LONG-PERIOD STRUCTURE OF LANGMUIR-BLODGETT MULTILAYER ASSEMBLIES

The structures of cadmium eicosanoate (CdC220AC) and cadmium pentacosa -10,12-diynoate (Cd12-8AC) Langmuir-Blodgett multilayers were studied using x-ray structure analysis methods. The trial and error model refi nements indicated the fully ionized salts exist in a linear arrangemen t where the polar heads of the opposing monolayers are ionically bound with the cadmium ion nested between the carboxylates. The molecular o rientation of CdC20AC was found to be normal to the substrate, whereas Cd12-8AC was inclined by about 30 degrees to accommodate the diacetyl ene moiety. A mechanism for the salt formation upon deposition was rat ionalized by considering the dissolved counter ions to be loosely boun d within the electric double layers of the floating and submerged/depo sited monolayers.