Constructing Sacrificial Multiple Networks to Toughen Elastomer

Designing sacrificial bonds or networks has emerged as a popular strategy to fabricate high-performance elastomeric materials. Herein, we consider the properties of a special kind of double sacrificial multiple networks (MNs), which are composed of one chemically cross-linked covalent network, one noncovalent hydrogen bond network, and one noncovalent coordination network. We examine the effects of the chemical cross-linking density C, the number of coordination beads N_c, and the coordination interaction strength ϵ_c on the structural characteristics of these MNs. The larger concentration of coordination beads and stronger coordination interactions are shown to result in a larger coordination network which partly replaces the hydrogen bond network. By applying triaxial deformation, we evaluate the toughening mechanism of the MNs and determine the key parameters underlying the toughness of the MNs. In systems with strong coordination interactions, the enhanced toughness is shown to arise from the long and oriented polymer fibers induced by physical cross-linking sites in the coordination network. Furthermore, the characteristic sequential breakage of the different sacrificial networks occurs during deformation, with the hydrogen bond network sacrificed to dissipate energy during the initiation of strain, followed by the coordination network at much larger magnitudes of tensile strain. In general, this simulation study not only demonstrates the toughening mechanism of the double sacrificial networks in MNs under deformation but also provides some guidelines for the fabrication of materials with good mechanical properties via multiple network design.