Synthesis and characterization of novel bio-based benzoxazines from gallic acid with latent catalytic characteristics

Abstract

A novel bio-based main chain benzoxazine with two oxazine rings and one phenolic hydroxyl group in the same aromatic ring was synthesized and characterized. The method includes the synthesis of polymeric benzoxazine precursors from simple chemicals such as gallic acid, gallic amide, 4,7,10-trioxa-1,13-tridecanediamine and formaldehyde by using traditional main chain synthesis methodology. The precursors were successfully characterized by the spectral and thermal investigations using H-1 NMR, FTIR, GPC, DSC and TGA. The results demonstrated that phenolic hydroxyl groups in the benzene ring which are adjacent to the two oxazine rings have a great effect to reduce ROP temperature of benzoxazines. The clear reduction in ROP temperature was demonstrated by tracking exotherm in DSC analysis with an onset value at 126 degrees C. Moreover, thermal stability of the final products were investigated by TGA and high char yields observed.