An Apigenin-Based Bio-Benzoxazine with Three Polymerizable Functionalities: Sustainable Synthesis, Thermal Latent Polymerization, and Excellent Thermal Properties of Its Thermosets

Benzoxazine resins have been constantly attracting attention from both academia and industry attributing to their molecular design flexibility and high performance of its thermoset polymer properties. However, a reduction in the polymerization temperature, a renewable resource and improved thermal and mechanical properties are highly desirable in order to meet the requirements of various applications. Herein, we have synthesized a new bio-based benzoxazine resin showing thermal latent polymerization characteristic from renewable apigenin and furfurylamine. This benzoxazine resin possesses the advantage of the long shelf life as other traditional benzoxazines through its intramolecular hydrogen bonding between the phenolic –OH and the carbonyl. In addition, it can be polymerized via multiple polymerization behaviors rather than the single polymerization mechanism as other reported traditional benzoxazines. Moreover, the resulting fully polymerized thermoset derived from this bio-based benzoxazine exhibits a high glass transition temperature of 376 oC, a very high char yield of 66%, and an extraordinarily low heat release capacity of 20.2 J/(g K). The excellent thermal performance and flame resistance evidences its great potential applications in the fields where high-performance materials are needed.