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 H-1 and C-13 NMR, and the purity is calculated by H-1 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.