Synthesis of ether-linked fluorocarbon surfactants and their aggregational properties in organic solvents
A series of single- and double-tailed hydrocarbon–fluorocarbon (HF) surfactants were prepared to evaluate the effect of molecular structure on aggregate formation in organic solvents. The molecules were designed with ether linkages to permit facile syntheses of both sets of molecules. Solvent foaming studies were used to rapidly assess the surface-active properties of the surfactants, while dynamic light scattering provided quantitative critical micelle concentrations (CMC) and hydrodynamic radius (Rh) measurements of the aggregates in solution. The single-tailed surfactants did not produce any foaming action in a number of hydrocarbon solvents, nor was any micellar formation observed up to 100 mM concentrations. Double-tailed surfactants, on the other hand, gave low CMC values in dodecane but with Rh values that indicated a tight micelle structure. Bilayer formation was expected but not observed for these molecules, which is believed to be due to their unusual structural geometry, imparted by the glycerol backbone. No thermotropic liquid crystalline (LC) behavior was observed for any of the single- or double-tailed molecules. These data contrast with the known behavior of perfluorinated alkanes and other fluorinated surfactants, suggesting that the ether linkage plays an important role in the self-organizing behavior of these molecules.