SPONTANEOUS FORMATION OF REVERSE VESICLES

It was found that reverse vesicles are formed in a sucrose monoalkanoate/hexaethylene glycol hexadecyl ether (R16EO6)/hydrocarbon system in the absence of water. In the ternary system, a lamellar phase is formed in the sucrose alkanoate-rich region, whereas an isotropic liquid phase, containing reverse micelles, appears in the R16EO6 region. The aggregate shape depends on the sucrose alkanoate-to-R16EO6 ratio in the surfactant film, and a transition from reverse micelles to planar bilayers occurs with increasing content of sucrose alkanoate. Vesicles form in the two-phase region where a lamellar phase coexists with oil, containing solubilized R16EO6. Due to the high oil solubility of the R16EO6 surfactant, this coexistence region can be reached by diluting the reverse micellar phase with oil. Hence, a transition from reverse micelles to reverse vesicles can be generated by a simple oil dilution. This system displays strong analogies to the aqueous systems composed of a highly water soluble amphiphile, i.e., a bile salt, in addition to water and a lamellar-forming lipid, such as lecithin.