Construction and mechanism of phase-locked structured PU elastomers with tunable mechanical and self-healing properties

Self-healing elastomers with great mechanical properties have attracted much attention, however how to balance the mechanical property and self-healing performance is still challenging. In this work, we prepared polyurethane elastomers (PU-n) with different phase-locked structures in which dynamic disulfide bonds and hydrogen bonds are locked at low temperature to provide great mechanical strength and activated by heating to promote self-healing. PU-n exhibit tensile strength from 0.83 MPa to 11.98 MPa because of different microphase separation structures, which is attributed to different thermodynamic compatibility and hydrogen bonds between hard segment with different lengths and soft segment. PU-n can repair surface scratches within 10 min and the well-designed elastomer (PU-50) can achieve a full-cut self-healing efficiency above 90 % at 60 degrees C for 2 h. The self-healing process is dependent on the dynamic recombination of hydrogen bonds and disulfide bonds, which can be accelerated by heating because of the faster molecular motion. The dynamics characteristics of hydrogen bonds and disulfide bonds also endows PU-n with the recyclability, the recycled elastomer exhibits similar mechanical and self-healing properties with original elastomer. This work provides an effective strategy to achieve self-healing polyurethanes with the high mechanical strength.