Fig. 3: Mechanical properties of DiMPUs.
a Engineering stress-strain curves and b typical true stress-strain curves of PPU and DiMPU-Cu elastomers. Inset in b Photograph showing a DiMPU-Cu1 thin sheet specimen (weight: 0.1 g) lifting a weight of 5.0 kg. c Cyclic tensile test curves of DiMPU-Cu1 in successive loading-unloading cycles with increasing strains, performed without delay time. d The corresponding hysteresis area of PPU, DiMPU-Cu0.5, and DiMPU-Cu1 at each loading-unloading cycle. e Cyclic stress-strain curves for DiMPU-Cu1 under ten consecutive cycles with 300% strain and no waiting time, followed by recovery at 50 °C for 1 h (Cycle 11). f Quantification of the cyclic behavior: hysteresis ratio (left y-axis) and recovery degree (right y-axis) for DiMPU-Cu1. (1–10: continuous; Cycle 11 tested after 1 h recovery at 50 °C). g Photographs of the original, elongated, and recovered DiMPU-Cu1 elastomers. h Comparison between DiMPU-Cu1 and previously reported similar materials in terms of ultimate stress, recovery degree, and toughness improvement factor (the toughness ratio of metal-coordinated versus non-coordinated samples). i Tensile curves of intact and notched DiMPU-Cu1.
