Extremely Stretchable, Self-Healable Elastomers with Tunable Mechanical Properties: Synthesis and Applications

Abstract

Stretchable and autonomously self-healable elastomers with wide-ranging tunable mechanical properties have attracted increasing attention in various industries. To date, it continues to be a huge challenge to synthesize self-healing elastomers integrating extreme stretchability, relatively high mechanical modulus, and autonomous and rapid self-healing capability. Herein, we propose a novel covalent/supramolecular hybrid construction strategy, in which the covalent cross-links are responsible for providing high modulus and elasticity, while supramolecular cross-links realize extreme stretchability and rapid self-healing under room temperature depending on the ultrafast exchange kinetics of metal–ligand motifs and multicoordination modes. The representative polyurea hybrid elastomer, CSH-PPG-Zn-0.25, can be stretched more than 180× its original length with the highest Young's modulus (1.78 ± 0.08 MPa) among reported ultrastretchable materials. CSH-PPG-Zn-0.25 can fully restore mechanical properties of completely cut samples within 3 h. Note that the healing process can take place under a low temperature of −20 °C and unaffected by surface aging and atmospheric moisture. Merely tailoring the molar ratio of metal/ligand actualizes wide-ranging tunability of mechanical and dynamic properties, such as Young's modulus (from 1.71 ± 0.08 MPa to 5.56 ± 0.22 MPa), maximum tensile strength (from 0.32 ± 0.03 MPa to 4.42 ± 0.23 MPa), strain at break (from >18000% to 630 ± 27%), and storage modulus, ascribed to the increase of cross-linking density and formation of stiff ionic clusters. On the basis of the different material characteristics, two typical elastomers are employed, respectively, as flexible and self-healable conductor and self-healable automotive paint. Benefiting from the fantastic antiaging and low-temperature healing features of CSH-PPG-Zn-0.25, the prepared Ag-NWs/CSH-PPG-Zn-0.25 conductor can even regain its conductive function below zero. CSH-PPG-Zn-0.50 material, meeting the strict mechanical requirements of automotive paints, is able to thoroughly eliminate the surface scratches and recover anticorrosion function in the local damaged region under the atmospheric environment.