High-strength hydrogels:Fabrication,reinforcement mechanisms,and applications

With the continuous appearance and expansion of high-strength hydrogels in emerging fields such as industry,medicine,and green development,the synthesis and application of high-strength hydrogels have developed dramatically and achieved remarkable results from the aspects of raw materials,preparation methods,and reinforcement mechanisms.However,there is still a lack of systematic reviews on high-strength hydrogels.Herein,we first discuss the advantages of natural and synthetic materials,and the characteristics of high-strength hydrogels prepared from different raw materials;we then expound on the influence mechanism of physical interactions or chemical bonds on the strength of the hydrogel from three aspects:physical cross-linking,chemical cross-linking,and dynamic chemical cross-linking;at last,we systematically expound the strengthening strategies,including double network/multi-network,nanocomposite,topology,supramolecular polymerization,and characteristics and strengthening mechanisms of such high-strength hydrogels.In addition,based on the development status of high-strength hydrogels,we combined the application requirements and the existing drawbacks of high-strength hydrogels to propose their possible development directions in the future.

Bioinspired Adaptive Gel Materials with Synergistic Heterostructures

In nature, many biological soft tissues with synergistic heterostructures, such as sea cucumbers, skeletal muscles and cartilages, exhibit high functionality to adapt to complex environments. In artificial soft materials, hydrogels are similar to biological soft tissues due to the unique integration of ＂soft and wet＂ properties and elastic characteristics. However, currently hydrogel materials lack their necessary adaptability, including narrow working temperature windows and uncontrollable mechanics, thus restrict their engineering application in complex environments. Inspired by abovementionedbiological soft tissues, researchers have increasingly developed heterostructural gel materials as functional soft materials with high adaptability to various mechanical and environmental conditions. This article summarizes our recent work on high-performance adaptive gel materials with synergistic heterostructures, including the critical design criteria and the state-of-the-art fabrication strategies of our gel materials. The functional adaptation properties of these heterostructural gel materials are also presented in details, including temperature, wettability, mechanical and shape adaption.