Anomalous Isomeric Effect on the Properties of Bisphenol F-based Benzoxazines: Toward the Molecular Design for Higher Performance

A series of 2,2′-, 2,4′-, and 4,4′-substituted benzoxazine monomers based on isomeric bisphenol F and aniline has been synthesized in order to obtain a basic set of design rules toward making higher performance polybenzoxazines. All the monomer structures are confirmed by 1 H and 13 C NMR, and the purity is calculated by 1 H NMR. The polymerization behavior is studied by differential scanning calorimetry (DSC) and in situ Fourier transform infrared spectroscopy (FT-IR), The rate of polymerization increases in the order 4,4′-, 2,4′-, and 2,2′-substituted monomer. After polymerization, the thermal stability and glass transition temperature ( T g ) of each polymer are studied by thermogravimetric analysis (TGA) and temperature-modulated DSC. The polymer obtained from 2,2′-substituted monomer gives highest thermal stability as well as T g, which is against many of such examples available in the literature. Discussions on understanding benzoxazine structure–property relationships have been provided.