Reactions in Organized and Constricted Systems

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The ability of molecular cations to migrate and undergo chemical reactions will be determined in a variety of different environments including low viscosity liquids at room temperature, glasses at 77 K, and highly viscous oligomers and polymers. Polymers to be investigated range from chloropolymers such as polyvinylchloride to polystyrene and polyethylene. The cationic species will be generated by exposure of polycyclic hydrocarbons such as anthracene, naphthalene, and pyrene to high-energy radiation produced from a Fabretron. The resulting cationic species will be detected by transient spectroscopy on a picosecond time scale. In addition to the kinetic analysis of the cation migration rate, an investigation of the rate of fluorescence quenching of both absorbed and surface bound pyrene at solid-air and solid-liquid interfaces of silicon oxide will be conducted. The effect of the surface on the generation of charged species from exciplexes will also be determined by diffuse reflectance transient absorption spectroscopy. The results of these investigations will lead to a better understanding of the reactions of cationic species at surfaces and the factors governing efficient quenching processes. %%% This grant from the Organic Dynamics Program supports the continuing work of Professor J. Kerry Thomas at the University of Notre Dame. The studies will be directed toward understanding the effect of surfaces on the reactivity of chemical substances and will provide critical data which will allow the development of more efficient chemical systems. The investigation will utilize equipment capable of detecting events on the order of less than a billionth of a second. Thus it will be possible to measure the rapid hopping of charged species in a variety of media. The use of target molecules which undergo rapid fluorescence decay processes provides a means of monitoring chemical processes on a time scale which would otherwise be inaccessible.