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

Abstract

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 1H and 13C NMR, and the purity is calculated by 1H 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 (Tg) 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 Tg, which is against many of such examples available in the literature. Discussions on understanding benzoxazine structure–property relationships have been provided.