Impact of carbon coating thickness on the electrochemical properties of Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C composites

A series of Li₃V₂(PO₄)₃/C composites with different amounts of carbon are synthesized by a combustion method. The physical and electrochemical properties of the Li₃V₂(PO₄)₃/C composites are investigated by X-ray diffraction, element analysis, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and electrochemical measurements. The effects of carbon content of Li₃V₂(PO₄)₃/C composites on its electrochemical properties are conducted with cyclic voltammetry and electrochemical impedance. The experiment results clearly show that the optimal carbon content is 4.3 wt %, and more or less amount of carbon would be unfavorable to electrochemical properties of the Li₃V₂(PO₄)₃/C electrode materials. The results would provide some basis for further improvement on the Li₃V₂(PO₄)₃ electrode materials.     

Four Mixed 3d-4f 12-Metallacrown-4 Complexes: Syntheses,Structures and Magnetic Properties

The incorporation of Ln^III ions into the 12-metallacrown-4 topology affords the formation of four mixed 3d-4f pentanuclear complexes of compositions [NH(C₂H₅)₃]{[Ln(OAc)₄] [12-MC _Mn ^III _(N)shi-4]}·xH₂O (Ln = Sm (1), Gd (2), Tb (3), Dy (4); x = 0.5 for 1 and 3, x = 0.25 for 2, x = 0 for 4; H₃shi = salicylhydroxamic acid). Compounds 1–4 were obtained from the reactions of H₃shi with Mn(CH₃COO)₂·4H₂O and Ln(NO₃)₃·6H₂O, in the presence of N(C₂H₅)₃. They all contain a crown-like [Mn₄Ln(μ-NO)₄]¹¹⁺ core with four Mn^III atoms being at the rim of the crown and an Ln^III ion occupying the dome of the crown. The peripheral ligation about the core is provided by four η¹:η¹:µ acetate groups. The identity of the Ln^III ions slightly affects the 12-metallacrown-4 frameworks, as demonstrated by the gradual decrease of the distances between the Ln^III ions and the centres of the Mn₄ planes (1.85 Å for 1, 1.81 Å for 2, 1.80 Å for 3, and 1.77 Å for 4). Variable-temperature dc magnetic susceptibility studies were carried out on polycrystalline samples of 1–4. Antiferromagnetic interactions are determined for complexes 1–4.     

Preparation,characterization and properties of fiber reinforced composites using silicon‐containing hybrid polymers

A novel glass fiber reinforced composite was prepared by using silicon‐containing hybrid polymers, poly(methylhydrogen‐diethynylsilyene) (PMES) and poly(phenylethynyl‐silyloxide‐phenylborane) (APABS), as matrix resins. The curing behavior and rheological properties of the matrix resins were investigated by differential scanning calorimetry (DSC) and rotational rheometer. The dynamic viscoelastic properties, mechanical properties, and microstructures of the composites were studied by dynamic mechanical analysis (DMA), universal testing machine (UTM), and scanning electron microscopy (SEM), respectively. The results show that the composite can be well cured between 200 and 300 °C through reactive groups like Si‐H, N‐H, and C≡C units, the possible thermosetting mechanism is also proposed. The composites exhibit excellent mechanical properties with bending strength reach up to 261 and 178 MPa before and after heat‐treating, respectively. SEM analysis clearly indicates that crack in the matrix, matrix/fiber interface debonding, and fiber pull out are predominate failure mechanism for the composites which are heat‐treated in different temperatures. All these obtained results can give theoretical guiding reference for their further applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and characterization of anion‐exchange membranes derived from poly(vinylbenzyl chloride‐co‐styrene) and intercalated montmorillonite

In this paper, three organic intercalating agents containing cations [hexadecyl trimethyl ammonium bromide (CTAB), poly(acrylamide‐co‐diallyldimethylammonium chloride), and quaternized polyethyleneimine] are used to prepare intercalated montmorillonites (MMT) by ion‐exchange method. Then the modified MMTs are doped with vinylbenzyl chloride and styrene copolymer [poly(vinylbenzyl chloride‐co‐styrene)] for fabricating composite anion‐exchange membranes (AEM). Fourier transform infrared, X‐raydiffraction, thermogravimetric analysis, scanning electron microscopy, and Mastersizer laser particle size analyzer are employed to characterize the structure and morphology of MMTs and AEMs. The successful intercalation of MMTs is approved, and the MMT intercalated by CTAB shows an interlayer distance of 2.31 nm. The properties of the composite membranes including water uptake, mechanical property, and ionic conductivity are investigated. Among all the AEMs, the composite membrane containing MMT sheets with CTAB demonstrates better compositive performances. It presents an ionic conductivity of 2.09 × 10^?2 S cm^?1 at 80°C and good alkaline solution stability. Copyright © 2016 John Wiley & Sons, Ltd.     

Gradient polymer networks formed by photopolymerization with self‐floating polysiloxane‐containing nanogel

Polysiloxane‐containing nanogels can be used as a fast, convenient and environmentally friendly method to control gradient photopolymerization and to obtain gradient polymer network because of its self‐floating feature. The chain length of polysiloxane is a key factor that influences the self‐floating capability of the polysiloxane‐containing nanogel. This paper reports a series of nanogels compositions synthesized with methacrylate‐modified polysiloxanes with different chain lengths, urethane dimethacrylate (UDMA) and isobornyl methacrylate (IBMA) at a molar ratio of 10:20:70 in the presence of a thiol chain transfer agent. The effect of polysiloxane chain length on self‐floating capability of the nanogel and gradient polymer network was researched. The results show that polysiloxane chain length is the main driving force for the self‐floating capability of the nanogels. The nanogel with long polysiloxane chain length exhibits good self‐floating capability in the monomer–polymer matrix because of the lower surface tension of polysiloxane. Furthermore, the gradient polymer network containing the nanogel with long polysiloxane chain length presents lower dispersion surface energy and greater hardness and thermostability. Copyright © 2016 John Wiley & Sons, Ltd.     

A novel method to prepare microcellular poly(vinyl alcohol) foam based on thermal processing and supercritical fluid

Combining the thermal processing and supercritical fluid technology develops a novel preparation method of microcellular poly(vinyl alcohol) (PVA). Water, as the plasticizer in system, can form the hydrogen bonding with pendant hydroxyl of PVA and weaken its strong intermolecular and intramolecular forces to realize the thermal processing. Supercritical carbon dioxide (sc‐CO₂) can easily dissolve into water‐plasticized PVA (WPVA) because of the destruction of crystal region caused by water, and the enhanced sc‐CO₂ solubility can greatly improve the foamability of WPVA. The porous structure generates through the saturation of sc‐CO₂ in WPVA sample and followed by pressure drop‐induced phase separation. The foaming behavior of WPVA was studied as a function of saturation pressure, foaming temperature, and saturation time. The cell density, cell size, and distribution of the obtained foam can be controlled by tuning processing conditions. The results revealed that the cell size decreased, and its distribution narrowed with saturation pressure increasing, or decrease of foaming temperature. But excessively increasing the saturation time generated a negative effect on the foaming behavior owing to the deteriorated plasticization effect resulted from the loss of water. Copyright © 2016 John Wiley & Sons, Ltd.     

A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High-Energy Sodium-Ion Batteries

Although sodium-ion batteries (SIBs) are considered as alternatives to lithium-ion batteries (LIBs), the electrochemical performances, in particular the energy density, are much lower than LIBs. A metal–organic compound, cuprous 7,7,8,8-tetracyanoquinodimethane (CuTCNQ), is presented as a new kind of cathode material for SIBs. It consists of both cationic (Cu^II↔Cu^I) and anionic (TCNQ⁰↔TCNQ⁻↔ TCNQ²⁻) reversible redox reactions, delivering a discharge capacity as high as 255 mAh g⁻¹ at a current density of 20 mA g⁻¹. The synergistic effect of both redox-active metal cations and organic anions brings an electrochemical transfer of multiple electrons. The transformation of cupric ions to cuprous ions occurs at near 3.80 V vs. Na⁺/Na, while the full reduction of TCNQ⁰ to TCNQ⁻ happens at 3.00–3.30 V. The remarkably high voltage is attributed to the strong inductive effect of the four cyano groups.     

Structural requirement of C11b chirality of tetrabenazine analogs as VMAT2 imaging ligands: synthesis and in vivo evaluation

We studied on the structural requirement of C11b chirality of tetrabenazine (TBZ) analogs as vesicular monoamine transporter 2 (VMAT2) ligands. TBZ analogs (2, 6a, 6b) and ¹⁸F-radiolabeled [¹⁸F]6a and [¹⁸F]6b with eliminated C11b chirality were synthesized and characterized. Competition studies demonstrated that 2, 6a and 6b displayed much lower in vivo VMAT2 bindings than TBZ. MicroPET imaging studies of [¹⁸F]6a and [¹⁸F]6b showed negligible accumulation in VMAT2-enriched regions as compared with the known VMAT2 ligand ¹⁸F-FP-(+)-DTBZ. These results suggest that C11b chirality of TBZ analogs is essential for in vivo VMAT2 binding bioactivity.     

聚脲多孔材料的简单制备及在酶固定和手性拆分中的应用

以甲苯二异氰酸酯(TDI)为单体,在水与丙酮混合溶剂中通过沉淀聚合一步法制备了富含胺基的聚脲多孔材料(PPU),通过扫描电镜和压汞法对其表面形貌和孔结构进行了表征.PPU经戊二醛(GA)活化后用于荧光假单胞菌脂肪酶(PFL)的固定,考察了GA活化过程中GA浓度对酶固定量及固定酶活性的影响.结果表明,PPU是一种粒子尺寸分布在30~50μm范围的形状不规则的多孔粒子,孔径在2 nm~100μm之间呈连续分布.在pH=8.0的缓冲溶液中用0.17 mol/L的GA对PPU进行改性,将改性后的PPU用于PFL的固定,当酶溶液浓度为2.56 mg/m L时,得到酶的最大固定量为95.2 mg/g,固定酶的活性为375 U/mg,相对活性为76%.将此固定酶作为催化剂,用于1-苯乙醇外消旋化合物的手性拆分,并与游离酶催化的结果相比较.结果表明,固定酶的反应活性和立体选择性都明显优于游离酶.通过沉淀聚合制备的聚脲多孔材料在酶固定及手性分子拆分方面具有应用前景.