Creep Behavior of an Oxide/Oxide Composite with Monazite Coating at Elevated Temperaturesby Sean S. Musil
This doctoral thesis is mainly focused on synthesis and characterization of some specifically designed monomers and their corresponding conjugated oligomers and polymers via non-traditional [acyclic diene metathesis (ADMET)] or traditional [polyimines] polycondensation techniques. Initially a ruthenium-based catalyst was used to syntheses poly ( p-phenylene vinylene) (PPV) type oligomers applying ADMET. Mainly pure all trans dimeric or trimeric oligomers were recovered, as indicated by NMR. We proved that in this way one could easily access these highly pure oligomers, which might further be used a building blocks for some other reactions. We also synthesized a series of different substituted dialkyl distyryl heteroatom containing (siloxane, silane, germane, stannane) monomers and effectively polymerized by means of ADMET using ruthenium-based catalysts. ADMET yields were up to 95% with all trans configuration. The microstructures of the products were analyzed by means of 1H-NMR, 13 C-NMR, 29Si-NMR, 119Sn-NMR and ATR-FTIR. All methods indicated that the siloxane condensates were exclusively a cyclic dimer where as silane, germane, stannane yielded high molecular weight polycondensates. The optical properties of these materials showed a red shift both in absorption and emission spectra, (∼50nm) relative to the monomer and showed a blue emission. The absorption and emission maxima of these condensates are also higher (∼25 nm) than the t-stilbene unit (main conjugated block between two heteroatoms) indicating the effective participation of heteroatoms (Si, Ge, Sn) in conjugation. In order to incorporate heteroatoms with in a fully conjugated system, we developed a new class of polyazines. In this work we disclose an efficient polycondensation reaction between alpha-omega-diformyl functional aromatics, namely 2,5-diheptyloxy-1,4-diformylbenzene and side-chain substituted alpha-omega-diformyl oligo(p-phenylene vinylene) (OPV) with hydrazine afforded novel soluble and processable conjugated polymers. The reaction conditions were investigated and structural analysis of the polymers was carried out by means of 1H, 13C, 15N NMR, indicating all trans configured C=N-N=C linkages. The optical properties showed a red shift in absorption maxima, (∼31-60 nm) relative to the monomer aromatics due to conjugation through the azine linkage and showed an orange-red emission. The emission maxima also followed the same trend. Thin films of OPV-hydrazine condensate readily undergo n doping.
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