Thermally Reversible Crosslinked Polyurethanes Based on Blocking and Deblocking Reaction

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%.