is sometimes mentioned. This is probably incorrect. At very low concentrations, surfactants always start forming micelles that may turn into vesicles ct higher concentrations. Given in Fig. I are schematic representations of a micelle and a vesicle, both o f spherical shape. 

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