23 MPa), despite its exceptionally high water content (i.e., 90 wt%). The integration of such unprecedented mechanical attributes is mainly ascribed to the exquisite multilayered lamellar structures consisting of aligned chitin nanofibers. [5,6] However, when compared with natural materials, conventional synthetic hydrogels are typically weak and fragile for practical applications, owing to the sparsely crosslinked network, low solid content, homogeneous structure, and absence of structural hierarchy, thus hampering their practical applications where long service life, high loading capability and/or impact tolerance are highly demanded. [7][8][9][10] One of the most promising approaches to engineer synthetic hydrogels with extraordinary mechanical properties (i.e., strength, modulus, toughness and fatigue resistance) is through the bioinspired structural hierarchy design. [10][11][12][13][14][15][16][17] The most spectacular examples are nacre-like polymer or hydrogel composites, which are consisted of aligned micro/nanoparticles in a polymer matrix, thus, enabling them stiff yet tough and able to dissipate energy. [5,[18][19][20][21][22][23] In addition to the layered and brick-and-mortar microstructures, high inorganic loading (i.e., >70 wt%) is another critical role for the mechanical enhancement, however, sacrificing With the strengthening capacity through harnessing multi-length-scale structural hierarchy, synthetic hydrogels hold tremendous promise as a low-cost and abundant material for applications demanding unprecedented mechanical robustness. However, integrating high impact resistance and high water content, yet superior softness, in a single hydrogel material still remains a grand challenge. Here, a simple, yet effective, strategy involving bidirectional freeze-casting and compression-annealing is reported, leading to a hierarchically structured hydrogel material. Rational engineering of the distinct 2D lamellar structures, well-defined nanocrystalline domains and robust interfacial interaction among the lamellae, synergistically contributes to a record-high ballistic energy absorption capability (i.e., 2.1 kJ m −1 ), without sacrificing their high water content (i.e., 85 wt%) and superior softness. Together with its low-cost and extraordinary energy dissipation capacity, the hydrogel materials present a durable alternative to conventional hydrogel materials for armor-like protection circumstances.
Porous hydrogels, possessing both high mechanical strength and high permeability, are sought after in energy storage, soft robotics, solar vapor generation, and tissue engineering. However, there is always a trade-off between mechanical strength and permeability. In general, high porosity promotes molecular mass transportation (permeability) but sacrifices mechanical strength. To address this issue, in this work, micro/nanoporous hydrogels with high mechanical strength are fabricated from the self-assembly of amphiphilic triblock copolymers consisting of hydrophilic end blocks and hydrophobic midblocks. The chemically distinct blocks induce the phase separation, yielding a hydrogel network consisting of nanopores dispersed in the micrometer-thick sponge-like base support with an ordered lamellar structure. The soft water-depleted phase is dynamic, forming a transient network that allows chain exchange and coalescence between different phases. This reversible process not only dissipates energy to toughen hydrogels but also enables self-recovery. By systematically altering the length of end blocks and midblocks, one can synthesize hydrogels with tunable mechanical properties, including an elastic modulus of 87–884 kPa, a fracture stress of 63–584 kPa, a fracture strain of 1–20, and work of extension of 217–2104 kJ/m3. The gels with a porous size in the range of 1–8 μm also exhibit self-recovery behavior and a high permeability of 10–12 and 10–11 m2. The porous hydrogels show a fracture energy of ∼2000 J/m2, several orders of magnitude higher than common porous hydrogels (gelatin, agarose, and polyacrylamide) and comparable to soft biological tissues. The preparation process also endows the foreseeable potential as injectable hydrogels for applications in soft robotics and 3D printing.
BmNPV is a severe pathogen that infects mainly Bombyx mori , a domesticated insect of economic importance, and accounts for approximately 15% of economic losses in sericulture. BV production plays a key role in systemic BmNPV infection of larvae.
Strong adhesives as structural load-bearing materials can provide both adhesive bonding to substrate surfaces and cohesive bonding throughout the bulk material, which are widely used in the cement nail, electronic device, and automotive industries. By a molecular topological regulation, in this work, we developed a series of strong adhesives based on comb-like polymers. By systematically regulating the topological parameters including the side chain length, the spacer between side chains, and the degree of polymerization of the overall backbone, comprehensive studies on linear rheology (the terminal relaxation time and zero viscosity) and non-linear debonding adhesion (the work of adhesion) are performed on these comb-like polymers. It was found that the rheological behaviors depend not only on the structure parameters but also on whether or not the samples exhibit phase separation. Moreover, regardless of the topological structure of comb-like polymers with strong and weak phase separation, the universal work of adhesion is observed to be dependent on the multiplication of terminal relaxation time and the debonding rate, indicating dynamic control over the nonlinear work of adhesion. Furthermore, comb-like polymers are feasible to bind with diverse substrates, including glass, polypropylene and polyethylene terephthalate, wood, and metal. In comparison to existing works using dynamic physical or chemical bonds, molecular topology regulation is more easily fulfilled in strong adhesives without the use of additives and complicated chemical and physical modifications, lowering the barrier for practical applications.
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