Complex Formation of Semifluorinated (gamma)-Cyclodextrin and Surfactants in Liquid Carbon Dioxide

(gamma)-Cyclodextrins functionalized at the 6-position with perfluoro butanoate groups were prepared from the esterification reaction between (gamma)-cyclodextrin and perfluorobutanoic acid. The semifluorinated (gamma)-cyclodextrin derivatives exhibited amphiphilic behavior and an apparent solubility in densified CO2. They can form soluble complexes with surfactants such as bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and N-lauroylsarcosine sodium salt in liquid CO2. The complex with AOT was confirmed visually and by differential scaning calorimetry (DSC), which did not show the characteristic melting endotherm of AOT. The formation of complexes of the single-tail surfactant N-lauroylsarcosine sodium salt and (gamma)-cyclodextrins was also investigated.