Donald S. Bethune, Gerard Meijer, et al.
Chemical Physics Letters
Preparation and characterization of Langmuir-Blodgett films of a geminally branched lipid acid have been achieved for the first time. Pressure-area isotherms of cadmium α,α-dimethylarachidate (2,2-dimethyl-1-eicosanoate) exhibit two condensed phases, one at an area consistent with a single layer expanded somewhat from cadmium arachidate by the methyl groups, the other at a much smaller area which could be consistent with trilayer formation. The isotherms are quite distinct considering the discontinuity in packing expected a priori by the presence of the geminal dimethyl substitution. Transfer to a solid surface from the air-water interface was accomplished at the less condensed phase and the resulting films were characterized as a monolayer, slightly expanded relative to cadmium arachidate. This characterization was made by a combination of two techniques: attenuated total internal reflectance shifts in the excitation of surface plasmons and electron mean free path of escape from X-ray photoelectron spectroscopy; both techniques were required as neither alone gave complete understanding. Transfer at the more condensed phase produced a layer somewhat thicker than that produced at the less condensed phase, but not as thick as expected from film area; expansion upon transfer apparently occurred, and this prevents full characterization. However, the more condensed phase is reproducible and is apparently a stable phase. Preparation of the substituted arachidic acid by an unambiguous route and characterization of the monolayer assemblies using the two techniques are discussed. © 1983 American Chemical Society.
Donald S. Bethune, Gerard Meijer, et al.
Chemical Physics Letters
Herbert C. Brown, Jin Soon Cha, et al.
Journal of Organic Chemistry
D. Johannsmann, F.W. Embs, et al.
Makromolekulare Chemie. Macromolecular Symposia
J.F. Rabolt, F.C. Burns, et al.
Journal of Electron Spectroscopy and Related Phenomena