Sagisaka Masanobu, Koike Daisuke, Yoda Satoshi, Takebayashi Yoshihiro, Furuya Takeshi, Yoshizawa Atsushi, Sakai Hideki, Abe Masahiko, Otake Katsuto
Department of Materials Science and Technology, Faculty of Science and Technology, Hirosaki University, Bunkyo-cho 3, Hirosaki, Aomori 036-8561, Japan.
Langmuir. 2007 Aug 14;23(17):8784-8. doi: 10.1021/la700564z. Epub 2007 Jul 18.
The effect of surfactant tail structure on the stability of a water/supercritical CO2 microemulsion (W/scCO2 muE) was examined for various fluorinated double-tail anionic surfactants of different fluorocarbon chain lengths, F(CF2)n (n = 4, 6, 8, and 10), and oxyethylene spacer lengths, (CH2CH2O)(m/2) (m = 2 and 4). The phase behavior of the water/surfactant/CO2 systems was studied over a wide range of CO2 densities from 0.70 to 0.85 g/cm(3) (temperatures from 35 to 75 degrees C and pressures up to 500 bar) and corrected water-to-surfactant molar ratios (W0c). All of the surfactants yielded a W/scCO2 muE phase, that is, a transparent homogeneous phase with a water content larger than that permitted by the solubility of water in pure CO2. With increasing W0c, a phase transition occurred from the muE phase to a macroemulsion or a lamella-like liquid crystal phase. The maximum W0c value was obtained at a tail length of 12-14 A, indicating the presence of an optimum surfactant tail length for W/scCO2 muE formation.
研究了表面活性剂尾部结构对水/超临界二氧化碳微乳液（W/scCO2 muE）稳定性的影响，该微乳液使用了不同碳氟链长度F(CF2)n（n = 4、6、8和10）以及不同氧化乙烯间隔长度(CH2CH2O)(m/2)（m = 2和4）的多种氟化双尾阴离子表面活性剂。在0.70至0.85 g/cm³的广泛二氧化碳密度范围（温度为35至75摄氏度，压力高达500巴）以及校正后的水与表面活性剂摩尔比（W0c）下，研究了水/表面活性剂/二氧化碳体系的相行为。所有表面活性剂都产生了W/scCO2 muE相，即一种透明均相，其含水量大于水在纯二氧化碳中的溶解度所允许的量。随着W0c的增加，发生了从微乳液相到宏观乳液或层状液晶相的相变。在尾部长度为12 - 14 Å时获得了最大W0c值，表明存在形成W/scCO2 muE的最佳表面活性剂尾部长度。
