Toward the Rational Design of Conjugated Oligomers and Polymers: Systematic Study of the Substituent Effect in Oligothiophenes

A systematic study of substituent electronic effects on a number of oligothiophene properties was performed using well-defined oligothiophenes of various chain lengths that were monosubstituted with classical electron-withdrawing or -donating groups. The main focus was to understand how the effect of a substituent on one thiophene ring was transmitted through the other thiophene rings in the oligomer. The physical and electrochemical properties were studied by optical absorption and emission spectroscopy and by cyclic voltammetry. The experimental data were complemented with theoretical calculations of HOMO LUMO gaps, charge distribution, bond length alternations, and ¹³C NMR spectra. We show that substitution has a significant electronic effect on the substituted ring; however, the effect decreases strongly over conjugation. A semiquantitative evaluation of the substituent effect in a well-defined long conjugated system was obtained for the first time using the Hammett equation.     

Raman Spectroscopic Characterization of Polyselenophenes and Poly(3,4-ethylenenedioxyselenophene)s

Herein we present novel Raman spectroscopic studies carried out for polyselenophene ( PSe ), poly(3,4-ethylenedioxyselenophene) ( PEDOS ), and alkyl-substituted poly(alkyl-3,4-ethylenedioxyselenophene) ( PEDOS - Cn : n=2, 8, and 12) homologues. These spectroscopic data are combined with morphological and structural analysis techniques, such as AFM, and DFT simulations. An investigation into the extent of π-conjugation in PSe is presented by comparing its spectral signatures with those of a homologous series of oligoselenophenes. Our experimental data suggest that π-conjugation in the PSe backbone extends to more than six selenophene units. The incorporation of ethylenedioxy (EDO) groups in PEDOS results in a more complex spectrum and a downshift of the CC/C C stretching vibration (or effective conjugation coordinate (ECC) mode); this provides evidence for an improvement in the π-conjugational properties along the PSe backbone upon EDO substitution. The dispersity of π-conjugation lengths in different PEDOS samples obtained through different synthetic routes is evaluated as a function of different structural factors. Finally, we present experimental evidence that the insertion of alkyl chains into the EDO units slightly impacts on the π-conjugational properties of the PEDOS backbone in the non-annealed samples (with an improved π-electron delocalization found in PEDOS - C8 ), but moderately affects the degree of molecular order of polymer films upon thermal annealing.     

偶联剂对nano-ZnO/HDPE复合材料性能的影响

通过熔融共混法制备出不同硅烷偶联剂(KH550,KH560)改性的nano-ZnO/HDPE复合材料,并考察了偶联剂及ZnO含量对复合材料性能的影响。结果表明:改性nano-ZnO对HDPE基体起到了明显的增强增韧的效果,当改性nano-ZnO含量为0.2%～0.5%时,复合材料的力学性能最好。此外,nano-ZnO在HDPE中起异相成核剂的作用,从而使体系的熔融温度、结晶温度和结晶度升高。经KH560处理的nano-ZnO/HDPE复合材料的力学性能和结晶性能均优于经KH550处理的nano-ZnO/HDPE复合材料的性能。     

FCC汽油降烯烃工艺及催化剂研究进展

针对国VI汽油标准大幅度降烯烃的需要及乙醇汽油对有机含氧化合物含量的严格要求,从分子炼油角度出发,按照烯烃碳数C_4、C_5～C_6、C_5～C_8的顺序分别介绍并分析催化裂化(FCC)汽油降烯烃后处理技术,包括MTBE生产、烷基化、醚化、异构化/芳构化工艺发展状况、优缺点与应用局限。由于乙醇汽油的推广,MTBE生产技术与轻汽油醚化技术将面临停产的困境与改造的挑战,而烷基化、异构化/芳构化等生产高辛烷值汽油组分的技术是更具潜力的FCC汽油降烯烃技术,将得到大力发展。此外,总结常用工业催化剂及其改性研究,并简述存在问题与发展方向,提出汽油组分比例优化、MTBE装置改造等建议与展望,为FCC汽油降烯烃工艺技术路线选择提供借鉴。     

催化裂化汽油砷化物分布规律

采用自动快速蒸馏装置对脱砷前后的催化裂化汽油进行窄馏分切割,利用原子荧光光谱法对各窄馏分砷化物含量进行分析,研究催化汽油脱砷前后砷化物分布规律,为催化裂化汽油脱砷剂开发及脱砷工艺流程选择提供指导。实验结果表明：随着各窄馏分沸点增加,砷化物所占比例逐渐增大,90%以上砷化物均分布在80℃以上的重汽油组分中,尤其170℃以上馏分砷化物所占比例陡增,占总砷化物65.82%~96.31%。吸附脱砷剂对汽油150℃之前馏分中砷化物实现了全部脱除,而对150℃之后的重馏分脱砷率略有下降;临氢脱砷剂对汽油中80℃之前轻馏分和170℃之后重馏分中砷化物具有较高的脱除率,达到90%以上,而对中间馏分中砷化物脱除率较低。     

3-Aminopropyltriethoxysilane-Assisted Si@SiO2/CNTs Hybrid Microspheres as Superior Anode Materials for Li-ion Batteries

A silicon based composite (Si@SiO₂/CNTs) with outstanding electrochemistry performance has been easily synthesized using a spray drying method; The composite microsphere is mainly made up of carbon nanotubes and the prepared nano silicon particles. With the help of a silane coupling agent, carbon nanotubes tightly intertwined with nano silicon particles and formed microspheres together. On the surface of the prepared nano silicon particles, a layer of oxide film plays a role as a barrier to reduce the rupture of the particles during the lithium intercalation/extraction process. In addition, the added twisted carbon nanotubes can help to maintain the conductive network, thus stabilizing the electrode working environment during the lithium intercalation/extraction process. As a superior anode material, an initial specific discharge capacity of approximately 2846.9 mAh g^?1 with a coulombic efficiency of 86 % and a reversible specific capacity of 2035.9 mAh g^?1 after 100 cycles at a constant density of 500 mA g^?1 are obtained.     

Mechanism of BRAF Activation through Biochemical Characterization of the Recombinant Full‐Length Protein

BRAF kinase plays an important role in mitogen‐activated protein kinase (MAPK) signaling and harbors activating mutations in about half of melanomas and in a smaller percentage in many other cancers. Despite its importance, few in vitro studies have been performed to characterize the biochemical properties of full‐length BRAF. Herein, a strategy to generate an active, intact form of BRAF protein suitable for in vitro enzyme kinetics is described. It is shown that purified, intact BRAF protein autophosphorylates the kinase activation loop and this can be enhanced by binding the MEK protein substrate through an allosteric mechanism. These studies provide in vitro evidence that BRAF selectively binds to active RAS and that the BRAF/CRAF heterodimer is the most active form, relative to their respective homodimers. Full‐length BRAF analysis with small‐molecule BRAF inhibitors shows that two drugs, dabrafenib and vemurafenib, can modestly enhance kinase activity of BRAF at low concentration. Taken together, this characterization of intact BRAF contributes to a framework for understanding its role in cell signaling.     

RuO_ 2/MO_x-TiO_2(M=Ce、Mn、La、Zr、Co)催化剂制备及其氯化氢氧化性能

氯化氢催化氧化制氯气具有高效率、低能耗、环境友好等优点,一直是研究的热点。首先采用浸渍法制备RuO_2/TiO_2催化剂,并通过催化活性评价和H_2-TPR表征优化Ru的负载量。然后制备Ce、Mn、La、Zr、Co等氧化物修饰的MO_x-TiO_2(M=Ce、Mn、La、Zr、Co)载体及RuO_2/MOxTiO_2催化剂,考察不同修饰物对催化剂氯化氢氧化性能的影响。结果表明,采用该型号TiO_2载体时最佳负载质量分数为2%~3%;MO_x-TiO_2载体中MOx修饰物均呈高分散状态,La、Zr、Ce等氧化物修饰后,TiO_2晶粒尺寸增大,其中Zr、Mn、Co等氧化物掺杂进入TiO_2晶格。Ce和Zr氧化物修饰可以提高RuO_2/TiO_2催化剂催化活性,Mn、Co、La等氧化物修饰对活性有不利影响。Mn、Co氧化物修饰可以降低反应活化能,所以这两种氧化物修饰的催化剂催化活性较低是由指前因子减小导致的,这意味着进一步提高RuO_2/MO_x-TiO_2(M=Mn、Co)催化剂活性组分分散性才能开发出活性更好的催化剂。     

Novel allene oxide synthase products formed via Favorskii-type rearrangement: mechanistic implications for 12-oxo-10,15-phytodienoic acid biosynthesis

The allene oxide synthase (AOS) pathway is widespread in plants. Its products, such as cyclopentenone 12-oxo-10,15-phytodienoic acid (12-oxo-PDA) and related jasmonates, play important biological roles in plants. We found that 12-oxo-PDA in some plant tissues co-occur with an unknown minor oxylipin 1. In vitro incubations of AOSs with α-linolenic acid 13(S)-hydroperoxide reliably afforded 1 along with 12-oxo-PDA and α-ketol. A similar oxylipin 3 was formed during the AOS conversions of γ-linolenic acid 9(S)-hydroperoxide. Linoleic acid hydroperoxides formed neither products similar to 1 and 3 nor cyclopentenones. Oxylipins 1 and 3 were purified and identified as the products of Favorskii-type rearrangement, (2'Z,4Z)-2-(2'-pentenyl)-4-tridecene-1,13-dioic acid and (2'Z,4Z)-2-(2'-octenyl)-4-decene-1,10-dioic acid, respectively. Detection of Favorskii products 1 and 3 demonstrates that cyclopropanones are short-lived AOS products along with allene oxides. The observed parallels between the Favorskii product 1 and 12-oxo-PDA formation suggests that cyclopropanone is either a byproduct or a precursor of 12-oxo-PDA.     

橡胶机械产品用轧辊在机械加工中易出现问题分析

本文首先从轧辊在产品中的功用、结构形式、特点,以及轧辊机械加工主要工艺流程入手,对轧辊在机械加工中易出现的问题进行了分析,并论述了应采取的相应措施。