In spinal degenerative disease, an injectable liquid hydrogel can fill in defect entirely, lessen the danger of implant relocation and following loss of disc height, minimizing the operative trauma. Here, we propose an injectable in-situ chemically cross-linked hydrogel by a two-component reaction of liquid silk fibroin with liquid polyurethane at physiological temperature conditions. Confined compression tests and fatigue tests were reported to assess physical properties of the hydrogel. Impact of different diameter on the biomechanical behaviours was tested to evaluate the clinical potentiality of the hydrogel for replacing nucleus pulposus. Degradation behaviours in different solutions and animal experiments were also investigated to examine the tissue biocompatibility of the hydrogel. The hydrogel modulus was affected by the hydrogel geometrical (diameter) parameters. SF/PU composite hydrogel can survive a million cycles, unconstrained fatigue resistance. More importantly, in vivo biocompatibility using New Zealand white rabbits, showed good biocompatibility over a three-month period in culture. Particularly, they showed the significant clinical merit of providing stronger axial compressive stiffness on confined compression test. Based on the outcomes of the present research, the SF/PU composite hydrogel may provide significant advantages for use in future clinical application in replacing nucleus pulposus field.

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New self‐healing crosslinked bisphenol‐S polyurethane (BPS/PU) including thermal reversible urethane bonds is prepared to balance the mechanical and self‐healing properties. BPS/PU is synthesized with BPS as chain extender to improve the mechanical property in the effect of high molecular regularity of BPS and extra stronger physical crosslinking in BPS/PU. The crosslinked structure of BPS/PU is confirmed by Fourier transform infrared spectra and swelling‐dissolution test. BPS/PU demonstrates great thermal reversability after three heating and cooling cycles and exhibits shorter relaxation time (3.3 min). The tensile strength and the tensile elongation of BPS/PU are up to 14.54 MPa and 877.12%, respectively, which are much higher than the value reported in literature. The qualitative self‐healing analysis of BPS/PU confirms that the cracks can be healed largely after healing progress, and the quantitative self‐healing analysis exhibits great healing properties with the healing efficiency of up to 77.92%.

The development of self-healing polymers can extend the service life of polymer materials. However, it is still a challenge to prepare a polyurethane with high healing efficiency and maximum retention of the properties of polyurethane itself. In this research, we proposed a new scheme for the industrial production of self-healing polyurethane and successfully synthesized a self-healing polyurethane using diacetyl oxime as the chain extender and triethanolamine as the cross-linking agent. Oximeblocked isocyanates deblock at a higher temperature and regenerate oxime urethanes at a lower temperature, thereby achieving thermal reversibility and self-healing due to the concise and efficient thermal reversible reaction of oxime urethanes. Fourier transform infrared and differential scanning calorimetry experiments confirmed that the oxime urethanes in the polyurethane deblock efficiently at around 90 °C and re-block after the temperature is lowered. The process can be cycled at least three times. Microscopic observation confirmed that the cracks disappeared within 60−90 min at 90 °C. The tensile test shows that the synthetic DiO-c-PU has a self-healing efficiency of over 94% at 90 °C for 1.5 h, which is more efficient. From the results, it appears that DiO-c-PU has good self-healing properties.

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