Healable and Recyclable Polyurethane with Natural-Rubber-like Resilience via π-Type Tweezer Structure Stabilizing Dynamical Hard Domains

Abstract

Achieving ultrafast resilience comparable to that of irreversible cross-linking elastomers remains a formidable challenge for self-healing supramolecular elastomers. Herein, we construct a π-type tweezer structure formed by imidazolidinylurea and aromatic imine to stabilize dynamical hard domains (SDHDs) in polyurethane (PU) elastomers. SDHDs endow the dynamic PU network with high binding energy and minimal stress relaxation at room temperature, similar to irreversible covalent cross-links. As such, the elastomer demonstrates rapid resilience comparable to vulcanized natural rubber as well as high mechanical strength and toughness. Meanwhile, SDHDs can be readily activated upon heating, enabling exceptional healing ability (∼100% healing efficiency) under mild conditions (50 °C) and complete recovery of mechanical properties after recycling. More interestingly, the PU elastomer exhibits significant elastocaloric effects with an adiabatic temperature change of −13.5 °C, surpassing that of state-of-the-art vulcanized natural rubber (−9.4 °C). Therefore, this work presents a new approach for structural design that enables a balance between conflicting characteristics and expands the potential applications of self-healing supramolecular elastomers.

Self-Healing and Degradable Polycaprolactone-Based Polyurethane Elastomer for Flexible Stretchable Strain Sensors

“…Currently, many self-healable strain sensors based on reversible noncovalent bonds (hydrogen 20−23 and metal coordination bonds 24,25 ) and reversible covalent bonds (Diels−Alder, 26−28 disulfide, 29−31 and imine bonds 32,33 ) have been reported, which significantly improved the durability and prolonged the service life of the sensor. For example, Yan et al prepared a heat-and light-responsive supramolecular elastomer consisting of poly(ethylene glycol), polycaprolactone diol (PCL), and 2ureido-4-pyrimidone.…”

“…An optimal strategy for resolving the aforementioned issue is to endow flexible sensors with self-healing properties. Currently, many self-healable strain sensors based on reversible noncovalent bonds (hydrogen − and metal coordination bonds , ) and reversible covalent bonds (Diels–Alder, − disulfide, − and imine bonds , ) have been reported, which significantly improved the durability and prolonged the service life of the sensor. For example, Yan et al.…”