title: Water/supercritical CO2 microemulsions with mixed surfactant systems.
abstract: Phase behavior was investigated for water/supercritical CO 2 (W/scCO2) microemulsions stabilized with sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO) 2) mixed with various guest surfactants. Only for the mixtures with fluorocarbon-hydrocarbon hybrid anionic surfactants (FC6-HC n), the maximum water-to-surfactant molar ratio (W0(c)) was larger than that estimated from linear interpolation of the W0(c) values for pure 8FS(EO) 2 and pure guest surfactant. Fourier transform infrared (FT-IR) measurement for the microemulsion revealed that the mixing of 8FS(EO) 2 with FC6-HC n can prevent a phase transition from the microemulsion to the liquid crystal even in the presence of excess water. It was also found from the measurement of water/scCO 2 interfacial tension that the area occupied per surfactant molecule was markedly increased by the mixing with FC6-HC n. The loose molecular packing, probably due to a microsegregation of 8FS(EO) 2 and FC6-HC n, is consistent with the enhanced stability of the microemulsion upon surfactant mixing.
authors: Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori, Japan. sagisaka@cc.hirosaki-u.ac.jp
authors: Masanobu
authors: M
authors: Sagisaka
authors: Daisuke
authors: D
authors: Koike
authors: Yasuaki
authors: Y
authors: Mashimo
authors: Satoshi
authors: S
authors: Yoda
authors: Yoshihiro
authors: Y
authors: Takebayashi
authors: Takeshi
authors: T
authors: Furuya
authors: Atsushi
authors: A
authors: Yoshizawa
authors: Hideki
authors: H
authors: Sakai
authors: Masahiko
authors: M
authors: Abe
authors: Katsuto
authors: K
authors: Otake