Synthesis and characterization of benzoxazine resin-SiO2 hybrids by sol-gel process: The role of benzoxazine-functional silane coupling agent

Sol-gel process has been used to incorporate silica nanoparticles into polybenzoxazine matrix to form polybenzoxazine-silica hybrids. The hybrids have been synthesized by the reaction of bisphenol A/aniline type benzoxazine monomer (BA-a) and tetraethoxysilane as precursor for silica nanoparticles. Triethoxysilane-functional benzoxazine monomer was also prepared from γ-aminopropyltriethoxysilane, phenol and paraformaldehyde, and has been used as silane coupling agent to improve the adhesion between polybenzoxazine matrix as organic domain and silica nanoparticles as inorganic domain. Differential scanning calorimetry (DSC) and FT-IR are used to study the polymerization behavior of benzoxazine monomer in the presence of silica nanoparticles over different temperature range. Dynamic mechanical analysis indicates that the coupling agent is very effective to increase the Tg and the storage modulus of the hybrids. Thermogravimetric analysis also shows the thermal stability of neat polybenzoxazine matrix is improved by the inclusion of silica nanoparticles.