The synthesis and surface activity of perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid ester fluorocarbon surfactants

A series of perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid ester fluorocarbon surfactants, CF3CF2CF2OCF(CF3)CF2OCF(CF3)COOCnH2n+1 (C9F17O4–CnH2n+1: n = 8, 12, 16, 18), were synthesized by esterification of 2,3,3,3-tetrafluoro-2-(1,1,2,3,3,3-hexafluoro-2-(heptafluoropropyloxy)-propoxy)-propionic acid fluoride with 1-octanol, 1-dodecanol, 1-hexadecanol and 1-octadecanol, respectively. The structures of C9F17O4–CnH2n+1 (n = 8, 12, 16, 18) were extensively characterized by FT-IR, 1H NMR and 19F NMR. The results of study on the surface activities show they have low surface tension and can significantly reduce the surface tensions of organic solvents by 40–83%. Besides, the critical micelle concentrations of these surfactants in solvents with different polarities have been identified at 18 °C. Furthermore, the surface excess concentrations and the effective cross-section areas of C9F17O4–CnH2n+1 in cyclohexane have been analyzed in detail. The arrangements of these surfactants at the air/solvent interface were speculated thereby.