Quartz crystal microbalance investigation of the structure of adsorbed soybean oil and methyl oleate onto steel surface

The adsorption behavior of soybean oil (SBO) and methyl oleate (MO) from hexadecane solvent onto a steel surface at room temperature was investigated using quartz crystal microbalance with dissipation (QCM-D). Adsorption of both SBO and MO in hexadecane increased with increasing concentration until a full surface coverage was attained. At full surface coverage, SBO and MO formed rigid films and achieved a concentration of 1.5 and 1.7 × 10−10 mol/cm2, respectively. Analysis of the QCM-D data determined that each formed a thin, rigid film where the thicknesses were approximately 1.5 nm for SBO and 7 Å for MO. The thicknesses indicate that the SBO adsorbed nearly perpendicular to the surface where MO molecules adsorbed nearly parallel to the surface.