Curing characteristics, kinetics, and thermal properties of multifunctional fluorene benzoxazines containing hydroxyl groups

Abstract In this article, 9, 9‐bis (4‐aminophenyl)‐2, 7‐dihydroxy‐fluorene (BADHF) was synthesized using methylsulfonic acid as catalyzer by direct condensation. Two kinds of novel multifunctional benzoxazine monomers containing fluorenyl groups and hydroxyl groups (MB‐FH) were obtained from the chemical reaction of BADHF, salicylaldehyde, paraformaldehyde, and ethanolamine (or diethyleneglycolamine) through the adoption of o‐hydroxy‐benzylamine method and one‐step Mannich condensation reaction method. In the traditional three‐step synthesis method, the double bond reduction process took 8–12 h, but in this article, it only took 15 min. The structures of MB‐FH monomers and their intermediates were characterized by Fourier transform infrared spectroscopy (FTIR), 1 H nuclear magnetic resonance ( 1 H NMR). The curing behaviors, curing kinetics, and thermal properties of MB‐FH monomers were tested by using a dynamic rheometer, differential scanning calorimeter (DSC), FTIR, dynamic mechanical analysis (DMA), and thermogravimetric analyzer (TGA). The curing induction time can be apparently shortened by the introduction of hydroxyl groups into benzoxazine monomers, and it can catalyze the ring‐opening polymerization of oxazine rings at lower temperatures, and improve the interaction of hydrogen bonds in the structure of polybenzoxazine.