Heat-resistant and robust biobased benzoxazine resins developed with a green synthesis strategy

Using eco-friendly methods to prepare high-performance thermosetting resins is of great significance for cutting-edge industrial fields and sustainable development. In this article, using isoeugenol and vanillin as the phenol source, 3-aminophenyl acetylene as the amine source, the propylene-terminated benzoxazine monomer IE-apa and aldehyde-terminated benzoxazine monomer V-apa were synthesized with a green strategy in the whole synthesis and purification processes. After curing the two monomers, two biobased benzoxazine resins poly(IE-apa) and poly(V-apa) were obtained, and their comprehensive properties were investigated. The results show that poly(IE-apa) and poly(V-apa) have not only high glass transition temperatures (293 °C and 304 °C), but also high storage moduli (3.89 GPa and 3.65 GPa), initial thermal decomposition temperatures (395 °C and 393 °C) and tensile strengths (66.7 ± 2.2 MPa and 59.0 ± 3.2 MPa), and both resins exhibit the best overall performance among all biobased benzoxazine resins from mono-phenols. The high performance of the resins is attributed to the specific structure of the benzoxazine resins, that is, the synergistic interaction between alkynyl and propylene or aldehyde groups.