Examination of adsorbed oleate layers at a fluorite surface by contact angle measurements and FT-IR/IRS spectroscopy
- Univ. of Utah, Salt Lake City, UT (United States)
Molecular layers of oleate at a fluorite crystal surface were prepared by spontaneous adsorption from alkaline aqueous solutions of sodium oleate. The adsorption density of such oleate layers was determined by Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS). Advancing and receding contact angles were measured for water drops on these carboxylate layers using the sessile-drop technique. The effect of surface heterogeneity (as established by the extent of oelate adsorption) on contact angle hysteresis for varying drop size is demonstrated. It was observed that both the contact angle hysteresis and contact angle/drop size relationship depend on the extent of deviation of the adsorbed layer from an ideal well-organzed organized monolayer. Experimental results support the position that it is of particular importance to examine both the advancing and receding contact angles with varying drop size whenever the sessile-drop technique is used to describe the nature of heterogeneous surfaces, including those prepared by adsorption of organic molecules. It was also found that the advancing contact angles for water drops are essentially the same for an equivalent level of adsorption of oleate and stearate at a fluorite surface. 62 refs., 7 figs.
- DOE Contract Number:
- FG03-93ER14315
- OSTI ID:
- 484487
- Journal Information:
- Langmuir, Vol. 13, Issue 5; Other Information: PBD: 5 Mar 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Wetting characteristics and stability of Langmuir-Blodgett carboxylate monolayers at the surfaces of calcite and fluorite
Oleate adsorption at an apatite surface studied by ex-situ FTIR internal reflection spectroscopy