CO₂ enables 'switchable surfactants'

Being able to reversibly generate stable emulsions could help facilitate syntheses, separations, and processing of a variety of chemicals. Philip G. Jessop of Queen's University, Kingston, Ontario, and his colleagues have made this possible by creating "switchable surfactants" that need only CO₂ and air to turn on and off (Science 2006, 313, 958). A year ago, Jessop's group reported switchable solvent systems based on the same concept (C&EN, Aug. 29, 2005, page 27). The researchers used long-chain alkylamidines RN=CR'-NR'₂, where R is C₁₂H₂₅ or C₁₆H₃₃ and R' is methyl—that form bicarbonate salts when mixed with water and CO₂ is added. The in situ salt formation helps create stable emulsions. Bubbling air into the mixture releases CO₂ and breaks the emulsion. Switchable surfactants can be considered for all process applications involving surfactants, including emulsion polymerizations and different aspects of crude oil processing, Jessop notes.