Abstract
Supercritical CO2 (scCO2) is non-polar and has weak van der Waals forces, hence it is not suitable for dissolving polar substances. This disadvantage has limited its application in chemical processes such as separation, reaction, and materials synthesis. One of the most promising approaches for enhancing solubility of polar substances in scCO is to form reversed micelles with high-polarity aqueous cores in the continuous scCO2 phase, that is, a water-in-scCO2 microemulsion (W/CO2μE). Since such an organized fluid has the attractive characteristics of scCO2 as well as the solvation properties of bulk water, it is expected to behave as a universal solvent. For example, a W/CO2μE will hopefully be a volatile organic compound (VOC) -free and energy-saving solvent for nano-material synthesis, enzymatic reactions, dry-cleaning, dyeing, preparation of inorganic/organic hybrid materials, and so on. To be a viable green technology, the amount of surfactant used for those applications should be as small as possible, and one approach to decrease the amount is to develop surfactants with higher solubilizing powers.
This review is introducing (1) a good solubilizer for a W/CO2μE, (2) phase behavior and nano-structure of the W/CO2μE, and its industrial applications.
