Nanoalloy Based on Clays: Intercalated‐Exfoliated Layered Silicate in High Performance Elastomer

A novel method is described for the preparation of nanocomposites comprising a high performance rubber for tire application and layered silicates clay. In this work nanocomposites of solution‐styrene butadiene rubber (S‐SBR) with montmorillonite layered silicate were prepared with carboxylated nitrile rubber (XNBR), a polar rubber, as a compatibilizer. A sufficient amount of organomodified layered silicate was loaded in carboxylated nitrile rubber (XNBR) and this compound was blended as a master batch in the S‐SBR. Mixed intercalated/exfoliated morphologies in the nanocomposite are evinced by X‐ray diffraction measurements and transmission electron microscopy. Dynamic mechanical analysis also supports the compatibility of the composites. A good dispersion of the layered silicate in the S‐SBR matrix was reflected from the physical properties of the nanocomposites, especially in terms of tensile strength and high elongation properties.     

Synthesis of Low Molecular Distribution Dihydric Polybutadiene in the Presence of Triflic Acid

A method is described for the preparation of functional polybutadiene (PB) with hydroxyl groups along the polymer chain. This material can be used directly or as the starting substrate for further polymerization in both academic and industrial processes. We have developed a convenient method to obtain a polymer with a narrow molecular weight distribution and with a known content of hydroxyl groups along the backbone. By controlling the hydroxylation reaction conditions, the appropriate molar ratios of THF, water and acid with the epoxide are 30, 15 and 1.5, respectively. By minimizing the crosslinking reaction, the desired PB was prepared and subsequently characterized.     

Synthesis of a Dithiocarbamate Chelate Resin and Its Oxidized form and Their Adsorption Properties for Heavy Metal Ions

A series of macroporous dithiocarbamate chelate resins, III and V, and an oxidized resin, VI, with high adsorption capacity were prepared. The influence of various reaction conditions of amination, dithiocarboxylation, and oxidation were examined. The structure and the conversion of functional groups of resins were confirmed by IR spectra and elemental analysis. The adsorption capacities of Resin II for Hg²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ are 4.40, 2.44, 1.77, and 1.36 mmol/g, respectively. The adsorption capacities of Resins V and VI for Cu²⁺. Zn²⁺, Ni²⁺, Co³⁺, Ag⁺, Hg²⁺, Cd²⁺, Pb²⁺, and Au³⁺ are 4.07–0.51 and 3.81–0.59 meq ion/g, respectively. The adsorption rate and the influence of pH on the adsorption percentage of the resins for metal ions were examined. Noble metal, transitional metal, and heavy metal ions can be quantitatively adsorbed by the resins. The adsorbed Cu²⁺, Pb²⁺, Cd²⁺, Co³⁺, and Ni²⁺ can be quantitatively eluted with 5N HNO₃, and the presence of large amounts of Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺ did not interfere.     

Effect of the self-assembly of collagen on crystallisation of calcium carbonate in aqueous solution

In order to investigate how the self-assembly of organic matrix influences crystallisation and growth of inorganic minerals, we selected collagen as the matrix and conducted three experiments of crystallisation of CaCO₃ in different reaction systems: H₂O system, as-assembled collagen fibrils system and self-assembling of collagen system. It is found that (i) the self-assembly process of organic matrix had a remarkable effect on the morphology of inorganic minerals: CaCO₃ crystals formed in the as-assembled collagen fibrils system were global clusters and those formed in the self-assembling of collagen system appeared as interlaced networks and (ii) the organic matrix decided the polymorph of crystals: CaCO₃ crystals were calcite in the H₂O system and appeared vaterite in the collagen system. From this study, we can conclude that the self-assembly of collagen fibrils greatly affect the crystallisation and growth of CaCO₃. Such results are significant in understanding the mechanism of biomineralisation in calcified tissues in general, and useful in the synthesis of biominerals.

(a)?CaCO₃ formed in the as-assembled collagen fibrils system. (b)?CaCO₃ formed in the self-assembling of collagen monomer system.The TEM images of samples obtained in the as-assembled collagen fibrils and self-assembling of collagen monomer system, were observed, respectively. The result shows that crystals CaCO₃ formed in the as-assembled collagen fibrils system were global clusters; crystals CaCO₃ formed in the self-assembling of collagen monomer system appeared interlaced networks.     

Improved molten salt synthesis and structure evolution upon cycling of 0.5Li2MnO3·0.5LiCoO2 in lithium-ion batteries

The Li-rich cathode material Li_1.2Co_0.4Mn_0.4O₂(=0.5Li₂MnO₃·0.5LiCoO₂) was prepared by an improved molten salt method. The effects of sintering temperature and time on the physical and electrochemical properties of Li_1.2Co_0.4Mn_0.4O₂ were investigated. With increasing sintering temperature, excellent crystallinity and a stable structure are obtained, which lead to excellent electrochemical properties. However, the sample sintered at 900 °C has poor performance because its large powder diameter prolongs the transportation length of Li⁺ ions. Higher specific surface areas are obtained when samples are sintered at 850 °C for a shorter time, which leads to more activity and excellent charge/discharge capacity. The evolution of a derivative peak at about 3.0 V in the differential capacity (dQ/dV) curves is observed along with the formation of a spinel-like phase, which is verified by analysis using a high-resolution transmission electron microscope. Therefore, it is a simple and quick method to characterize the structure evolution upon cycling of Li-rich cathode materials by means of analysis of the derivative peak.     

IPET:测定独个生物大分子三维空间结构的实验方法

蛋白质的动态特性和结构活性对于蛋白质功能的调控具有根本意义。传统的结构确定方法(包括X射线和电子显微镜单颗粒分析技术等)往往需要成千上万不同蛋白质分子的平均信号,因此难以确定蛋白质分子的动态结构。而电子显微断层成像技术是一种对独个生物个体结构从不同的观测角度照相、并计算来恢复该个体的三维结构密度图的方法。传统的冷冻电子断层成像重构方法采用整个大尺寸电镜图像进行重构计算,通常用来研究细菌、细胞切片等大尺寸生物个体在较低分辨率下的结构;由于分辨率的限制,不足以获得小尺寸的蛋白质分子的结构细节。最近,任罡研究小组提出一种独个生物颗粒的电子显微断层成像方法(individual-particle electron tomography,IPET)。该方法通过减小图像尺寸(直至所选区域只包含单个蛋白质分子)的策略,运用提出的FETR(focused electron tomography reconstruction)算法来提高独个大分子重构的分辨率。此方法不需要初始模型和大量分子的平均信号,同时能够容忍一定的测角误差。本文综述了IPET/FETR方法在确定独个分子结构过程中的具体步骤以及如何应用该方法来研究蛋白动态特性和结构变化特征。期望通过该综述和国内同行交流,分享最新的前沿研究,为赶超世界科技前沿的建设添砖加瓦。     

Two Bisupporting Keggin-Type POM-Based Hybrids Decorated by [Zn(phen)2]2+ Fragments

Two bisupporting Keggin-type polyoxoanion-based hybrids decorated by [Zn(phen)₂]²⁺ complexes, [Zn(phen)₂]₂(PW ₁₁ ^VI W^VO₄₀) (1) and K[Zn(phen)₂(H₂O)]₂(OH) (SiW₁₂O₄₀)·H₂O (2) (phen = 1,10′-phenanthroline), have been hydrothermally synthesized, and characterized by elemental analysis, IR spectra, UV–Vis spectrum, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, and single-crystal X-ray diffraction. The structural analyses reveal that compound 1 consists of a 0D bisupporting Keggin-type heteropoly blue cluster obtained by using reductant glucose, which is grafted by two [Zn(phen)₂]²⁺ fragments; compound 2 presents a 1D infinite chain, which is constructed from bisupporting [SiW₁₂O₄₀]^4? polyoxoanions decorated by [Zn(phen)₂(H₂O)]²⁺ fragments and K⁺ ions. Additionally, the electrochemical behaviors of two compounds were studied.     

The non-covalent bindings of CF2Cl2 with NO and SO2

Ab initio calculations have been performed on the complexes of CF₂Cl₂ with NO and SO₂, and a set of stable configurations for CF₂Cl₂–NO and CF₂Cl₂–SO₂ were found with no imaginary frequencies by the MP2 method. In addition, the binding energy and the NBO analysis were used to evaluate the relative stability of the complexes. The calculated results indicate that the weak interactions in the CF₂Cl₂–NO and CF₂Cl₂–SO₂ systems involved are enhanced with the increase of the number of non-covalent bonds. Further studies predict that the CF₂Cl₂–SO₂ system may play a more important role than the CF₂Cl₂–NO system in environmental problem because the former offers a stronger interaction than the latter. Furthermore, the non-covalent binding interactions of Cl···N and Cl···O for CF₂Cl₂–NO system, Cl···O, Cl···S and F···S for CF₂Cl₂–SO₂ system, are the dominant forces, which seem to be very significant as a driving force influencing the arrangement of molecules, especially in CF₂Cl₂–SO₂ system.