Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo-oxidative stabilization of the α-cristobalite phase in its amorphous regions

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2012-08, Vol.50 (15), p.3158-3170
• Main Authors: Kolel-Veetil, Manoj K., Fears, Kenan P., Qadri, Syed B., Klug, Christopher A., Keller, Teddy M.
• Format: Article
• Language: English
• Subjects: acetylene; amorphous; Applied sciences; Chemical modifications; cristobalite; crosslinked; crosslinking; Exact sciences and technology; high temperature materials; hydrosilylation; Inorganic and organomineral polymers; inorganic-organic; Karstedt's; nanoparticles; network; Physicochemistry of polymers; polymerization; POSS; silicon oxycarbide; silsesquioxane; thermal; thermal properties; thermogravimetric analysis (TGA)
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.26102

A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state 13C and 29Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 A crosslinked network with POSS cores formed by an unusual hydrosilylation reaction was thermally treated in either argon or air up to 1000 °C. The symmetrically‐functionalized POSSs, in fluorite silica phase, remained unchanged on thermal treatment due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed upon cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air.