Change of molecular packing and orientation from monolayer to multilayers of hydrogenated and fluorinated carboxylates studied by in-plane X-ray diffraction together with NEXAFS spectroscopy at C K-edge

By applying the in-plane X-ray diffraction together with the NEXAFS spectroscopy to organized molecular films, the molecular orientation and packing from the monomolecular layers to multilayers of hydrogenated and fluorinated long-chain carboxylic acids and carboxylates were characterized. The two-dimensional molecular packing in the monolayers for cadmium salts of fatty acids was clearly different from those for fatty acids as well as those in the multilayers, whereas the fluorinated long-chain carboxylates had hexagonal packing of the rod like molecules common in both mono- and multilayers. This seems to be probably due to difference of molecular cohesive energy between hydrocarbons and fluorocarbons themselves.