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.

Understanding the application of covalent adaptable networks in self-repair materials based on molecular simulation

“…Triaxial stretching along the z-axis is often used to characterize the repair effect under non-equilibrium molecular dynamics (NEMD) simulation, [51][52][53] where the tensile stress is expressed by P zz . Because bond breakage is not allowed in FENE potential, the quartic potential is adopted to obtain the stressstrain curves:…”

“…Triaxial stretching along the z -axis is often used to characterize the repair effect under non-equilibrium molecular dynamics (NEMD) simulation, 51–53 where the tensile stress is expressed by P zz . Because bond breakage is not allowed in FENE potential, the quartic potential is adopted to obtain the stress–strain curves: U Q ( r ) = K ( r − R c ) 2 ( r − R c )( r − R c − B ) + U 0 where K = 2351 ε / k B , B = −0.7425 σ LJ , R c = 1.5 σ LJ and U 0 = 92.74467 ε LJ .…”

Impact of Sacrificial Hydrogen Bonds on the Structure and Properties of Rubber Materials: Insights from All-Atom Molecular Dynamics Simulations

“…Stress–strain ( σ T – ε T ) curves are generated by uniaxial stretching deformation to determine the mechanical properties, and this method is consistent with our previous study. − To maintain a constant volume within the simulation box, we apply stretching along the Z -direction at a steady engineering strain rate, ε̇ T (as defined in eq ), concurrently reducing the lengths in the X and Y directions at the same rate. where L Z ( t ) and L Z (0) denote the length of the box in the Z -direction at time t and the initial moment, respectively. ε T is the applied tensile strain, and the ε̇ T is set to 10 –8 s –1 . The tensile stress is identified utilizing the bias tensor of the pressure shown below where ∑ i P ii /3 represents the isostatic pressure of the system, and μ represents the Poisson’s ratio of the material, which is set to 0.5.…”

Photoluminescent Self-Healable Waterborne Polyurethane/Mo and S Codoped Graphitic Carbon Nitride Nanocomposite with Bioimaging and Encryption Capability

“…These bonds should have the capability to undergo easy breakage and reformation, facilitating the recovery of the material’s network structure. Ionic interactions, Diels–Alder reactions, oxime bonds, diselenide bonds, B–O bonds, disulfide bonds, and Schiff bases, which are dynamic covalent bonds, have been commonly employed in formulating healable and recyclable SHWPU. Again, certain research studies have suggested that incorporating hydrogen bonds can enhance the mechanical strength of self-healing polyurethane elastomers .…”