A Tough Metal‐Coordinated Elastomer: A Fatigue‐Resistant, Notch‐Insensitive Material with an Excellent Self‐Healing Capacity

Abstract

Self-healing materials can prolong device life, but their relatively weak mechanical strength limits their applications. Introducing tunable metal-ligand interactions into self-healing systems can improve their mechanical strength. However, applying this concept to solid elastomers is a challenge. To address this need, polyurethane-containing metal complexes were fabricated by introduction of a pyridine-containing ligand into polyurethane, and subsequent coordination with Fe 2 + . The strong reversible coordination bond provides mechanical strength and self-healing ability. By optimizing the monomer ratio and Fe 2 + content, the resulting complex possesses a very high tensile strength of 4.6 MPa at strain of around 498 % and a high Young's modulus (3.2 MPa). Importantly, the metal complex exhibits an extremely high self-healing efficiency of approximately 96 % of tensile strength at room temperature and around 30 % at 5°C. The complex is notch-insensitive and the fracture energy is 76186 J/m 2 , which is among the highest reported values for self-healing systems. specimens were stretched until the notch turned into a running crack to determine the critical length (Lc). Fracture energy was determined as Γ = W Lc ð Þ a0 b0 , where Γ represents the fracture energy, a 0 represents the sample width, b 0 represents the sample thickness. 4 5 6 7 8

Rugged Soft Robots using Tough, Stretchable, and Self‐Healable Adhesive Elastomers

“…However, current soft synthetic materials suffer from premature failure due to degradation, fracture, and damages from the external environment. Drawing inspiration from nature, supramolecular interactions such as hydrogen bonding, [1,2] metal-ligand coordination, [3,4] π-π stacking, [5] or form three types of hydrogen bonds within the polyurethane network, that is with: 1) polytetrahydrofuran glycol (PTMG) polyol at soft segments; 2) and urethane; and 3) itself to form dimers at hard segments. [23,24] Carboxyl groups have been shown to increase the stretchability and self-healing efficiencies of the urethane-based elastomers in our prior work, despite having limited mechanical toughness and long healing times.…”

“…However, current soft synthetic materials suffer from premature failure due to degradation, fracture, and damages from the external environment. Drawing inspiration from nature, supramolecular interactions such as hydrogen bonding, [ 1,2 ] metal‐ligand coordination, [ 3,4 ] π–π stacking, [ 5 ] or host guest interaction, [ 6 ] have been introduced to polymeric systems to increase toughness and impart self‐healing abilities; allowing both prevention and recovery of damages respectively.…”

A Short Review on Self‐Healing Thermoplastic Polyurethanes

“…The polyurethane could withstand a high tensile stress of 4.6 MPa at a strain of 498%, and a self-healing efficiency reached 96% at room temperature. [78] You et al introduced the dimethylglyoxime-urethane moiety with multiple functions such as room temperature reversible dynamic cleavage, metal coordination, and photolysis into polyurethane materials to obtain an all-in-one protective material with toughness, mechanical gradient, spontaneous self-repair at room temperature, and fluorescent properties at the same time. [79] A new self-healable polyurethane based on multiple H-bonding and zinc-imidazole coordinated bonds was shown to have a high tensile strength and superior stretchability.…”

Preparation of ecofriendly water-borne polyurethane elastomer with mechanical robustness and self-healable ability based on multi-dynamic interactions

“…Dynamic covalent bonds mostly include urea bonds, 15,16 Diels-Alder bonds, 11,17 boronic ester, 12,[18][19][20][21] disulde bonds, [22][23][24] diselenide bonds 25 and phenol-carbamate bonds. 26 Noncovalent interactions include hydrogen bonds, [27][28][29][30][31][32] metalligand coordination, [33][34][35][36][37] ionic interactions, 38,39 host-guest interactions, 40 and p-p stacking interactions. 41,42 However, healing via DA ring addition and phenol-carbamate bonds requires high temperatures of up to 120 °C, which consumes a lot of energy.…”