Effects of TriSilanolIsobutyl-POSS on thermal stability of methylsilicone resin

Methylsilicone resin/polyhedral oligomeric silsesquioxane (POSS) composites with various proportions of POSS monomer were synthesized by the reaction of functionalized TriSilanolIsobutyl-POSS macromonomer with hydroxyl-terminated methylsilicone resin. The structures of the obtained hybrid polymers were characterized with Fourier-transformed infrared (FT-IR) and transmission electron microscopy (TEM). The FT-IR spectra suggested successful bonding of TriSilanolIsobutyl-POSS and methylsilicone resin. TEM analysis showed that POSS can dissolve in methylsilicone resin at the molecular level. The influences of TriSilanolIsobutyl-POSS on the thermal stability and degradation behavior of methylsilicone resin were studied by thermogravimetric analysis (TGA), solid-state ²⁹Si NMR and X-ray photoelectron spectroscopy (XPS). All these techniques showed that TriSilanolIsobutyl-POSS incorporation results in increased decomposition temperatures and oxidation resistance, primarily by reducing the effect of silanol end groups on the thermolysis through condensation reaction of Si-OH groups and partial loss of isobutyl followed by the formation of an inorganic SiO₂ layer to prevent methylsilicone from further degradation.