Thermally stable polybenzoxazines via ortho-norbornene functional benzoxazine monomers: Unique advantages in monomer synthesis, processing and polymer properties

Abstract

Monofunctional and difunctional benzoxazines with ortho-norbornene functionality have been synthesized via Mannich condensation. The structure of synthesized monomers has been confirmed by 1H nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The ortho-norbornene functional benzoxazine resins show excellent features both in the synthesis of benzoxazine monomers and the properties of the corresponding thermosets. The benzoxazines containing norbornene groups can polymerize with multiple polymerization mechanisms rather than the single mechanism common to traditional 1,3-benzoxazine resins. The polymerization mechanisms are monitored by in situ FT-IR and differential scanning calorimetry (DSC). Activation energy of polymerization is also studied by DSC. Moreover, the thermoset derived from the difunctional benzoxazine monomer exhibits high thermal stability with the glass transition temperature of 365 °C and a high Td5 of 463 °C.