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Large amplitude oscillatory shear (LAOS) test has been used to elucidate the nonlinear viscoelastic behaviors of soft matter or complex fluids under large and rapid deformations encountered in production and application, especially for most polymeric materials. In this work, combined with recovery rheology, the physical visualization of the start and end yield stress values of yield stress fluids determined by the algebraic stress bifurcation (ASB) method is further interpreted in extenso. Facing the issue of unrecoverable deformations that may occur below the yield stress, the ASB method suggests the start and end yield stresses by considering the timescale, thereby linking the yield stress determination and nonlinear behavior analysis in LAOS. The unusual sharp corners in the Lissajous curves induced by the Kamani–Donley–Rogers (KDR) model are also revealed and treated by viscosity regularization. The correlation among the yield points determined by ASB and stress bifurcation, the responses of the KDR model, and corresponding results and insights by main LAOS analyses in representative cases are comprehensively discussed. This work contributes to a new understanding of stress bifurcation. [ABSTRACT FROM AUTHOR]

A facile strategy is developed to fabricate a two‐layer grafted polymer coatings on silicon wafers, specifically soft crosslinked polythioether as middle damping layer and stiff poly(methyl methacrylate) (PMMA) as top protecting layer. At first, a highly crosslinked polythioether layer was constructed on the surface of the silicon wafer with tunable thickness and smooth morphology with trimethylolpropane tris(2‐mercaptoacetate) and pentaerythritol triallyl ether as monomers and 4‐(N,N‐diphenyl‐amino)benzaldehyde as an organocatalyst. The Young's modulus of the grafted crosslinked polythioether layer is about 300–400 MPa and the roughness is about 11.3 nm measured by atomic force microscope. There are about 9000 ea reactive –SH in a cuboid cell with 1 nm2 base area and 7–14 μm height in the grafted crosslinked polythiolether layer. Then, a flatten PMMA coating layer with Young's modulus as high as ~2.4 GPa was grafted from/onto the surface of the crosslinked polythiolether with surface –SH groups as initiating or chain transfer sites. [ABSTRACT FROM AUTHOR]

Developing low-cost and highly active hydrolysis catalytic materials for the dehydrogenation of hydrogen-rich chemicals is a promising strategy to store and easily release hydrogen for fuel cell applications. In this study, new bimetallic hybrid nanoplates containing Co3O4 and CuCoO2 were developed via a facile and low-cost approach for catalytically producing hydrogen from ammonia borane (NH3BH3). The as-prepared efficient Co3O4–CuCoO2 material was employed as a catalyst for NH3BH3 hydrolysis, and it exhibited a high catalytic performance with a turnover frequency (TOF) of 65.0 molhydrogen molcat.−1 min−1 at room temperature. The results revealed that the hybrid Co3O4–CuCoO2 catalysts exhibited much improved catalytic activity towards the hydrolysis reaction in contrast to the individual Co3O4 and CuCoO2 catalysts. A kinetic study showed that the Co3O4–CuCoO2 catalytic material had superior activity with an apparent activation energy (Ea) of 20.5 kJ mol−1, which was found to be one of the lowest Ea for NH3BH3 hydrolysis ever reported in the literature. This work provides a promising approach for the synthesis of noble metal-free catalysts exhibiting high catalytic activity towards NH3BH3 hydrolysis. [ABSTRACT FROM AUTHOR]

This contribution presents a versatile strategy to transfer unactivated surface C–H bonds of polymeric substrates to C–R–F groups (R stands for a spacer and F stands for functional group) by UV light‐assisted surface free radical coupling. With p‐dimethylaminophenyl radical as a building block, various reactive groups, such as –CHO, –SH, –B(O)OH, –CN and –SO3−, are successfully grafted onto typical commercial polymer substrates including biaxially oriented polypropylene, polyethylene phthalate, ethylene tetrafluoroethylene copolymer and dimethyl silicone rubber. Fluorencence microscope images, X‐ray photoelectron spectroscopy, UV‐vis and fluorescence spectra support that the above functional groups are covalently bonded to the polymer substrates. The concentration of the reactive groups immobilized on the different substrates is in the order of 10−8 to 10−7 mmol mm−2 determined by UV‐vis spectrometry. In addition, as a proof‐of‐concept, the introduced functional groups are demonstrated by their special reactions, for example, –CHO reacting with –NH2 to synthesize Schiff base, –SH to detect silver ions, and the complexes of –C=N and Zn2+ to degrade Rhodamine B. The results indicate that one can fabricate an integrated molecular library on the surface of polymeric substrates at the molecular level by selecting the building blocks. [ABSTRACT FROM AUTHOR]

We have built a high-performance supercapacitor anode based on carbon fabric (CF), vertically aligned graphene nanosheets (VAGN) and FeOOH nanorods. This CF/VAGN/FeOOH electrode can charge/discharge at a low potential window (0 to −1.1 V vs. Hg/HgO), and demonstrates a high specific capacitance of 909 F g−1 aided by the unique structure of VAGN. Additionally, we made an all-solid-state asymmetric supercapacitor by assembling CF/VAGN/FeOOH and CF/Co3O4 electrodes. The asymmetric design broadens the working potential up to 1.7 V, leading to a high energy density of 33 W h kg−1 and a high power density of 26 kW kg−1. We believe that the CF/VAGN/FeOOH electrode holds great promise for applications in high-performance asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

A facile synthetic route was developed to prepare a surface-grafted brush layer of poly(vinyl ethers) (PVEs) directly by a radical mechanism, with the "naked" Li + acting as a catalyst. Density functional theory calculations suggested that complexation of naked Li + to VEs significantly reduced the highest unoccupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap from 5.08 to 0.68 eV, providing a better prospect for electron transfer. The structure, morphology, and surface properties of grafted polymer layers were characterized using attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and dynamic water contact angle (DCA). Moreover, ellipsometry data indicated that the thickness of the polymer brushes was in the range of 20-60 nm, which corresponds to the grafting densities of 0.65-1.15 chain/nm 2 , and DCA decreased from 84.4 to 45.3°. Most importantly, no hydrolysis was observed for the modified surface after 30 days of exposure to phosphate-buffered saline solution, 0.1 mol/L NaOH(eq) and 0.1 mol/L HCl(eq), demonstrating excellent hydrolysis resistance with long service life. In addition, as a proof of concept, the side hydroxyl groups of grafted PVEs provide active sites for efficient fixation of bioactive molecules, e.g., glycosaminoglycan and serum protein.