Well-defined organic–inorganic hybrid benzoxazine monomers based on cyclotriphosphazene: Synthesis, properties of the monomers and polybenzoxazines

Well-defined organic–inorganic hybrid benzoxazine monomers based on cyclotriphosphazene (CP) cores have been synthesized. Theses monomers possessed controllable number of organic benzoxazine moieties and biphenyl groups distributed on the inorganic ring of CP. Corresponding ring-opening polymerization under heat led to highly cross-linked polymers with different number of crosslinking sites. The ring-opening polymerization behaviors of the new benzoxazine monomers were investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA). The results indicated that the polymerization activity of the monomers depended on the number of benzoxazine moiety of corresponding monomers. Those monomers with more benzoxazine moieties resulted in higher polymerization rate. Due to the high crosslinking nature with rigid and stable inorganic CP ring and biphenyl groups in the networks, the resulted polybenzoxazines from the monomers showed excellent thermal stability, mechanic property and humidity resistance.