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Effects of Degassing on the Long-Range Attractive Force between Hydrophobic Surfaces in Water

Summary: Effects of Degassing on the Long-Range Attractive Force
between Hydrophobic Surfaces in Water
Hallam Stevens,§ Robert F. Considine,| Calum J. Drummond,*,
Robert A. Hayes, and Phil Attard*,
CSIRO Molecular Science, P.O. Box 184, North Ryde New South Wales 1670, Australia,
School of Chemistry F11, University of Sydney, New South Wales 2006, Australia, Department
of the History of Science, Harvard University, Science Center 371, Cambridge, Massachusetts
02138, Barwon Water, Post Office Box 659, Geelong Victoria 3220, Australia, and Philips
Research Laboratories, Professor Holstlaan 4 (WY72) 5656 AA Eindhoven, The Netherlands
Received March 21, 2005. In Final Form: April 20, 2005
The long-ranged attractions between hydrophobic amorphous fluoropolymer surfaces are measured in
water with and without dissolved air. An atomic force microscope is used to obtain more than 500 measured
jump-in distances, which yields statistically reliable results. It is found that the range of the attraction
and its variability is generally significantly decreased in deaerated water as compared to normal, aerated
water. However, the range and strength of the attraction in deaerated water remain significantly greater
than the van der Waals attraction for this system. The experimental observations are consistent with
(1) nanobubbles being primarily responsible for the long-ranged attraction in normal water, (2) nanobubbles
not being present in deaerated water when the surfaces are not in contact, and (3) the attraction in the
of the type identified by Be´rard et al. [J. Chem. Phys. 1993, 98, 7236]. It is argued that the measurements


Source: Attard, Phil - School of Chemistry, University of Sydney


Collections: Chemistry