In this work, 3-amino phenyl boronic acid (AB) was used as an aniline derivative in the preparation of polybenzoxazine based on phenol. In order to investigate the effect of boronic acid on thermal characteristics, polybenzoxazines based on pure aniline and 50% aniline and AB mixture were also prepared and analyzed. Significant improvements in thermal characteristics, increase in thermal stability and char yield, was recorded for the polymers based on AB or its mixture. This behavior was associated with crosslinked structures generated by condensation reactions of B Symbol of the Klingon Empire OH groups. Morphologic and thermal characteristics of polybenzoxazines samples were investigated by NMR, FTIR, DSC, TGA, and direct pyrolysis mass spectrometry (DP-MS) techniques. Application of DP-MS technique also supplied additional information on crosslinked structures produced by boronic acid units. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019