Preparation And Application Of The Room Temperature Intrinsic Self-healing Polyurea Elastomers

Stretchable and autonomously self-healable elastomers with wide-range tunable mechanical properties have attracted increasing attentions in various industries.Up to now,it is still a huge challenge to synthesize intrinsic self-healing elastomers integrating extreme stretchability,relatively high mechanical modulus,autonomous and rapid self-healing capability.Here,we propose a novel covalent bond/hypermolecular bond hybrid network construction strategy to solve the above problems,in which the covalent crosslinks are responsible for providing high modulus and elasticity;while supramolecular crosslinks realize extreme stretchability and rapid self-healing under room temperature depending on the ultrafast exchange kinetics of metal-ligand motifs and multi-coordination modes.Taking CSH-PPG-Zn-0.25 polyurea hybrid elastomer(n(Zn²⁺):n?imidazole?=1:4)as an example,CSH-PPG-Zn-0.25can be stretched more than 180×its original length with the highest Young's modulus?1.78±0.08 MPa?among reported ultrastretchable materials.In addition,CSH-PPG-Zn-0.25 has excellent self-healing properties,and the cut-repaired polymer spline at room temperature can completely restore its original mechanical properties within 3 h.Note that the healing process is able to take place under a low temperature of-20?and unaffected by surface ageing and atmospheric moisture.By controlling the molar ratio of Zn²⁺/imidazole ligand?0.25,0.33,0.50,1.00?,the crosslink density of the polymer network and the ionic cluster structure inside the polymer can be adjusted to prepare an elastomer with a wide range of mechanical 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.Two typical elastomers?CSH-PPG-Zn-0.25 and CSH-PPG-Zn-0.50?were selected for the preparation of flexible self-repairing conductors and self-healing automotive coatings.Benefiting from the fantastic anti-ageing 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.In addition,CSH-PPG-Zn-0.50 has excellent mechanical properties and room temperature self-healing properties to meet the mechanical properties of automotive coatings;the cracked CSH-PPG-Zn-0.50 automotive coating can completely repair surface cracks and recover anticorrosion function in the atmosphere.