| 초록 |
Emulsions consisting of the environmentally benign solvents carbon dioxide and water, which are nontoxic, nonflammable and inexpensive, may be substituted for toxic organic solvents in chemical processing. We report non-flocculated dilute water-in-CO2 (W/C) miniemulsions stablized for 24 hours with poly(1,1-dihydroperfluorooctyl methacrylate)-b-poly(ethylene oxide) (PFOMA-b-PEO) copolymers. The surfactants were synthesized by atom transfer radical polymerization with well-defined structure to achieve the proper hydrophilic-CO2-philic balance (HCB) and a low interfacial tension (~0.2 to 2 mN/m) between water and CO2. The average particle diameter, ranging from 70 to 140 nm, was measured with multiwavelength turbidimetry utilizing Mie theory, and the interfacial tension was measured with high pressure pendant drop tensiometry. The molar water/surfactant ratios reached 1170, in contrast with values of only about 5-60 for W/C microemulsions. The ability to stabilize much larger amounts of water in nanometer sized droplets with small amounts of surfactants is of great practical interest in reaction, separations and materials formation processes in CO2. |
