Freestanding graphitic carbon nitride-based carbon nanotubes hybrid membrane as electrode for lithium/polysulfides batteries

Lithium sulfur batteries have drawled worldwide attention in recent years, which benefit of its high-density energetic, low cost, and environmental benignity. Nevertheless, the shuttle effect of polysulfides and resulting self-discharge lead to capacity fade loss and poor electrochemical performance. Herein, graphitic-carbon nitride/carbon nanotubes (g-C₃N₄/CNTs) hybrid membrane is fabricated by the flow-direct vacuum filtration process. The as-prepared 3-D freestanding g-C₃N₄/CNTs membrane employed as positive current collector containing Li₂S₆ catholyte solution for lithium/polysulfides batteries. The fabricated g-C₃N₄/CNTs provide a physical barriers and chemisorption resist polysulfide shuttling. Moreover, the conductive network constructed by CNTs can empower sulfur to be evenly distributed in the cathode and accelerates electron transport. Thus, to further prove the cooperative effect of g-C₃N₄ and CNTs, the freestanding g-C₃N₄/CNTs/Li₂S₆ electrode exhibits more stable electrochemical performance than CNTs/Li₂S₆ electrode, deliver the first discharge capacity of 876 mAh g⁻¹ at 0.5 C and maintained at 633 mAh g⁻¹ after 300 cycles. The sulfur mass in electrode was increased to 7.11 mg, and the g-C₃N₄/CNTs/Li₂S₆ electrode also possess a high capacity retention of 75.5%. Meanwhile, g-C₃N₄ modified CNTs can not only trap polysulfides by strong adsorption but also effectively inhibit the self-discharge behavior of lithium/polysulfides batteries. As a consequence, the g-C₃N₄/CNTs composites for lithium/polysulfides batteries are indicating an excellent electrochemical stability with a long-term storage without obvious capacity degradation.     

Macrocyclization of Organo‐Peptide Hybrids through a Dual Bio‐orthogonal Ligation: Insights from Structure–Reactivity Studies

Macrocycles constitute an attractive structural class of molecules for targeting biomolecular interfaces with high affinity and specificity. Here, we report systematic studies aimed at exploring the scope and mechanism of a novel chemo‐biosynthetic strategy for generating macrocyclic organo‐peptide hybrids (MOrPHs) through a dual oxime‐/intein‐mediated ligation reaction between a recombinant precursor protein and bifunctional, oxyamino/1,3‐amino‐thiol compounds. An efficient synthetic route was developed to access structurally different synthetic precursors incorporating a 2‐amino‐ mercaptomethyl‐aryl (AMA) moiety previously found to be important for macrocyclization. With these compounds, the impact of the synthetic precursor scaffold and of designed mutations within the genetically encoded precursor peptide sequence on macrocyclization efficiency was investigated. Importantly, the desired MOrPHs were obtained as the only product from all the different synthetic precursors probed in this study and across peptide sequences comprising four to 15 amino acids. Systematic mutagenesis of the “i?1” site at the junction between the target peptide sequence and the intein moiety revealed that the majority of the 20 amino acids are compatible with MOrPH formation; this enables the identification of the most and the least favorable residues for this critical position. Furthermore, interesting trends with respect to the positional effect of conformationally constrained (Pro) and flexible (Gly) residues on the reactivity of randomized hexamer peptide sequences were observed. Finally, mechanistic investigations enabled the relative contributions of the two distinct pathways (side‐chain→C‐end ligation versus C‐end→side‐chain ligation) to the macrocyclization process to be dissected. Altogether, these studies demonstrate the versatility and robustness of the methodology to enable the synthesis and diversification of a new class of organo‐peptide macrocycles and provide valuable structure–reactivity insights to inform the construction of macrocycle libraries through this chemo‐biosynthetic strategy.     

有机过渡金属络合物均相催化发展及展望

介绍了国内外均相络合催化的研究及发展，并对均相络合催化的发展方向进行了展望。     

Preparation and characterization of composite membranes of polysulfone and microcrystalline cellulose

Physical and chemical modifications of polymeric ultrafiltration membranes are necessary to improve their hydrophilic properties, strength, and other characteristics. Microcrystalline cellulose (MCC) was prepared from cellulose pulp by acid‐catalyzed hydrolysis in the presence of ultrasonic radiation, and the properties of MCC were evaluated. Through the addition of MCC to a polysulfone (PS) membrane solution, a casting solution of a PS/MCC blend was obtained. Subsequently, the ultrafiltration membrane from the blend was further developed in a phase‐inversion process comprising immersion and deposition. The capacity for ultrafiltration was better with increasing MCC content. When the ratio of MCC to PS was 0.3, the pure water flux of the composite membrane reached 234.2 L/m²/h, and the retention of a bovine serum albumin solution (1 g/L) was as high as 93.4%. The membranes were also observed with scanning electron microscopy and atomic force microscopy to study their microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Retracted: Mechanical and thermal properties enhancement of polycarbonate nanocomposites prepared by melt compounding

The following article from the Journal of Applied Polymer Science, “Mechanical and thermal properties enhancement of polycarbonate nanocomposites prepared by melt compounding” by Sanjay K. Nayak, Smita Mohanty, and Sushanta K. Samal, published online on 7 April 2010 in Wiley Online Library (J. Appl. Polym. Sci. 2010 , 117, 2101; http://onlinelibrary.wiley.com/doi/10.1002/app.31222/full ), has been retracted by agreement between the authors, the journal's editors, and Wiley Periodicals, Inc. The retraction has been agreed due to significant overlap with respect to another article, “Effect of hydrogen bonding on the rheology of polycarbonate/organoclay nanocomposites,” by Kyung Min Lee, and Chang Dae Han, published online on 19 June 2003 in Polymer ( 2003 , 44, 4573).     

EP树脂/Mt纳米复合材料的制备与性能研究

以双酚Ａ型环氧（ＥＰ０树脂为基体,有机胺处理蒙脱土（Ｍｔ）为增强剂,制备了ＥＰ树脂／Ｍｔ纳米复合材料。通过热重分析、Ｘ射线衍射、透射电子显微镜等方法对纳米复合材料的制备条件进行了优化,对聚合物基纳米复合材料的结构、力学性能、热性能进行了表征。     

Transport and solubility of fluids into polyphenylene sulfide (PPS)

The solubility and transport of toluene and carbon disulfide into amorphous and crystalline polyphenylene sulfide (PPS) was investigated. The rates of sorption, desorption, and resorption of both fluids were measured as a function of temperature. The sorption of these fluids into amorphous PPS produces a semi‐crystalline material by solvent induced crystallinity (SIC). Although the rate of diffusion of carbon disulfide (CS₂) into crystalline PPS, (produced either thermally or by SIC), is several orders of magnitude slower than that observed in amorphous PPS, the solubility is only slightly reduced, by approximately 10%. The PPS films exhibit highly stressed surface regions that rapidly sorb the penetrant. Thermal annealing at temperatures as high as 100°C (note T_g of PPS is 85°C) has little or no effect on the surface stress, the diffusion process or the solubility of toluene into PPS. In addition to SIC, PPS undergoes cold crystallization at 130°–140°C; however, the degree of crystallinity induced by cold crystallization is approximately 60% of that formed by cooling from the melt. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 615–625, 2003     

有机硅改性无皂丙烯酸酯类水分散体的合成技术及其产业化实践

介绍了以特殊结构的纳米无机体材料为骨架,采用无皂工艺合成的以有机硅材料进行改性的具有LIPN结构的丙烯酸酯类水分散体的性能及其产业化实践的情况,并对以该水分散体开发的水性木器涂料的性能作了对比说明。实践表明,以该丙烯酸水分散体开发的水性木器涂料较好地解决了目前水性木器涂料在硬度、光泽度、丰满度、回粘温度等方面不如溶剂型涂料的弱点,且该分散体的合成工艺独特、成本低廉,利于产业化和下游厂家开发使用。