title: Micelle-vesicle transition of oleyldimethylamine oxide in water.
abstract: We studied the effects of the degree of ionization(alpha) and the surfactant concentration (C(d)) on the micelle-vesicle transition in salt-free oleyldimethylamine oxide (OlDMAO) aqueous solutions by the dynamic light scattering (DLS), the hydrogen ion titration, the small angle neutron scattering (SANS), the electrophoretic light scattering (ELS) and viscoelastic measurements. From the study of ionization effects, the micelle-vesicle transition was recognized as a change of aggregate size by the DLS measurement; however, the micelle-vesicle transition was not detected both in the ELS measurement and the hydrogen ion titration, suggesting that the electric properties of the worm-like micelles and the vesicles are very similar despite a large difference of shapes between them. From the results of the SANS, the DLS and the viscosity measurements, it was suggested that a concentration-dependent micelle-vesicle transition took place around C(p)=10 mmolkg-1 for the solutions at alpha=0.5. In the concentration-range 10 mmolkg-1<C(d)<150 mmolkg-1, the micelles and the vesicles coexisted. In the concentration region (C(d) = 10-50 mmolkg-1), the vesicle size increased with the surfactant concentration.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University 33, Hakozaki, Higashi-ku, Fukuoka 812- 858l, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Miyahara
authors.forename: Hideya
authors.initials: H
authors.lastname: Kawasaki
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Norio
authors.initials: N
authors.lastname: Nemoto
authors.forename: Rie
authors.initials: R
authors.lastname: Kakehashi
authors.forename: Shimon
authors.initials: S
authors.lastname: Tanaka
authors.forename: Masahiko
authors.initials: M
authors.lastname: Annaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maeda
mesh_terms: D004586:Electrophoresis; D008027:Light; D008823:Micelles; D009502:Neutrons; D009829:Oleic Acids / Q000737:chemistry*; D012542:Scattering, Radiation; D014867:Water / Q000737:chemistry*
chemical_list: D008823:Micelles; D009829:Oleic Acids; D014867:Water