Synthesis, polymerization, and thermal properties of benzoxazine based on p-aminobenzonitrile

The 6,6′-bis(3-benzonitrile-3,4-dihydro-2H-benzo[e][1,3]oxazinyl) isopropane (BA-PABN) was synthesized from bisphenol-A, p-aminobenzonitrile and paraformaldehyde via solventless method. The chemical structure of BA-PABN was confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis, and the polymerization of BA-PABN was investigated by FTIR, solid-state 13C NMR, and differential scanning calorimetry. BA-PABN undergoes the oxazine ring-opening polymerization and the cyclotrimerization of cyano groups with the formation of the corresponding polybenzoxazine (PBA-PABN). Dynamic mechanical analysis results show the storage modulus of PBA-PABN at 25 °C is about 2.7 GPa, and the glass transition temperature is 190 °C. The 5% and 10% weight loss temperatures of PBA-PABN are 300 and 325 °C in both air and nitrogen, respectively. The char yield is about 43% at 800 °C in nitrogen, whereas almost no degradation residue is remained at 750 °C in air.