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Abstract Hydrogels in water or aqueous solutions swell or shrink unidirectionally until reaching an equilibrium state, which has been extensively studied through both experimental analysis and theoretical prediction. In this work, an unexpected concurrent swelling and deswelling behavior of hydrogels is reported, which manipulates the water state in the polymer networks. The osmotic pressure‐driven rapid deswelling and the ionic electrostatic repulsion‐driven slow swelling of hydrogels occur simultaneously, affording double‐layered polyacrylamide (PAM) hydrogels, in which the rigid inner layer does not contains free water, while the soft outer layer comprises both bound and free water. The PAM hydrogels show uniaxial tensile fracture strengths and Young's moduli up to 104.2 MPa and 2.4 GPa, respectively, outperforming various polymeric and biological structural materials. This strategy is applicable to the general molding and three‐dimensional (3D) printing techniques, providing wide possibilities for engineering applications. Such strong and rigid hydrogels can simultaneously serve as structural materials for load‐bearing and act as functional materials for super‐stress (25 to 6000 N) and highly adaptable tactile sensing. These findings enrich the hydrogel swell/deswelling theory and broaden the engineering applications of hydrogels as structural materials.
Interfacial engineering of cost-effective non-noble materials is attractive for synthesizing advanced electrocatalysts toward hydrogen evolution reaction (HER). Herein, we prepare N, S-doped Mo 2 C-Mo/C heterogeneous nanorods (NSMB-1.25) with abundant active heterointerfaces and defect sites via in situ polymerization and carburization strategy. The polyaniline-derived heteroatom-doped carbon acts not only as a matrix but also as a carbon source for Mo 2 C formation. The phase transition of Mo 2 C-Mo heterostructure is accurately regulated by delicately varying the dosage of polymerization initiator and calcine temperature. The synergistic effects of Mo 2 C, metallic Mo and N, S doping carbon significantly enhance the HER activity and durability of nanorods. Benefiting from the plentiful active sites of the Mo 2 C-Mo heterointerfaces, fast charge and mass transfer channels, heteroatomic doping and large surface area, the as-prepared NSMB-1.25 nanorods deliver only 118 mV overpotential at 10 mA cm -2 current density, small Tafel slopes of 74.38 mV dec -1 , high exchange current density of 25.84 ´ 10 -2 mA cm -2 and excellent stability in 1.0 M KOH solution. This work may support a feasible strategy to the rational design of high-active heterogeneous carbon-based electrocatalysts for efficient energy conversion and storage.
Abstract Polyurethane is a promising topcoat in anticorrosive coating system. As a topcoat, the study on improving its weathering resistance is significative. In this work, we present an anticorrosive filler, named GOFA based on p‐fluoroaniline chemical modified graphene oxide, and explored the potential of GOFA to improve the weatherability and corrosion resistance of polyurethane coatings. The results of the comprehensive experimental studies showed that the addition of 0.5 wt.% GOFA leaded to an improvement in the hydrophobicity of the polyurethane coating and the composite coating exhibits an excellent shielding effect against corrosive media. At the same time, the ultraviolet aging resistance the GOFA modified polyurethane composite coating also showed satisfactory results. It is inspired that adding a small amount of GOFA can make the composite polyurethane coating have excellent anti‐corrosion performance and weather resistance.
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