Microemulsion formation, fluorinated

Microemulsion Formation with Fluorinated Phosphate Surfactants... 

The uses of fluorosurfactants to stabilize water-in-carbon dioxide (w/c) microemulsions are reviewed. A systematic study with fluorosuccinate surfactants of the effects of the extent of fluorination of hydrophobic chains on the stability and structures of these w/c phases is described. Therefore, it has been possible to delineate a structure-function relationship for these fluorosurfactants with reference to their efficiency of water-in-carbon dioxide microemulsion formation. An important finding is that one of these surfactants, namely sodium bis(l//,l//-perfluoropentyl)-2-sulfosuccinate (di-CF4), is able to stabilize w/c microemulsions close to the bottle pressure of a normal CO2 cylinder. Such efficient surfactants of this kind have obvious advantages for potential practical applications of CO2. 

So far we can generate supercritical carbon dioxide microemulsions with varying mi-crostructures under a pressure of p = 220 bar. The next step is to find appropriate surfactants for an efficient solubilisation of C02 as today over 48 wt.% surfactant is required to formulate a one-phase region in the system H20/NaCl-C02-Lutensol XL70 (see Fig.ll.3).Good amphiphilic candidates with C02 -philic parts are fluorinated surfactants. Once a more efficient surfactant has been identified, the formation of microemulsions under pressure has to be studied. 

None of the fluorinated surfactants was suitable for preparing oil-water microemulsions. Thoay concluded that fluorinated surfactants weaken the CH—CH interchain interaction essential for the formation of stable oil-water microemulsions. 

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