It has been known that the addition of bile salts into lecithin organosols induces the formation of reverse wormlike micelles and the worms are similar to long polymer chains which entangle each other to form viscoelastic solutions. In this study, we further investigated the effects of different bile salts and bile acids on the growth of lecithin reverse worms in cyclohexane and n-decane. We utilized rheological and small-angle scattering techniques to analyze the properties and structures of the reverse micelles. All the bile salts can transform the originally spherical lecithin reverse micelles into wormlike micelles and their rheological behaviors can be described by the single-relaxation time Maxwell model. However, their efficiencies to induce the worms are different. In contrast, bile acids can only induce short cylindrical micelles before phase separation that are not long enough to impart viscoelasticity. We used Fourier transform infrared spectroscopy to investigate the interactions between lecithin and bile salts/acids and found that different bile salts/acids employ different functional groups to form hydrogen bonds with lecithin. Such effects determine the relative positions of the bile salts/acids in the headgroups of lecithin and thus results in varying efficiencies to alter the effective critical packing parameter for the formation of wormlike micelles. This work highlights the importance of intermolecular interactions in molecular self-assembly.

Molecular interactions between lecithin and bile salts/acids in oils and their effects on reverse micellization

246th National Meeting (2013)

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