Hybrid organic-inorganic materials: Synthesis and characterization of organic bridged polysilsesquioxanes

Hybrid organic-inorganic materials are designed to combine the favorable physical properties of organic polymers and inorganic oxides. This dissertation focuses on the synthesis and characterization of hybrid organic-inorganic materials in which the organic and inorganic portions are contained within the same molecular precursors. These organic bridged polysilsesquioxanes are prepared by the sol-gel polymerization of {dollar}alpha,omega{dollar}-bis(triethoxysilyl) substituted monomers.; Chapter 2 focuses upon the application of organic bridged polysilsequioxanes to second order nonlinear optical (NLO) materials. Since the magnitude of the NLO response is directly related to the extent of conjugation between the electron donor and acceptor portion on the NLO active organic chromophore, chromophores with extended conjugation were synthesized. Thus, a more efficient synthesis of 4-nitro-N,N-bis((3-triethoxysilyl)propyl) aniline 10 (82.5% vs. 3.2%) was achieved. Optical quality thin films were synthesized and the NLO properties of these films were probed by Second Harmonic Generation.; Chapter 3 describes the synthesis of materials that combine the characteristics of polyimides and silica. Polymerizations of the bridged bisimide triethoxysilyl monomers occurred rapidly ({dollar}<{dollar}5 min) at ambient temperature in THF under acidic (HCl) conditions to give transparent or translucent xerogels. Thin films were cast at ambient temperatures and later cured under moderate temperatures (100{dollar}spcirc{dollar}C). The thermal stability was measured by Thermal Gravimetric Analysis (TGA) and the hardness was measured by a Vickers Hardness Determination.; Finally, Chapter 4 details the influence of the nature of the bridging organic spacer upon the surface area and porosity of hybrid organic inorganic polysilsesquioxanes. This was accomplished by the synthesis and polymerization of a variety of novel sol-gel processable monomers. Variables in the organic bridging group included changes in the hydrophobicity of the bridging organic spacer, polymerization solvent, along with the effect of inserting a double bond in the hydrocarbon bridge.