[SY-H5] Modulating Elastomer Strength and Toughness with Metal Ligand Cross-linking
Non-covalent cross-linking interactions such as metal ligands can be used to tailor stiffness and structure of linear polymers while enabling interesting features like self-healing, energy dissipation, and extended stretching capability. Here we present a novel system of copper(II) carboxylate bonds used to crosslink a low Tg acrylic backbone. These crosslinks behave in a covalent manner to form novel materials with increased stiffness, strength, and dissolution resistance, and decreased ductility. It was found that substitution of the copper cation with different ligands imparts a dynamic nature to the crosslinks, thereby enabling dissolution and regeneration of the initial linear polymer. These ligands also strongly influence behavior in the solid-state polymer, increasing ductility with minimal stiffness and strength reduction, and enabling self-healing behavior. The polymer was characterized under monotonic uniaxial tensile loading at different temperatures and strain rates. This experimentally observed mechanical behavior is then considered in the context of topological and mechanochemical elastomer models. The mechanochemical model highlights how modulation of the dynamic cross-link strength within an otherwise linear elastomer can modulate bulk mechanical behavior.