Improving the Thermal Stability of Polybenzoxazines Through Incorporation of Eugenol-Based Benzoxazine

To introduce the para-position of phenol or aniline moiety into the cross-linked network of polybenzoxazine and improve its thermal stability, benzoxazine based on eugenol and 4,4’-diaminodiphenylmethane (e-ddm) was copolymerized with bisphenol A-aniline-based benzoxazine (b-a) or phenol-aniline-based benzoxazine (p-a). The differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR) results show that the carbenium ion intermediate from e-ddm could react with the para-position of phenol or aniline in b-a and p-a during the ring-opening polymerization process, resulting in that the aniline and phenol moieties were introduced into cross-linked structures of polybenzoxazines. The thermogravimetric analysis (TGA) and TGA interfaced with FTIR results indicate that the thermal stability of polybenzoxazines increased with the incorporation of e-ddm, due to that the volatilization of phenol, aniline and their derivatives was restrained during the thermal degradation processes. Thereby, introducing e-ddm into benzoxazine is a better method of increasing the thermal stability of polybenzoxazine.