Ultrasound mediated synthesis of catalytic and polymeric materials

Sonochemical preparation of nanophasic materials arises from acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid irradiated with high-intensity ultrasound. These high energy conditions are utilized for the synthesis of nanostructured materials when volatile precursors are irradiated with high intensity ultrasound. In addition, ultrasonic emulsification of strong reductants mediate the polymerization of a class of polymers. The first part of the thesis describes the synthesis, characterization, and catalytic applications of a nanostructured bifunctional aromatization catalyst. The second part of the thesis involves the design, polymerization, and conversion of carbon-based network polymeric precursors to diamond-like films.; Nanostructured molybdenum carbide supported on HZSM-5. Sonochemical decomposition of molybdenum hexacarbonyl in a hexadecane solution in the presence of HZSM-5 generates a Mo₂C/ZSM-5 bifunctional catalyst. This material consists of a HZSM-5 support with 2–3 nm Mo₂C particles homogeneously dispersed only on the surface of the zeolite, making it an “eggshell” catalyst. Characterization of the catalyst was done by electron microscopy, X-ray photoelectron spectroscopy, and CO chemisorption to characterize the dispersion of Mo₂C particles. The catalyst is both active and selective for the dehydro-aromatization of methane to benzene.; Polymer to diamond-like carbon. Synthesis of a carbon-based network polymer with an sp3 hybridized backbone which upon pyrolysis should yield a diamond-like carbon film. The rational design of an appropriate organic monomer and its polymerization to a network polymer whose weakest bond is between the sp3 hybridized backbone and the capping unit. Molecular weight was determined by GPC and laser light scattering experiments in addition to characterization of the polymer structure was carried out by solution and solid state NMR and is consistent with a quaternary backbone carbon bonded to a benzyl group. The decomposition profile for this polymer was established by TGA-MS. Pyrolysis shows the benzyl unit is the major bond to break in the polymer. Stabilization of the carbon backbone is under hot filament chemical vapor deposition conditions where atomic hydrogen stabilizes the growing diamond film.