Physical and electrochemical investigation of novel ultrathin films

A study of novel ultrathin films is presented in two sections. The first section presents an investigation of several unconventional film-forming molecules at the air/water interface using the surface film balance apparatus. Strongly hydrophobic fullerenes (C$ sb{60}$ and C$ sb{70}$) were found to spread at the air/water interface to form Langmuir films of multilayer rather than monolayer thicknesses. The formation of these well-defined multilayers is independent of the initial surface density of the fullerene. The films adopt discrete thicknesses of 4-5 monolayer equivalents. The multilayer of the non-spherical C$ sb{70}$ exhibited a transition attributed to a reorientational process that was not observed with the C$ sb{60}$ multilayer. A calculation of the work of compression for the two fullerene films confirmed important differences between the C$ sb{60}$ and C$ sb{70}$ films. 1,3,5- Phenylene-based hydrocarbon starburst dendrimers were also found to form multilayer Langmuir films at the air/water interface. The formation of these multilayers, however, is dependent on the initial surface density of dendrimer, and believed to rely upon interpenetration amongst dendrimer molecules. Langmuir-Blodgett films of dendrimer co-spread with fatty acid were examined by Atomic Force Microscopy. A series of amorphous polyimides also appear to form multilayer Langmuir films, possibly because they adopt a conformation on the water surface that renders them more rigid than in the bulk material.The second section describes the electrochemical and interfacial properties of two series of thiophene/ferrocene conjugates. The detailed electrochemistry of these compounds is described, including their electro-oxidative polymerization and the subsequent characterization of the polymer film. Their unique bifunctional nature leads to the formation of a polymer material that is intrinsically limited to the formation of monolayers. At the air/water interface, these molecules have a well-defined phase transition from a disordered state to an ordered state. Their oxidative polymerization was effected chemically at the air/water interface in both their expanded form, in which they are extended on the water surface, and a more condensed form, although it was observed to proceed more rapidly in the expanded form.In both studies, the properties of the ultrathin films that are formed are discussed in the context of the transition from aggregates to bulk material. The implication of the present results is also discussed with respect to the nature of the surface tension measurement in the surface film balance experiment. Finally, the importance of an architecture imposed by the properties of the molecules such as that observed in the electropolymerization of the thiophene/ferrocene compounds is discussed