A self-healing polyurethane elastomer with excellent mechanical properties based on phase-locked dynamic imine bonds

Abstract

Self-healing materials with high mechanical strength have attracted much attention, but the facile fabrication of such high-performance materials remains a challenge. In this work, we report a robust self-healing polyurethane elastomer by employing the imine bond, which readily undergoes a dynamic exchange reaction under mild conditions. A symmetric imine-diol chain extender was fabricated through a Schiff base condensation reaction. By tuning the hard segment content, the tensile strength reached up to 40 MPa with elongation at the break of 880%. And in the meantime, it showed an efficient self-healing capability at elevated temperatures, and its mechanical properties were fully recovered (η_σ = 96%) after 2 h of healing at 80 °C. The extraordinary balance between the mechanical properties and the self-healing efficiency was due to two reasons. First, the rigid CN double bond and the symmetric structure of the imine-diol promote microphase separation and facilitate the orientation of chain segments during the strained induced crystallization. Secondly, the dynamic imine exchange reaction is phase-locked in the hard phases. As the temperature is elevated, the self-healing processes are sped up by the accelerated relaxation of hard phases due to the exchange reactions of imine bonds embedded within.