Segmented epoxy-based non-isocyanate polyurethanes with thermoreversible Diels-Alder junctions

The development of non-isocyanate polyurethanes (NIPUs) has attracted increasing attention as a sustainable alternative to conventional polyurethane chemistry due to the elimination of toxic isocyanates while maintaining the versatility of segmented polymer architectures. In this work, a novel synthetic strategy for the preparation of segmented NIPUs was developed using epoxide chemistry. The soft and hard segment precursors were obtained by epoxidation from polytetramethylene ether glycol (PTMEG, M _n = 2000 g mol^-1), polycaprolactone diol (PCD, M _n = 2000 g mol^-1), and from a hydroxy-urethane derived from furfurylamine, respectively. Polymerization was carried out in two consecutive steps. Initially, the epoxidized soft- and hard-segment precursors were reacted with 1,6-hexamethylenediamine to form furan-terminated prepolymers containing secondary hydroxyl groups. Subsequently, chain extension was achieved through thermoreversible Diels-Alder coupling with bismaleimide, yielding segmented polyurethane networks. Synthesized NIPUs were characterized via FTIR, NMR, and MALDI-TOF MS, and their structure-property relationships were investigated using DSC, DMA, SEM, swelling, and tensile tests. Owing to the incorporation of thermoreversible Diels-Alder linkages, the prepared polymer networks also exhibited intrinsic self-healing capability. The proposed synthetic approach provides a straightforward and environmentally benign route toward segmented non-isocyanate polyurethanes offering broad opportunities for tailoring material performance through molecular design.