Molecular Structure Analysis of Aminophenyl Silsesquioxane (Preprint)
MICHIGAN STATE UNIV EAST LANSING DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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The molecular structures of aminophenyl substituted silsesquioxanes, prepared by two different approaches, have been investigated using 29Si NMR spectroscopy. Aminophenyl silsesquioxane prepared by nitrationreduction of octaphenyl POSSRegistered, exhibits broad resonances in the 29Si NMR spectrum, whereas aminophenyl silsesquioxanes prepared directly from aminophenyltrimethoxysilane exhibit very narrow line widths. Wide-angle X-ray diffraction of the products from the direct synthesis show a diffraction peak with a d-spacing value similar to the 101 hkl reflection peak of the rhombohedral lattice seen in several other crystalline POSSRegistered octamers, whereas the products from the nitrationreduction exhibit no diffraction peaks. Our analysis suggests that aminophenyl silsesquioxane prepared by the nitrationreduction of octaphenyl POSSRegistered no longer retains the Si-O structure of the starting octaphenyl POSSRegistered, while the aminophenyl silsesquioxanes prepared by the direct synthesis have significant Si-O cage structure. Thermogravimetric analysis on both products indicates that the aminophenyl silsesquioxanes from the direct synthesis have better thermal and thermo-oxidative stability TOS. Furthermore, this improved thermal stability is extended to highly crosslinked resins prepared from the phenylethynyl phthalimide derivatives of the aminophenyl silsesquioxanes. The thermal analysis suggests that the discrete Si-O frameworks found in POSSRegistered monomers play an important role in maximizing the thermal and thermal-oxidative stability of the materials in which they are incorporated.
- Physical Chemistry
- Atomic and Molecular Physics and Spectroscopy
- Nuclear Physics and Elementary Particle Physics