Syntheses, thermal properties, and phase morphologies of novel benzoxazines functionalized with polyhedral oligomeric silsesquioxane (POSS) nanocomposites

We have successfully synthesized a novel benzoxazine ring-containing polyhedral oligomeric silsesquioxane (BZ-POSS) monomer by two routes: (1) hydrosilylation of a vinyl-terminated benzoxazine using the hydro-silane functional group of a polyhedral oligomeric silsesquioxane (H-POSS) and (2) reaction of a primary amine-containng POSS (Amine-POSS) with phenol and formaldehyde. The benzoxazine-containing POSS (BZ-POSS) monomer can be copolymerized with other benzoxazine monomers through ring-opening polymerization under conditions similar to that used for polymerizing pure benzoxazines. Thermal properties of these POSS-containing organic/inorganic polybenzoxazine nanocomposites have been improved over the pure polybenzoxazine analyzed by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The BZ-POSS monomer is poorly miscible with the benzoxazine monomer and tends to aggregate and forms its own domains, both before and after polymerization. At a higher BZ-POSS content, gross aggregation occurs and results in a lower than expected improvement in the thermal properties.