title: Effect of perfluoroalkyl chain length on monolayer behavior of partially fluorinated oleic acid molecules at the air-water interface.
abstract: A series of oleic acid (OA) analogs containing terminal perfluoroalkyl groups (CF3, C2F5, n-C3F7, n-C4F9 or n-C8F17) was synthesized to clarify how the fluorinated chain length affects the stability and molecular packing of liquid-expanded OA monolayers at the air-water interface. Although the substitution of terminal CF3 group for CH3 in OA had no effect on monolayer stability, further fluorination led to a gradual increase in monolayer stability at 25 °C. Surface pressure-area isotherm revealed that partially fluorinated OA analogs form more expanded monolayers than OA at low surface pressures, and that the monolayer behavior of OA analogs with the even-carbon numbered fluorinated chain is almost the same as that of OA upon monolayer compression, whereas the behavior of OA analogs with the odd-carbon numbered fluorinated chain significantly differs from that of OA. These results indicate: (i) the terminal short part (at least C2 residue) in OA predominantly determines the liquid-expanded monolayer stability; (ii) the molecular packing state of OA may be perturbed by the substitution of a short odd-carbon numbered fluorinated chain; (iii) hence, OA analogs with even-carbon numbered chain are considered to be preferable as hydrophobic building blocks for the synthesis of fluorinated phospholipids.
authors.affiliation: Research Center of Advanced Bionics (RCAB), National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba 305-8565, Japan. t-baba@aist.go.jp
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Baba
authors.forename: Katsuki
authors.initials: K
authors.lastname: Takai
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takagi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kanamori
mesh_terms: D000388:Air; D054879:Halogenation; D006863:Hydrogen-Ion Concentration; D019301:Oleic Acid / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D019301:Oleic Acid
keywords: Equation of state; Equilibrium spreading pressure; Even/odd phenomenon; Fluorinated oleic acid; Monolayer stability; Surface pressure–area isotherm