title: Water-Induced Phase Transition in Cyclohexane/n-Hexanol/Triton X-100 Mixtures at a Molar Composition of 1/16/74 Studied by NMR.
abstract: Molecular aggregation in a mixture of Triton X-100/n-hexanol/cyclohexane at a molar ratio of 1/16/74 is studied upon addition of small amounts of water. The composition of organic components has been chosen at a ratio n-hexanol/cyclohexane where a well-formed hydrogen bond network has been described. The ratio Triton X-100/n-hexanol has been chosen to afford a stoichiometry of ethylene oxide (EO) residues/n-hexanol of 1/2. At these conditions the addition of water consecutively produces the appearance of three defined phases: a clear solution, a lamellar phase, and a microemulsion. The two corresponding transitions occur at water/EO/n-hexanol molar ratios of 2/1/2 (clear to lamella), and 3/1/2 (lamella to microemulsion), while phase separation occurs at a molar ratio of 4/1/2, highlighting the important role of stoichiometry. Molecular dynamics measured by1H NMR techniques, such as DOSY, and calculations of T1and T2relaxation times allow distinguishing the transition between the different phases and justifying their structure. Molecular assembly in the three phases is organized around hydrogen bond networks in which the hydroxyl groups of both TX-100 and n-hexanol, ethylene oxide groups of TX-100, and water participate. 1D1H NMR spectral changes correlate with the different characteristics of the different phases. As the main characteristics of the lamellar phase we find a very restricted mobility of the molecules involved, and water chemical shifts in 1D1H NMR spectra of around 5.0 ppm, higher than that of bulk water appearing at 4.7 ppm.
authors.affiliation: Departamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile , Avenida Tupper 2069, Santiago 8370451, Chile.|Instituto de Ciencias Químicas, Facultad de Ciencias, Universidad Austral de Chile , Las Encinas 220, Valdivia 5090000, Chile.
authors.forename: Mario E
authors.initials: ME
authors.lastname: Flores
authors.affiliation: Departamento de Ciencia de los Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile , Avenida Tupper 2069, Santiago 8370451, Chile.
authors.forename: Francisco
authors.initials: F
authors.lastname: Martínez
authors.affiliation: Instituto de Ciencias Químicas Aplicadas, Facultad de Ingeniería, Universidad Autónoma de Chile , El Llano Subercaseaux 2801, Santiago 8320325, Chile.
authors.forename: Andrés F
authors.identifier: 0000-0001-8007-6264
authors.initials: AF
authors.lastname: Olea
authors.affiliation: Material Characterization Central Laboratory, School of Science and Engineering, Waseda University , 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Shibue
authors.affiliation: Material Characterization Central Laboratory, School of Science and Engineering, Waseda University , 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Natsuhiko
authors.initials: N
authors.lastname: Sugimura
authors.affiliation: Department of Applied Chemistry, School of Science and Engineering, Waseda University , 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nishide
authors.affiliation: Instituto de Ciencias Químicas, Facultad de Ciencias, Universidad Austral de Chile , Las Encinas 220, Valdivia 5090000, Chile.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Moreno-Villoslada