Mannich reaction as an interesting synthetic route for the development of energetic benzoxazine polymers

Abstract

In this study, three new energetic benzoxazine monomers were synthesized via a one-step Mannich reaction process involving the incorporation of explosophore nitro groups (NO2) in different positions (ortho, meta and para) into the monomer backbone. The molecular structures of the synthesized monomers were confirmed by FTIR, 1H and 13CNMR techniques. The curing behavior, thermomechanical properties and the thermal stability were assessed by DSC-TGA analyses. All monomers displayed two exothermic peaks related to the polymerization and degradation steps except 4-NBZ that present the polymerization and the degradation phenomena through one unique exotherm pic. The energetic performances were evaluated by the determination of the heat of combustion using a bomb calorimeter in an oxygen atmosphere. The results indicated that the para position provided the benzoxazine monomers with a high calorific value comparable to that of the nitrocellulose (about 10.401 kJ/g). Meanwhile, the aforementioned monomer was found to ignite at a temperature of about 267 °C. Overall, this study showed that the ease of synthesis of the benzoxazine resins via Mannich reaction can be further extended the energetic field and further researches are undergoing to fully unravel the potential of these exceptional materials.