Readily self-healing polymers at subzero temperature enabled by dual cooperative crosslink strategy for smart paint

Achieving the artificial supramolecular polymer with excellent low temperature self-healing capability has been a new topic of great significance in soft robotic actuators and smart coating. Nevertheless, the production of robust polymer with decent low temperature self-healing ability is severely impeded by its high crosslink density and low dynamic crosslink bond. Here, we report a design strategy that both low crosslink density and high dynamic crosslink bonds are introduced into polyurea networks to achieve a tough and low-temperature healable supramolecular system of polypropyleneglycol (PPG)-polydimethylsiloxane (PDMS)-Zn (abbreviated as PPG-PDMS-Zn). Incorporating the long PPG segments into linear PDMS chains endows the resulting polymer with relatively low crosslink density, allowing fast polymer chains movement to unite fractured surfaces. Moreover, the dynamic characteristics and self-healing capability of the supramolecular network were effectively enhanced by combining the unique dynamic exchange feature of weak Zn-urethane coordination bonds and low temperature inhibition-dissociation effect of hydrogen bonds. As a result, the representative sample of PPG-PDMS-Zn-0.5 polymer displays a robust tensile strength of 0.98 MPa and a high self-healing efficiency of 97% at -20 degrees C, and these features have rarely been achieved in the previously reported materials. With these promising characters, such kind of supramolecular polymers can find wide applications in fields of anti-icing and winter anti-frosting paints, and antarctic pole exploration as well.