title: Surfactant-mixing effects on the interfacial tension and the microemulsion formation in water/supercritical CO2 system.
abstract: The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.
authors.affiliation: Department of Materials Science and Technology, Faculty of Science and Technology, Hirosaki University, Bunkyo-cho 3, Hirosaki, Aomori 036-8561, Japan. sagisaka@cc.hirosaki-u.ac.jp
authors.forename: Masanobu
authors.initials: M
authors.lastname: Sagisaka
authors.forename: Tatsunori
authors.initials: T
authors.lastname: Fujii
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koike
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoda
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takebayashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Furuya
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yoshizawa
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abe
authors.forename: Katsuto
authors.initials: K
authors.lastname: Otake