Synthesis of isoliquiritigenin-based bio-benzoxazine and its role of latent curing agent for achieving high-performance epoxy thermosetting systems

Epoxy resins are widely utilized in industrial applications owing to their outstanding thermal mechanical performance and chemical resistance. Nevertheless, conventional epoxy resins often suffer from poor storage stability once blended with curing agents, which limits their broader application. To address this limitation, a novel bio-based benzoxazine monomer ( ISO-fa ) was strategically synthesized through molecular design employing isoliquiritigenin, furfurylamine, and paraformaldehyde as raw materials. The incorporation of intramolecular hydrogen bonding imparts latent curing characteristic to this monomer, enabling precise control over the curing process. Besides, the resulting polybenzoxazine ( poly(ISO-fa) ) demonstrated an exceptional integration of thermal properties. When employed to apply as latent curing agent for the epoxy resin (DGEBA), ISO-fa facilitated the development of an intelligent system that combined latent curing behavior with enhanced material performance. Specifically, DGEBA/ISO-fa exhibited significantly improved storage stability and its resulting poly(DGEBA/ISO-fa) showed exceptional performance with a glass transition temperature ( T g ) of 210 °C, a residual char yield of 39.9 % at 800 °C, and a remarkably low heat release capacity (HRC) of 94.53 J·g⁻¹ ·K⁻¹ . This study addresses the limitations of conventional epoxy resins and provides an innovative strategy for developing high-performance single-component epoxy thermosetting systems. Moreover, the newly obtained ISO-fa also represents a practical example of how molecular design can be leveraged to achieve both processability and performance enhancements in advanced materials.