Synthesis of novel multi-functional fluorene-based benzoxazine resins: Polymerization behaviour, curing kinetics, and thermal properties

In this paper, a new series of novel aromatic multi-functional fluorene-based benzoxazine monomers (AMFB) were synthesized from the reaction of 9,9-bis(4-aminophenyl)-2,7-dihydroxy-fluorene, aniline, paraformaldehyde, and unsubstituted or substituted phenol including phenol, p-(tert-octyl)phenol, and nonylphenol, by two-stage Mannich condensation reactions. The structures of intermediates and the final benzoxazine monomers were identified via Fourier transform infrared (FTIR) and Hydrogen and Carbon nuclear magnetic resonance ((HNMR)-H-1 and (CNMR)-C-13) analyses. The rheology, polymerization behaviour, curing kinetics, and thermal stability of the obtained novel benzoxazines thermosets were measured by using rheometer, differential scanning Calorimetry (DSC), FTIR, and thermogravimetric analysis (TGA), respectively. The o-nonyl phenol containing fluorene-based benzoxazine monomer (t-BF-a-n) showed the best processability with the lowest curing energy values. Moreover, the prepared polybenzoxazine thermosets showed excellent thermal stabilities and with higher glass transition temperature (258-333 degrees C) than the traditional difunctional fluorene-based benzoxazine resins.