Synthesis of nitrile-containing ortho-amide benzoxazines for achieving thermosets with low curing temperature and superior performance†

In this work, a molecular design strategy by incorporating nitrile into ortho-amide benzoxazines was employed for achieving promising high performance thermsosets. We conducted a systematic investigation into the influence of additional nitrile moieties on the properties of ortho-amide benzoxazines. Initially, structural characterization of benzoxazines was performed using NMR and FT-IR spectroscopy, followed by DSC analysis and in situ FT-IR spectroscopy to study the polymerization mechanisms of each benzoxazine monomer. Notably, the thermoset derived from ortho-amide benzoxazine bearing two nitrile groups exhibited exceptional thermal stability (T_d5 of 392.5 °C) and high glass transition temperature (T_g of 331 °C), alongside preferable flame retardancy (THR = 3.9 kJ g⁻¹).This approach resulted in a new series of thermosetting resins with low curing temperature and improved comprehensive properties, thereby offering significant potential for the development of advanced thermoset materials with a wide range of intelligent applications.