The adsorption of undecanoic acid and non-adecanoic acid on oxidized and unoxidized copper crystals

Electron microscopy and electron diffraction were used in conjunction with a radioactive tracer to investigate experimentally the adsorption of undecanoic acid and nonadecanoic acid from cyclohexane solution on the carefully characterized (100), (110), (111), and (311) faces of copper and oxidized copper crystals. Nonadecanoic acid was isotropically adsorbed on the copper crystal with the molecules virtually perpendicular to the adsorbent in islands. As the adsorption continued, these islands grew laterally until after about 64 hrs. a continuous monolayer was formed. The equivalent of a monolayer of undecanoic acid was absorbed on the copper crystal after about 64 hr., but the (100) face adsorbed more of this acid than either of the other three faces for adsorption times less than 17 hrs. The (100) face was roughened the most by oxidation, and this face of the oxidized crystal was outstanding in its adsorption of both acids. The equivalent of a monolayer of undecanoic acid that followed the irregularities of the surface was not adsorbed after 128 hr. on any of the faces of the oxidized crystal. Approximately the equivalent of a monolayer of nonadecanoic acid was adsorbed after 1 min. on the oxidized surface, but the adsorbate rapidly desorbed into the solution.