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The layered nanocomposite hydrogel films containing chitosan (CS) and graphene oxide (GO) have been prepared by water evaporation induced self-assembly and subsequent physical cross-linking in alkaline solution. The layered CS/GO hydrogel films obtained have a nacre-like brick-and-mortar microstructure, which contributes to their excellent mechanical properties. The tensile strength and elongation at break of the hydrogel films with 5wt% GO are 5.35MPa and 193.5%, respectively, which are comparable to natural costal cartilage. Furthermore, the CS/GO hydrogel films exhibited pH-driven shape memory effect, and this unique phenomenon is mainly attributed to the reversible transition of partial physically cross-linking corresponding to hydrogen bondings and hydrophobic interactions between CS polymer chains due to pH changing., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The development of hydrogels combining superior mechanical property attracts researchers' attention in recent years. Here, a novel nanocomposite hydrogel is prepared by one‐step photo‐polymerization of acrylic acid (AA) and N,N‐dimethylacrylamide (DMAA) in the presence of hydroxyapatite nanoparticles (HAp NPs) and aluminum hydroxide nanoparticles (Al(OH)3 NPs). The resulting transparent hydrogel exhibits ultrahigh toughness of 28.3 MJ m−3, high strength of 2.8 MPa, large elongation of 1300%, excellent self‐recovery and good biocompatibility. The crosslinking mechanism is contributed to the ionic coordination interaction between cations absorbing on the surface of nanoparticles and carboxyl groups of the polymer chain, and the synergistic toughening effect between HAp NPs and Al(OH)3 NPs is responsible for improving the strength and toughness simultaneously. Furthermore, this synergistic toughening strategy may provide a universal method for designing and constructing high strength nanocomposite hydrogels in many applications, especially for artificial cartilages. POLYM. COMPOS., 40:942–951, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Various applications of nanocomposite hydrogels with a single crosslinked network have been largely limited by their poor comprehensive mechanical properties, despite their prominence in certain mechanical properties. Here, we introduce ferric ions into titania-based nanocomposite hydrogels to fabricate robust ionic nanocomposite hydrogels (INC gels) with hierarchically crosslinked networks. The introduction of ion crosslinkers into nanocomposite hydrogels dramatically improves their comprehensive mechanical properties. The mechanical attributes can be changed over wide ranges by adjusting hydrogel components and the optimal INC gel exhibits the super high strength of 13.0 MPa, elastic modulus of 26.8 MPa, and toughness of 34.3 MJ m −3 . In addition, The INC gels show a good mechanical and volume stability in saline solutions due to the unique crosslinked network. The reversible phase separation in gels can be used for the achievement of the shape memory effect without significantly destroying the mechanical properties and enable the mussel shell-like hydrogel to imitate the self-protection behaviour of the mussel to grab the bead underwater. Therefore, these hydrogels will hold a great potential in underwater mechanical catching hands. [ABSTRACT FROM AUTHOR]

We developed a simple one-step synthesis route to prepare silver nanoparticles containing nanocomposite hydrogels by in situ free-radical copolymerization of N-isopropylacrylamide and N-(hydroxymethyl) acrylamide. In this synthesis, the hydrogels and nanoparticles are formed simultaneously without any additional reducing agent at room temperature, thus demonstrating the synergetic effect between reductive monomer HMAm and catalytic clay nanosheets in promoting the reduction of silver ions. The in situ generated silver nanoparticles within the hydrogel matrix were highly stable and the hydrogels showed sustained release of silver for periods of at least ten days in aqueous solution. Interestingly, the mechanical properties of the hydrogels showed remarkable improvement upon addition of a small amount of AgNPs. Furthermore, the resulting gels exhibited thermosensitive antibacterial activity, which was enhanced with an increase in the N-isopropylacrylamide content of the copolymers. Our work provides a facile and convenient green approach to preparing antibacterial tough hydrogels, which may find potential applications in wound dressings, tissue engineering and catalysis. [ABSTRACT FROM AUTHOR]

A novel series of nanocomposite hydrogels (TAD gels) with high mechanical strength and excellent UV-shielding property were prepared by in situ free-radical copolymerization of acrylamide (AM) and N, N-dimethylacrylamide (DMAA) in aqueous solutions of TiO2 nanoparticles (TiO2 NPs). It was found that the TiO2 NPs were uniformly dispersed in the copolymer matrix and acted as inorganic crosslinking agents in TAD gels owing to their hydrogen bonding interactions with polymer chains. The TAD gels exhibited excellent mechanical properties such as large elongations at break, high elastic moduli, and ultimate stresses, all of these properties as well as swelling ratios of TAD gels could be easily controlled by changing the AM ratios and TiO2 contents in the initial solutions. In addition, the TAD gels with low AM ratios could be prepared into thin films in a customized Teflon model and these films showed high transparency in visible light but could completely block the UV light with wavelength below 366 nm and prevent the methylene blue from degradation under UV irradiation. POLYM. COMPOS., 37:810-817, 2016. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

• The Al-NC gel exhibits the long-term nonswellable behavior in seawater. • The Al-NC gel has exceptional mechanical properties in seawater. • The structured Al-NC gel holds the long-term stable surface morphology in seawater. • The structured Al-NC gel has the durable oil-repellent property in seawater. Hydrogels, intrinsic hydrophilic materials, have been extensively used for fabrication of underwater superoleophobic substrates. However, the swelling behavior, poor salt tolerance and weak mechanical properties of hydrogels in high-salinity marine environment have significantly negative impacts on underwater oil-repellent effect. Herein, an ultrastrong hydrogel maintaining long-term volume stability in seawater is developed by introducing strong coordination interactions between nanoparticles and polymer matrix. The tensile strength, elastic modulus, and compressive strength of this nonswellable hydrogel are up to 9.2 MPa, 52.3 MPa and 48.5 MPa respectively, superior to those of all other reported underwater superoleophobic hydrogels. After introducing lotus-leaf-like micro/nanostructures on this nonswellable hydrogel, the structured surface demonstrates durable superoleophobicity and ultralow oil adhesion (less than 1 μN) under seawater. Notably, the 3D optical images and SEM images reveal that lotus-leaf-like micro/nanostructures on the nonswellable hydrogel surface can be well preserved even after immersion in seawater for one year, enabling the nonswellable structured hydrogel still to show anti-crude-oil-adhesion property under seawater. [ABSTRACT FROM AUTHOR]