Synthesis of a smart bisbenzoxazine with combined advantages of bismaleimide and benzoxazine resins and its unexpected formation of very high performance cross-linked polybenzoxazole

We report a bisbenzoxazine thermosetting system, oHPMI-ddm, which shows combined advantages of both bismaleimide and benzoxazine resins. The chemical structure of oHPMI-ddm has been identified by FT-IR and NMR spectroscopies, and its polymerization processes have been investigated using differential scanning calorimetry (DSC) and in situ FT-IR. The resulting polybenzoxazine derived from this thermosetting system exhibits significantly higher thermal stability than thermosets polymerized from the commercialized 4,4?-diaminodiphenylmethane based bisbenzoxazine (PH-ddm) and bismaleimide (DDM-BMI). This newly obtained benzoxazine also shows a unique structural thermal rearrangement in comparison to the cross-linked polybenzoxazole in a similar manner as other reported smart ortho-benzoxazines, although it has no obvious hydrogen bond forming group and cannot form 5- or 6-membered intramolecular interaction. Such conversion from polybenzoxazine to polybenzoxazole has been confirmed by both in situ FT-IR and solid state 13C NMR. Furthermore, the finally obtained cross-linked polybenzoxazole possesses outstanding properties of high thermal stability, excellent flame retardancy and low dielectric constant, indicating great potential for high performance material applications.

Automated summary

A novel bisbenzoxazine thermosetting system, oHPMI-ddm, has been developed and characterized, exhibiting higher thermal stability than commercialized bisbenzoxazine (PH-ddm) and bismaleimide (DDM-BMI) thermosets. The polybenzoxazine derived from this system shows unique structural thermal rearrangement and outstanding properties such as high thermal stability, flame retardancy, and low dielectric constant, demonstrating great potential for high performance material applications.