A series of novel high molecular weight benzoxazines, A2+B3-type hyperbranched benzoxazines (HB-BA-ta and HB-BAF-ta), were successfully synthesized for the first time via Mannich condensation by using bisphenol A or bisphenol AF as A2 monomers and triamine as B3 monomer. Their chemical structures were identified by 1H NMR and FT-IR. The molecular weight of the hyperbranched benzoxazines was characterized by GPC. Their thermal polymerization behavior was monitored by DSC and FT-IR. The thermomechanical and thermal properties of the cross-linked hyperbranched polybenzoxazines were measured by dynamic mechanical analysis and thermogravimetric analysis. The curing process of hyperbranched benzoxazines was similar to the typical thermal ring-opening polymerization of 1,3-benzoxazines, but their initial and peak temperatures (144 and 233 oC for HB-BA-ta and 156 and 235 oC for HB-BAF-ta, respectively) were lower than those of benzoxazine monomer due to the abundant OH groups in the end of polymer chains. The cross-linked hyperbranched polybenzoxazines exhibited high glass transition temperature (Tg) and good thermal stability. The Tg values of poly(HB-BA-ta) and poly(HB-BAF-ta) were 206 and 209 oC, respectively. The decomposition temperatures at weight loss 5% and 10% under nitrogen atmosphere were around 340 and 370 oC, respectively. The char yields of poly(HB-BA-ta) and poly(HB-BAF-ta) at 800 oC were 38.8% and 42.4%, respectively. In addition, the hyperbranched benzoxazines showed good solubility in common solvent except for ethanol and toluene.

Novel hyperbranched benzoxazine: Synthesis and properties

255th National Meeting (2018)

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