Carbon dioxide/water, water/carbon dioxide emulsions and double emulsions stabilized with a nonionic biocompatible surfactant

摘要

Whereas microemulsions and emulsions of water and carbon dioxide have been reported for various surfactants with fluorocarbon surfactants, relatively few studies have been successful in forming these emulsions with hydrocarbon surfactants. Stable CO_2/water and water/CO_2 emulsions with droplets smaller than 1μm were formed at high shear with the nonionic surfactant polysorbate 80 (Tween 80). In order to understand the emulsion phase behavior at high shear, low shear phase behavior experiments were performed at the same temperature and pressure. For pressures up to 250bar and temperatures of 25-60°C, C/W emulsions were formed for water concentrations as low as 10%, as the surfactant is highly hydrophilic with limited CO_2-philicity. However, with added NaCl, the surfactant partitioned away from water toward CO_2, and W/C emulsions were formed with droplet sizes from a few 100nm to a few μm in diameter, which were stable for at least 24h. In addition C/W/C double emulsions are reported for the first time, as well as W/C/W/C triple emulsions. The ability to form emulsions with environmentally benign solvents, CO_2 and water, and biocompatible surfactants is desirable for green reaction and separation processes, as well as production of materials including pharmaceutical particles and composites.