title: A new reverse wormlike micellar system: mixtures of bile salt and lecithin in organic liquids.
abstract: We report a new route for forming reverse wormlike micelles (i.e., long, flexible micellar chains) in nonpolar organic liquids such as cyclohexane and n-decane. This route involves the addition of a bile salt (e.g., sodium deoxycholate) in trace amounts to solutions of the phospholipid lecithin. Previous recipes for reverse wormlike micelles have usually required the addition of water to induce reverse micellar growth; here, we show that bile salts, due to their unique "facially amphiphilic" structure, can play a role analogous to that of water and promote the longitudinal aggregation of lecithin molecules into reverse micellar chains. The formation of transient entangled networks of these reverse micelles transforms low-viscosity lecithin organosols into strongly viscoelastic fluids. The zero-shear viscosity increases by more than 5 orders of magnitude, and it is the molar ratio of bile salt to lecithin that controls the viscosity enhancement. The growth of reverse wormlike micelles is also confirmed by small-angle neutron scattering (SANS) experiments on these fluids.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742-2111, USA.
authors.forename: Shih-Huang
authors.initials: SH
authors.lastname: Tung
authors.forename: Yi-En
authors.initials: YE
authors.lastname: Huang
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Raghavan
mesh_terms: D001647:Bile Acids and Salts / Q000737:chemistry*; D003510:Cyclohexanes / Q000737:chemistry; D008823:Micelles; D009930:Organic Chemicals / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*
chemical_list: D001647:Bile Acids and Salts; D003510:Cyclohexanes; D008823:Micelles; D009930:Organic Chemicals; D010713:Phosphatidylcholines; C506365:Cyclohexane