A series of self-healing waterborne polyurethane (WPU) films utilizing reversible covalent bond acylhydrazones diol (PA) as chain extender were successfully synthesized. The self-healing performance of WPU with different content of chain extender PA has been systemically characterized via cut-and-healing tests and mechanical quantitative evaluation. The film can repair cracks through acylhydrazone exchange reactions within 12 h. When the content of PA is 1.5 wt%, the WPU has the highest self-healing efficiency of 90.5%. Meanwhile, the effect of PA mass fraction on the particle size distribution, mechanical ability, crystallization, water resistance properties, and thermal stability of WPU were evaluated. With the introduction of acylhydrazone bonds, the hydrophobicity of the WPU material was enhanced, while achieving self-healing performance, which solves the problem of aging and replacement of materials. These results indicated that the self-healing WPU exhibited great application prospect as a versatile material.acylhydrazones, reversible covalent bond, self-healing, waterborne polyurethane | INTRODUCTIONPolyurethane (PU) is extensively applicable polymer materials, and it has been broadly used in various fields such as adhesives, foam materials, elastomers biomaterials, and so forth due to its excellent mechanical property, desirable molecular adaptability and good processing ability. However, the development of traditional PU products has been limited because of the utilization of organic solvents. Waterborne polyurethane (WPU) materials possess the excellent properties as those of traditional PU products have, such as outstanding mechanical property, excellent flexibility and multi-adaptability. Meanwhile, WPU materials are low toxicity and reduced

Waterborne polyurethane (WPU) coating, as a kind of green product, can replace solvent polyurethane coating, but its application in the field of coating is limited since its defects such as slow curing efficiency, low strength, and water resistance. In this study, a trifunctional itaconic acid-based crosslinking agent (IHA) was synthesized from itaconic acid and hydroxyethyl acrylate. A series of green UV-curable WPU coatings were prepared by introducing IHA into WPU prepolymer in different proportions (2.5 $ 10 wt.%). IHA posed as crosslinking agent in WPU, which can not only enhance strength, but also accelerate curing rate in WPU coatings. The results demonstrated that the gel content and hydrophobic angle of the modified WPU coating (WPU-IHA) are increased by 25.6% and 34.8 , respectively, indicating a good water resistance.Most notably, due to the increase of crosslinking degree and the decrease of chain mobility, the UV-curable WPU coating shows excellent mechanical properties with 21.9 MPa in tensile strength and a pencil hardness of 5H, which is substantially higher than that of pure WPU coatings. Therefore, the IHA shows great potential to substitute petroleum-based crosslinking agents in the preparation of environmentally friendly UV-curable WPU coatings with high strength and good surface scratch hardness.

Oxygen evolution reaction (OER) is considered as a critical half-cell reaction of water splitting, the kinetics of which is sluggish even not favored, thus requiring highly active electrocatalysts to shrink the reaction energy barrier and improve the energy conversion efficiency. In this study, In-situ generated trimetallic molybdate nanoflowers on Ni foam by a straightforward and time-saving solvothermal method assisted with microwave, not only bring synergistic effect into full play between multiple metals, but also construct a well-defined nanoflower-like structure accompa-nied by larger specific area (273.3 m 2 g À 1 ) and smaller size than the pristine NiMoO 4 . The resulting Ni 0.9 Al 0.1 MoO 4 -NF requires a relatively low overpotential of 266 mV for OER at 10 mA cm À 2 , which outperforms commercial RuO 2 catalysts (274 mV). Such excellent performance compares favorably to most previously reported NiMoO 4 -based electrocatalysts for OER. This work not only supplies a facile method to construct a well-defined nanoflower-like structure on foam, but also broadens our horizons into the mechanism of OER in alkaline conditions.

Waterborne polyurethane (WPU) is an environmentally friendly material using water as dispersion medium. However, it is significantly restricted that most of the soft segments in WPUs come from oil. In this work, environmentally friendly and low‐cost castor oil is used as the soft segment of polyurethane, and KH550 modification could improve the thermal stability and flexibility of CWPU. The results show that the particle size of the modified CWPU nano‐emulsion gradually increased to 60.48 nm. Through FTIR and XPS analysis, KH550 is successfully introduced into the castor oil‐based waterborne polyurethane system. After the CWPU‐3% film is treated with NaCl, NaOH, HCl solution and high temperature, the groups in the system remain unchanged which shows CWPU‐3% film having good chemical resistance and high temperature resistance. When the addition amount of KH550 is 3%, the maximum contact angle of the CWPU film was 92.39° which reveals good hydrophobic property. The tensile strength of the films increased from 10.2 MPa to 12.8 MPa, and the elongation at break decreased from 841.3% to 658.9%. The thermal stability of the CWPU films modified by KH550 were also improved. The modified CWPU film has excellent hydrophobicity, chemical resistance and temperature resistance.

Oxygen evolution reaction (OER), as the rate-determining step of electrochemical water splitting, is extremely crucial, thus it is a requisite to engineer feasible and effective electrocatalysts to shrink the reaction...