Synthesis and characterization of self-healing cross-linked non-isocyanate polyurethanes based on Diels-Alder reaction with unsaturated polyester

A green method is established to prepare soft self-healing cross-linked non-isocyanate polyurethanes (SH-NIPUs). Three non-isocyanate polyurethane prepolymers with furan terminal groups (F-NIPUs) were synthesized through a ring-opening reaction of diglycerol bis(cyclic carbonate) with isophoronediamine and furfurylamine under mild reaction conditions. New SH-NIPUs were prepared via a Diels-Alder reaction between F-NIPUs and unsaturated polyester. The obtained SH-NIPUs were characterized by H-1 NMR, ATI-FTIR, DSC, polarized optical microscope, and tensile strength after being damaged and healed. The SH-NIPUs exhibited a Tg between -4 and 20 degrees C, and a relatively low reverse Diels-Alder temperature between 90 and 100 degrees C. Soft SH-NIPUs with high self-healing efficiency up to 100% were achieved successfully.