Synthesis of linear polyurethane bearing pendant furan and cross-linked healable polyurethane containing Diels–Alder bonds

Primary mono-amine (furfuryl amine) is functionalized as a chain extender to obtain linear polyurethane bearing pendant furan groups (L-PU-Furan), unlike the previous research (furanic diols as chain extender). Furfuryl amine can functionalize as a chain extender due to the reactivity between the resultant urea group and NCO group at higher temperatures. Pendant cross-linked polyurethane containing a DA bond (C-PU-DA) is obtained from the cross-linking of L-PU-Furan and a bismaleimide (BMI) via a Diels–Alder reaction. L-PU-Furan and C-PU-DA are characterized by 1H NMR, FTIR, DSC and TGA. The results of 1H NMR and gel–solution–gel experiments demonstrate that the C-PU-DA exhibits excellent thermal reversibility. C-PU-DA exhibits good healable properties as evidenced by the evolution of a crack versus temperature observed under polarizing optical microscopy. C-PU-DA exhibits good mechanical properties and healing efficiency, determined by breaking (tensile) strength measurements.