A transparent, highly stretchable, self-healing polyurethane based on disulfide bonds

Polymers with self-healing ability have attracted great research efforts recently. A transparent self-healing polyurethane (PU) based on disulfide bonds is reported in this work. The crystalline structures, self-healing properties of the polyurethane were investigated by differential scanning calorimetry (DSC), X-ray diffraction measurements (XRD), dynamic mechanical analysis (DMA), stress relaxation and tensile tests. The as-prepared self-healing polyurethane was transparent due to low crystallinity and exhibited excellent self-healing properties, stretchability and healing repeatability. The healing efficiency and elongation at break at a moderate healing temperature were over 90% and 800%, respectively. Meanwhile, the self-healing polyurethane exhibited an excellent healing repeatability and service reliablility. The self-healing mechanism was analyzed through surface analysis of the scratches and shape memory effect. The system was composed of a polyurethane network, which was responsible for the autonomous crack closure due to its shape memory characteristic, and an intrinsic self-healing component through dynamic disulfide bond exchange. The self-healing polyurethane might have potential applications in the fields of flexible electronics, including artificial skins, soft robotics, etc.