As an alternative to toxic organic solvents, supercritical carbon dioxide (scCO₂) has attracted much attention over the last decade since it is nontoxic, inflammable, environmentally friendly, low cost and readily available in large quantities. With these advantages, together with its unique properties as a supercritical fluid such as adjustable solvent power, enhanced mass transfer characteristics and low surface tension, scCO₂ has prompted extensive research to develop scCO₂-based processes. Unfortunately, because CO₂ is nonpolar and has weak van der Waals forces, it is not suitable for dissolving polar substances; this fact has limited its application to processes such as separation, reaction, and material formation. One approach to overcoming this limitation is to employ specialized scCO₂ soluble surfactants that induce formation of reversed micelles with polar-solvent-cores (for example, water or ionic liquids) in the continuous scCO₂ phase. Since such systems would combine the attractive characteristics of scCO₂ with the solvating properties of polar solvents, those are expected to be a 'universal solvent'. This paper introduces studies for self-organization of surfactants in scCO₂, specially a W/CO₂ microemulsion.

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Ionic liquids are a class of organic electrolytes with melting points below 100°C. Owing to their unique and advantageous properties such as non-volatility, non-flammability, high thermal stability, and high electrochemical potential window, ionic liquids have currently received much attention for applications as novel solvents in many fields. The research interest related to ionic liquids is also growing in the field of colloid and interface chemistry. In this review, current trend in this area is overviewed, and the knowledge obtained to date regarding the self assembling behavior of surfactant molecules in ionic liquids is summarized stressing the micelle formation, liquid-crystalline mesophase formation, and cloud point phenomenon.

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