A novel type of physical hydrogel based on dual-crosslinked strategy is successfully synthesized by micellar copolymerization of stearyl methacrylate, acrylamide, and acrylic acid, and subsequent introduction of Fe 3+ . Strong hydrophobic associations among poly(stearyl methacrylate) blocks form the first crosslinking point and ionic coordination bonds between carboxyl groups and Fe 3+ serve as the second crosslinking point. The mechanical properties of the hydrogel can be tuned in a wide range by controlling the densities of two crosslinks. The optimal hydrogel shows excellent mechanical properties (tensile strength of ≈6.8 MPa, elastic modulus of ≈8.0 MPa, elongation of ≈1000%, toughness of 53 MJ m −3 ) and good self-recovery property. Furthermore, owing to stimuli responsiveness of physical interaction, this hydrogel also shows a triple shape memory effect. The combination of two different physical interactions in a single network provides a general strategy for designing of high-strength hydrogels with functionalities.
Smart reconfigurable metamaterials can better adapt to changing electromagnetic environments and broaden the range of applications. However, constructing electromagnetic reconfigurable metamaterials, especially those with large areas or applied to complex surfaces via a universal approach, is still a challenge. Here, we introduce a smart reconfigurable metamaterial consisting of a thermadapt shape memory polymer ethylene vinyl acetate copolymer (EVA) matrix and a flowable liquid–metal resonant unit. Based on the excellent self-healing properties of EVA, large-area metamaterials can be constructed by thermal assembly of metamaterial units. In addition, the original shape of the metamaterial can be reprogrammed to apply to complex three-dimensional surfaces with the reprocessing properties of EVA. Moreover, by utilizing the shape memory performance of the EVA, the temporary resonant frequency of the metamaterial can be set by programming and the resonant frequency tuning of the metamaterial can be controlled under external temperature stimulation, achieving noncontact tuning. In the future, this concept can be broadly applied in fields such as complex structure stealth layers and multifunction filters.
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