Thermally healable/heat-resistant properties of thermosets bearing dynamic and thermally stable bonds formed by the Diels-Alder and thiol-maleimide “click” reactions

The thiol-maleimide “click” reaction of 4,4′-bismaleimidodiphenylmethane (BMI) and furfuryl mercaptan generated 4,4′-bis(2-furfurylthiosuccinimido)diphenylmethane (BFSI). Mixtures of BFSI, BMI, and a tetrathiol (S4P) at a (furan+thiol)/maleimide ratio of 1/1 were prepolymerized at 100 or 200 °C and molded at 100-120 or 200-230 °C to produce cured products (BFSI-BMI-S4Ps or hBFSI-BMI-S4Ps). The FT-IR analysis revealed that the thiol-maleimide and DA reactions occurred for BFSI-BMI-S4Ps, while the structure of DA adducts was not retained for hBFSI-BMI-S4Ps. The BFSI-BMI-S4Ps were thermally healable, and the healing efficiency increased with the increase in the S4P/BFSI ratio unexpectedly. Although the hBFSI-BMI-S4Ps were not healed, they exhibited better thermo-mechanical properties than BFSI-BMI-S4Ps.