Synthesis, thermal properties and curing kinetics of fluorene diamine-based benzoxazine containing ester groups

A novel diamine-based benzoxazine monomer containing ester and bulky fluorene groups (BABPF-p) was successfully synthesized by the reaction of 9,9-bis-[4-(4-aminobenzoyloxy)phenyl]fluorene with paraformaldehyde and phenol. The chemical structure of monomer was confirmed by Fourier-transform infrared (FTIR) and 1H and 13C nuclear magnetic resonance spectroscopy (1H and 13C NMR). The polymerization behavior of monomer was analyzed by FTIR. The curing kinetics was studied by differential scanning calorimetry (DSC), and the kinetic parameters were determined. The autocatalytic model and Kamal model showed good agreement with the experimental results. The thermal and mechanical properties of poly(BABPF-p) were evaluated with DSC, dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA). The cured polymer exhibited the higher glass transition temperature (Tg) than diaminodiphenylmethane-based benzoxazine (P-ddm) and fluorene diamine-phenol-based polybenzoxazine (poly(BF-p)). The incorporation of flexible ester carbonyl linkages into the macromolecular backbone had slight effect on the thermal stability of fluorene-containing polybenzoxazine.