Self-assembly of fatty acids and hydroxyl derivative salts.
We report the dispersions of a fatty acid and hydroxyl derivative salts in aqueous solutions that were further used to produce foams and emulsions. The tetrabutyl-ammonium salts of palmitic acid, 12-hydroxy stearic acid, and omega-hydroxy palmitic acid formed isotropic solutions of micelles, whereas the ethanolamine salts of the same acids formed turbid birefringent lamellar solutions. The structure and dimension of those phases were confirmed by small-angle neutron scattering and NMR. Micelles exhibited a surprisingly small radius of about 20 A, even for hydroxyl fatty acids, suggesting the formation of hydrogen bonds between lipids in the core of the micelles. In the case of ethanolamine salts of palmitic and 12-hydroxy stearic acids, the lipids were arranged in bilayers, with a phase transition from gel to fluid upon heating, whereas for omega-hydroxy palmitic acid, monolayers formed in accordance with the bola shape of this lipid. Foams and emulsions produced from ethanolamine salt solutions were more stable than those obtained from tetrabutyl-ammonium salt solutions. We discuss these results in terms of counterion size, lipid molecular shape, and membrane curvature.
Novales
Bruno
B
UR1268, Biopolymères Interactions Assemblages, Institut National de la Recherche Agronomique, Equipe Interfaces et Systèmes Dispersés, rue de la Géraudière, Nantes, France.
Navailles
Laurence
L
Axelos
Monique
M
Nallet
Frédéric
F
Douliez
Jean-Paul
JP
D004655:Emulsions; D019856:Ethanolamine / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry*; D006860:Hydrogen Bonding; D006900:Hydroxylation; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008858:Microscopy, Phase-Contrast; D019308:Palmitic Acid / Q000737:chemistry; D012492:Salts / Q000737:chemistry*; D012995:Solubility; D012996:Solutions / Q000737:chemistry*; D013229:Stearic Acids / Q000737:chemistry; D014867:Water / Q000737:chemistry
D004655:Emulsions; D005227:Fatty Acids; D008051:Lipid Bilayers; D008823:Micelles; D012492:Salts; D012996:Solutions; D013229:Stearic Acids; D014867:Water; D019308:Palmitic Acid; D019856:Ethanolamine