title: Polymorphism of natural fatty acid liquid crystalline phases.
abstract: We study the phase behavior in water of a mixture of natural long chain fatty acids (FAM) in association with ethylenediamine (EDA) and report a rich polymorphism depending on the composition. At a fixed EDA/FAM molar ratio, we observe upon dilution a succession of organized phases going from a lamellar phase to a hexagonal phase and, finally, to cylindrical micelles. The phase structure is established using polarizing microscopy, SAXS, and SANS. Interestingly, in the lamellar phase domain, we observe the presence of defects upon dilution, which SAXS shows to correspond to intrabilayer correlations. NMR and FF-TEM techniques suggest that these defects are related to an increase in the spontaneous curvature of the molecule monolayers in the lamellae. ATR-FTIR spectroscopy was also used to investigate the degree of ionization within these assemblies. The successive morphological transitions are discussed with regards to possible molecular mechanisms, in which the interaction between the acid surfactant and the amine counterion plays the leading role.
authors: Université de Bordeaux, Centre de Recherche Paul Pascal, UPR CNRS 8641, 115 avenue Schweitzer, 33600 Pessac, France.
authors: Hélène
authors: H
authors: Fay
authors: Steven
authors: S
authors: Meeker
authors: Juliette
authors: J
authors: Cayer-Barrioz
authors: Denis
authors: D
authors: Mazuyer
authors: Isabelle
authors: I
authors: Ly
authors: Frédéric
authors: F
authors: Nallet
authors: Bernard
authors: B
authors: Desbat
authors: Jean-Paul
authors: JP
authors: Douliez
authors: Virginie
authors: V
authors: Ponsinet
authors: Olivier
authors: O
authors: Mondain-Monval
mesh_terms: D003460:Crystallization; D005227:Fatty Acids / Q000737:chemistry*; D005614:Freeze Fracturing; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D012542:Scattering, Radiation
chemical_list: D005227:Fatty Acids