No abstract

Hydrophobic association (HA) hydrogels have recently attracted much attention since they exhibit high selfhealing ability, remolding capability and shape-memory behavior simultaneously, but their low mechanical strength prevents them from use in many stress-bearing applications. In this work, we describe a novel method for the production of tough and highly stretchable hydrogels with self-healing behavior, tensile strength of 150-300 kPa and stretch at break of 2400-2800%. Dual physical cross-linking (DPHF) hydrogels were prepared via micellar copolymerization of acrylic acid (AA) and stearyl methacrylate (C18) in an aqueous ferric chloride solution with two different types of surfactant, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzene sulfonate (SDBS). The mechanical, rheological, selfhealing and swelling properties of the DPHF hydrogels were investigated and also evaluated as a function of the type of surfactant and the content of ferric ions. The introduction of a moderate content of ferric chloride endowed the hydrogels with excellent strength and self-healing properties simultaneously. Moreover, the structure of the DPHF hydrogels was investigated by IR and SEM analysis.The results were consistent with the results of the mechanical, self-healing and swelling properties tests.

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Iron chloride has been found to be an efficient catalyst for the disproportionation of allylic alcohols, which provides a convenient method for selective transformation of allylic alcohols to alkenes and alpha,beta-unsaturated ketones. Furthermore, this catalytic system is also effective for highly selective allylic reduction of allylic alcohols, allylic ethers, and allylic acetates with benzyl alcohol under neutral and convenient reaction conditions.

For graphene oxide (GO) composite hydrogels, a two-dimensional GO material is introduced into them, whose special structure is used to improve their properties. GO contains abundant oxygen-containing functional groups, which can improve the mechanical properties of hydrogels and support the application needs. Especially, the unique-conjugated structure of GO can endow or enhance the stimulation response of hydrogels. Therefore, GO composite hydrogels have a great potential in the field of wearable devices. We referred to the works published in recent years, and reviewed from these aspects: (a) structure of GO; (b) factors affecting the mechanical properties of the composite hydrogel, including hydrogen bond, ionic bond, coordination bond and physical crosslinking; (c) stimuli and signals; (d) challenges. Finally, we summarized the research progress of GO composite hydrogels in the field of wearable devices, and put forward some prospects.

An efficient method for the formation of SiCl3 radicals by the reaction of abundant and cheaper chlorosilanes with DyI2 has been established, not only demonstrating new distinctive reactivities of solvated DyI2 but also suggesting that the presence of lanthanide ions can improve the selectivity of some silyl radical-catalyzed reactions.

No abstract

Intelligent hydrogels with excellent flexibility, biocompatibility, and stimulus responsivity can mimic the functions of the skin to detect human motions. However, the low mechanical strength limits its application in the field of biomimetic materials. In this work, polyacrylamide‐reduced graphene oxide (PAM‐rGO) composite hydrogels were prepared by the combination of PAM and partially rGO, and their biomimetic strain sensors were studied. The rGO played the role of “2D flexible crosslinking point” in the composite hydrogel. Through the H‐bonds between rGO and hydrogels, the toughness and strength of the composite hydrogel were enhanced. The maximum strain of the hydrogel changed from 751% to 1097%, and the maximum stress changed from 0.065 to 0.20 MPa. On the other hand, the interaction between the PAM backbone and the rGO provided a credible resistance response to the stimulation of strain. The better linear relationship between resistance and length was built, with R2 of 0.992. Furthermore, the composite hydrogels were assembled into wearable devices to monitor human‐motion, including fingers bending, elbows bending and walking. The experimental results showed that the PAM‐rGO composite hydrogel had great potential in the field of bionic skin.