A Tough Hydrogel Adhesive for the Repair of Archeological Pottery

Mechanical Robust GO/PVA Hydrogel for Strong and Recyclable Adhesion in Air, Underwater, and Underoil Environments

Adhesive hydrogels are considered to be promising interfacial adhesive materials for various applications; however, their adhesive strength is significantly reduced when immersed in liquid environments (water and oil) due to obstruction of the liquid layer or swelling in liquid, and they could not always be reused when the failure of the adhesive performance occurred. Herein, a graphite oxide/poly(vinyl alcohol) (GO/PVA) hydrogel with strong adhesion in air and under liquid environments was developed by rationally regulating the interactions of water and dimethyl sulfoxide (DMSO) in the binary liquid system. The strong interaction between water and DMSO allowed the water layer of the GO/PVA hydrogel on the hydrogel surface to act as a shield to repel oil in air, under water, and even when immersed in oil, and it also endowed the obtained hydrogel with antiswelling property when immersed in water and oil. Importantly, the GO/PVA hydrogel could serve as an advanced adhesive to firmly bond different substrates in air, under water, and under oil, and interestingly, its dry and wet adhesive performance was repeatable and recyclable. This work is expected to be an important addition to the field of adhesive soft materials.

Peeling-Stiffening Self-Adhesive Ionogel with Superhigh Interfacial Toughness

Self-adhesive materials that can directly adhere to diverse solid surfaces are indispensable in modern life and technologies. However, it remains a challenge to develop self-adhesive materials with strong adhesion while maintaining its intrinsic softness for efficient tackiness. Here, a peeling-stiffening self-adhesive ionogel that reconciles the seemingly contradictory properties of softness and strong adhesion is reported. The ionogel contains two ionophilic repeating units with distinct associating affinities, which allows to adaptively wet rough surface in the soft dissipating state for adhering, and to dramatically stiffen to the glassy state upon peeling. The corresponding modulus increases by 117 times driven by strain-rate-induced phase separation, which greatly suppresses crack propagation and results in a super high interfacial toughness of 8046 J m-2 . The self-adhesive ionogel is also transparent, self-healable, recyclable, and can be easily removed by simple moisture treatment. This strategy provides a new way to design high-performance self-adhesive materials for intelligent soft devices.

Temporary Consolidation of Marine Artifact Based on Polyvinyl Alcohol/Tannic Acid Reversible Hydrogel

Underwater artefacts are vulnerable to damage and loss of archaeological information during the extraction process. To solve this problem, it is necessary to apply temporary consolidation materials to fix the position of marine artifacts. A cross-linked network hydrogel composed of polyvinyl alcohol (PVA), tannic acid (TA), borax, and calcium chloride has been created. Four hydrogels with varying concentrations of tannic acid were selected to evaluate the effect. The hydrogel exhibited exceptional strength, high adhesion, easy removal, and minimal residue. The PVA/TA hydrogel and epoxy resin were combined to extract waterlogged wooden artifacts and marine archaeological ceramics from a 0.4 m deep tank. This experiment demonstrates the feasibility of using hydrogel for the extraction of marine artifacts.

Stretchable, Adhesive, and Biocompatible Hydrogel Based on Iron-Dopamine Complexes

Hydrogels' exceptional mechanical strength and skin-adhesion characteristics offer significant advantages for various applications, particularly in the fields of tissue adhesion and wearable sensors. Herein, we incorporated a combination of metal-coordination and hydrogen-bonding forces in the design of stretchable and adhesive hydrogels. We synthesized four hydrogels, namely PAID-0, PAID-1, PAID-2, and PAID-3, consisting of acrylamide (AAM), N,N'-methylene-bis-acrylamide (MBA), and methacrylic-modified dopamine (DA). The impact of different ratios of iron (III) ions to DA on each hydrogel's performance was investigated. Our results demonstrate that the incorporation of iron-dopamine complexes significantly enhances the mechanical strength of the hydrogel. Interestingly, as the DA content increased, we observed a continuous and substantial improvement in both the stretchability and skin adhesiveness of the hydrogel. Among the hydrogels tested, PAID-3, which exhibited optimal mechanical properties, was selected for adhesion testing on various materials. Impressively, PAID-3 demonstrated excellent adhesion to diverse materials and, combined with the low cytotoxicity of PAID hydrogel, holds great promise as an innovative option for biomedical engineering applications.