Mechanically Robust and Self-Healing Elastomers Based on Dynamic Oxime–Carbamate Bonds: A Combined Experiment and All-Atom Simulation Study

Abstract

Elastomers inevitably suffer scratches and damage during the application; thus, the design and fabrication of self-healing elastomers with covalent adaptive networks is a meaningful strategy to extend the service life of materials. In this study, a facile two-step approach was proposed to synthesize self-healing elastomers based on the dynamic oxime–carbamate bonds. Hydroxyl-terminated polybutadiene was first reacted with isophorone diisocyanate to synthesize the prepolymer with isocyanate groups terminated, followed by further reaction with dimethylglyoxime as a chain extender to obtain self-healing elastomers. Specially, all-atom molecular dynamics simulations were used to construct the same model as the experiments. Together with the experimental characterization of FTIR and 1H NMR, all-atom molecular dynamics simulations can further verify the formation of hydrogen bonds and dynamic oxime–carbamate bonds. By fixing the ratio of hydroxyl to isocyanate constant, we found that the mechanical strength increased with the increase of hard segment content. At the same time, the loss factor decreased in the glass transition region and at room temperature. Finally, the self-healing behavior of the elastomer was verified at a certain temperature. The corresponding mechanism is explained by means of molecular dynamics simulations, where dynamic oxime–carbamate bonds play more important roles than hydrogen bonds. The combined simulation and experimental studies provided a reasonable approach for the subsequent self-healing system.