Abstract
Forces between the fuorocarbon monolayer surfaces were measured in the process of vapor saturation with the interfacial gauge. In vapors of ethanol or chloroform, for both liquids contact angles to the surface are finite (51° and 65°, respectively), the forces on approach showed long-range attraction, of which the range increased with time. These force profiles agree with the theory of capillary bridging mainly by constant volume meniscus. In the vapor of perfluorohexane, force profiles of a similar type as in the vapors of ethanol and chloroform were observed at the beginning of exposure to the vapor, while later the interaction changed to that for the meniscus in equilibrium with the vapor. After exposure of the surfaces to the vapor for more than I h and separating apart, discontinuous curves with an abrupt jump-in at 25 nm were observed on the following approach. Since perfluorohexane wets the fluorocarbon surface, the condensate spreads over the surfaces after breaking the meniscus. The force discontinuity is explained by the coalescence of two wetting films of perfluorohexane with a thickness of 8 nm. By fitting the measured force curves with theoretical forms, the condensate volumes and the acting values of relative vapor pressure were estimated and changes with time were considered.
Original language | English |
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Pages (from-to) | 5644-5650 |
Number of pages | 7 |
Journal | Langmuir |
Volume | 18 |
Issue number | 15 |
DOIs | |
Publication status | Published - 23 Jul 2002 |