Synthesis and Monolayer Behaviors of Succinic Acid-Type Gemini Surfactants Containing Semifluoroalkyl Groups
Year: 2016
Journal: J. Oleo Sci.
Authors: Kawase, T; Nagase, Y; Oida, T
In this work, novel succinic acid-type gemini surfactants containing semifluoroalkyl groups, dl- and meso-2,3-bis[Rf-(CH2)(n)]-succinic acids (Rf = C4F9, C6F13, C8F17; n = 2, 9), were successfully synthesized, and the effects of RI, methylene chain length (n), and stereochemistry on their monolayer behaviors were studied. Critical micelle concentrations (CMC) of dl- and meso-2,3-bis[C4F9(CH2)(9)]-succinic acids were one order of magnitude smaller than that of the corresponding 1+1 type surfactant, C4F9(CH2)(9)COOH. From surface pressure-area (pi-A) measurements, the lift-off areas of the geminis were found to decrease in the order C4F9 >= C6F13 >= C8F17, regardless of methylene chain length and stereochemistry. The zero-pressure molecular areas of the geminis were twice those of the corresponding 1+1 type surfactants. Based on Gibbs compression modulus analysis, it was clarified that 2,3-bis[C8F17(CH2)]-succinic gemini with short methylene chains (n = 2) would form more rigid monolayers than those having long methylene chains (n = 9). Unlike for 2,3-bis(alkyl)-succinic acids, the effects of stereochemistry on the monolayer behavior of semifluoroalkylated geminis were small.
