Synthesis and surface activities of organic solvent-soluble fluorinated surfactants

A variety of fluorinated surfactants soluble in organic solvent were prepared, including C8F17SO2NHCnH2n+1 (n = 2, 4, 6, 8, 10), C8F17SO2NHR (R = C6H11, C6H5), C8F17SO2N(CnH2n+1)2 (n = 1, 2, 3, 4) and C8F17SO2NH(CH2)nNHO2SC8F17 (n = 6, 10). Their surface activities in various organic solvents were determined by surface tension measurement. The results showed that these fluorinated surfactants can reduce the surface tension of both polar and non-polar organic solvents. In general, organic solvents with strong polarity or long alkyl chain are beneficial to increase the surface activity of these polar fluorinated surfactants. By comparing fluorinated surfactants with the same fluorocarbon segment and connecting group, C8F17SO2N(CnH2n+1)2 (n = 1, 2, 3, 4) showed lower surface activity in organic solvents than C8F17SO2NHCnH2n+1 (n = 2, 4, 6, 8) with an equal carbon number of the solvophilic group. Through surface tension vs. concentration curves given for N-octyl perfluorooctanesulfonamide in various organic solvents, a break point like the critical micelle concentration of ordinary surfactants in aqueous solutions was observed, and the effect of the different types of organic solvents on adsorption and aggregation behavior was also studied.