Exploring Self‐Healing and Switchable Adhesives based on Multi‐Level Dynamic Stable Structure

Abstract

According to actual needs, the adhesives can achieve switchable attachment to material surfaces and subsequently reuse. [7,8] Introducing dynamic bonds into the molecular structure is an effective way to develop switchable adhesives due to their designability and reversibility. Upon exposure to an appropriate stimulus, dynamic bonds will undergo reversible breaking to realize the topological rearrangements of the network, resulting in the decrease of modulus (viscosity) along with the loss of adhesive properties. [9] While the external stimulus is removed, the dynamic bonds between the polymer segments can recombine to form the initial state, simultaneously recovering the outstanding adhesive properties. [10,11] Saito et.al incorporated dynamic boronic ester bonds into commodity triblock thermoplastic elastomers to prepare switchable/recyclable adhesive materials that exceptionally have high adhesion strength and can be debonding and re-bonding via hot pressing. [12] Furthermore, Li et al. prepared dynamic hydrogen-bonded cross-linked hydrogels with humic acid and polyvinylpyrrolidone, processing good adhesion properties and broad application as hemostatic agents. [13] Although great efforts have been made in the development of switchable adhesives, most switchable adhesives are only controlled by a single stimulus, greatly affecting their switching speed and switch efficiency. [14,15] Additionally, these adhesives are still facing the challenge of remaining good stability when exposed to repeated mechanical deformation, which greatly influences their durability, reliability, and lifetime. Thus, it is vital to develop multifunctional switchable adhesives with strong adhesion, multiple efficient switchable performance, and autonomous self-healing.It has been shown that mussels can strongly cling to a variety of material surfaces, such as rocks, ships, and other media, after withstanding the force of the constant pounding waves (Figure 1a). Recently, 3,4-dihydroxyphenylalanine extracted from mussel foot protein was proven to be the key to good adhesion ability, due to its unique ability to form multi-interac tion with various matrices. [16,17] Especially, the catechol group can form a strong complex with metal ions (Fe 3+ , Cu 2+ , Ti 3+ ) with long stability constant higher than 40 (even comparable It is a challenge to develop adhesives simultaneously capable of strong adhesion and efficient switchable ability. Herein, the authors report multifunctional switchable adhesives named Cu 2+ -curcumin-imidazole-polyurethane (CIPUs:Cu 2+ ) by introducing 1-(3-aminopropyl) imidazole and curcumin into polyurethane system crossed by Cu 2+ forming dynamic metal-ligand bonds. This CIPUs:Cu 2+ has strong adhesion (up to 2.46 MPa) on various material surfaces due to their specially designed functional groups alike the secretions from mussels. It can achieve fast switching speed (30 s) and high switch efficiency through multiple contactless remote stimulations. Importantly, density functional theory (DFT) calculation reveals tha...

Controllable Synthesis of Furan-Based Poly(ester amide)s and Its Study on Adhesive and Aggregation-Induced Emission Properties

“…A schematic illustration of the lap shear adhesion test and the lap shear strength is presented in Figure 4b. PEA 1.2 showed a lap shear strength of 2.0 MPa, which was comparable to the recently reported adhesives, such as isocyanate-free polyurea, 29 Cu 2+ −curcumin−imidazole−polyurethane, 30 oxidized sucrose-polyamines adhesive. 31 While increasing the DMFDCA/DP feed ratio, the lap shear strength of PEAs gradually decreased, which might be due to its lower cross-linking network and intermolecular force.…”

Robust Dynamic Epoxy Adhesives with High Environmental Tolerance Enabled by the Coordination of Small-Molecule Coupling Agents with Boroxine

“…Epoxy adhesives (EAs) with high adhesion strength (>10 MPa) are widely used in our daily lives due to their ability to assemble different structures into finished products with high reliabilities. − However, these finished products are hard to dismantle or recycle once fabricated, , which strictly limits their sustainability in modern fields including construction, automobile, and aerospace. − While variable detachable polymeric adhesives based on photoisomerization reactions, multiple dynamic bonds, and thermally responsive polymers have been reported, − these polymers usually show rather low adhesion strength compared with structural epoxy adhesives. Thus, developing dynamic epoxy adhesives (DEAs) with simultaneously strong adhesion, extreme environmental tolerance, and on-demand detachability is in high demand in the future.…”

Multidynamic Poly(oxime–carbamate) Elastomers with Rosin Moieties

“…In particular, the Cu-RPOUT elastomer (0.3080 g, 40.0 mm (length) × 10.0 mm (width) × 0.7 mm (thickness)) could successfully lift a weight of 10 kg (Figure S4). Compared with existing elastomers based on metal coordination bonds, the Cu-RPOUT elastomer exhibits excellent mechanical strength (Figure b). − These results suggest that the mechanical properties of the material can be improved after the formation of multicross-linking structures (hydrogen, metal–ligand coordination, and oxime–carbamate bonds) in the material, suggesting that the hydrogen and metal–ligand coordination bonds can be used as dynamic cross-linking points to increase the cross-linking density of the material. , This leads to further energy dissipation, which leads to the strengthening and toughening of the elastomers …”