Polyolefins: The most promising large-volume materials for the 21st century

Polyolefins (POs) constitute an extremely interesting family of materials. They include large-volume materials such as polyethylene and polypropylene and specialty materials. Outstanding scientific and technology developments have led to the most aggressive, endless, always increasing, successful growth speed of any family of large-volume materials. For those of us who have lived through the entire PO adventure, from its problematic beginnings to the eventual successful developments of the last 25 years, it has been a quite unforeseeable and unexpected story not shared by the majority. The main reason for such behavior and the present situation is the inherent complexity of their catalytic systems, which are difficult to understand and manage, along with all the consequences in terms of the process versatility, the reliability and cost, the lack of product properties, and the possibility of new material creation and commercial availability. After the early commercial disappointments of the 1960s and early 1970s, the deep commitment of the industry in research and development, mostly aimed at an understanding of the catalysis and its improvement and management, created the basis for and led to the generation of new, elegant, and versatile processes and, most importantly, to the generation of new products and properties. It activated that dynamic and aggressive growth that, since the late 1970s, has characterized the entire PO market and still, at the beginning of the third millennium, is not showing any sign of decline. An attempt to provide a rational explanation for such a unique case of technological and commercial success in the history of materials has led us to the following conclusions. First, dramatic improvements in the polymer properties and the generation of new materials have been the key reasons for their commercial success and continuous market expansion. Second, the tremendous and dynamic development of new, elegant, and versatile technologies has been and is the fundamental prerequisite for the generation of that rich world of new properties and materials. Third, the strategic management of the technological background and potential for the creation of new properties and new applications has been and is the basis for the fast and successful market expansion. The key technological driving force has been the understanding and management of the catalytic system. The early generations of chromium-based and Ziegler–Natta catalysts, after a difficult beginning, have progressively accelerated in their development toward new revolutionary generations with outstanding potential in terms of the creation of new polymer properties. The most recent families of single-site catalysts, together with the still largely unexploited potential of the previous Ziegler–Natta, chromium, and vanadium catalysts, are showing the ability to guarantee the continued support and fueling of the expansion for several further decades. The development philosophy will always be more tuned toward the creation of low-cost, low-environmental-impact polymers and processes, with a minimum amount of constraints. Today, at the beginning of the new century, we see the PO future as still very bright because of the huge, unexploited potential of already existing and emerging technologies. The PO adventure continues and is still exciting like it was 50 years ago. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 396–415, 2004     

Study of complex mixtures of natural substances by the defocusing and dadi methods. VI. Components of the secretion of the pre-anal gland of some poisonous snakes

By mass-spectrometric methods, cholesterol and docosanoic, heneicosanoic, cicosanoic, octadecanoic, cis-octadec-9-enoic, heptadecanoic, hexadecanoic, and pentadecanoic acids have been identified in the odoriferous secretion of the pre-anal glands of the females and males of the common adder and the saw-scaled viper and in those of females of the common mamushi. It has been established that the chemical compositions of the secretions of these glands of the females of the adder, the viper, and the mamushi and of the males of the adder and of the viper are not identical.     

Liquid-phase oxidation of dibenzyl ether by atmospheric oxygen in the presence of homo- and heteroligand pivalate and 3,5-dimethylpyrazolate complexes of 3<Emphasis Type="Italic">d</Emphasis> metals

The main products of the reaction in the presence of homo- and heteroligand pivalate and 3,5-dimethylpyrazolate mono-, bi-, and trinuclear complexes of Co, Cu, Ni, and Zn are the hydroperoxide, benzaldehyde, and benzoic acid. The effect of the composition and structure of the complexes on the conversion of the substrate, the selectivity of the process, and the possibility of alternative routes to the oxidation of dibenzyl ether is discussed.     

OPTICAL ROTATION STUDIES OF COPPER (II)-TRIPEPTIDE COMPLEXES

Abstract

Copper(II) complexes of various optically active di- and tripeptides have been studied with the aid of optical rotatory dispersion (ORD) and circular dichroism (CD) techniques. The magnitudes of the molecular rotations related to the d-d transitions of the complexes fall into three different ranges, depending on the positions of asymmetric carbon atoms of the ligands. The molecular rotations of GAG and GLG complexes are greater than those of GGA, GGL, and GGV complexes, which are again greater than those of AGG, LGG, and VGG complexes (G, A, L, and V are glycine, alanine, leucine, and valine residues, respectively, in the tripeptides investigated, the N-terminal residue being the first residue in each abbreviation). The structures of these complexes, deduced from their potentiometric equilibrium curves and from the known crystal structure of the copper(II)-triglycine complex, show that the asymmetric carbon atoms of the second and third amino acid residues (counting from the N-terminal amino acid residue) are in the plane composed of the central metal ion, the nitrogen atoms of the amino and peptide groups, and the oxygen atom of the carboxylate group. The magnitude of the Cotton effect increases with the planarity of the chelate rings which include the asymmetric carbon atom and the metal ion, and with increasing strength of the coordinate bonds that form these chelate rings. Further support for this interpretation is found in the CD spectra of the copper(II) and nickel(II) complexes of AGG, GAG, GGA, and AAA. Analysis of the CD spectra of LL and DL alanylalanine complexes also demonstrate the influence of planarity and coordinate bond strength on the magnitude of the Cotton effect. Schiff base formation of aldehydes and ketones with dialanines causes fundamental changes in the geometries of the copper(II) complexes and reverses the relative contributions of the chelate rings to the total CD absorption intensities of the complexes.     

Regularities in molecular properties of ground state stable diatomics

A simple relationship is reported between vibrational frequencies, bond lengths, and reduced masses for many families of stable, ground state diatomics: the frequency is proportional to the reciprocal of the product of the bond length and the square root of the reduced mass. This is demonstrated with each of the following related families: the alkali metal diatomics, the group 15 diatomics, the group 16 diatomics, the halogen diatomics, the alkali metal hydrides, the alkaline earth oxides, the group 14 oxides and their sulfides, the diatomics of carbon, of silicon and of germanium with group 16 elements, the hydrogen halides, the halides of lithium, of sodium, of potassium, of rubidium and of cesium, the chlorides of the alkali metals and of silver, and the polyatomic hydrides of groups 14 and 15. Although correlation coefficients of 0.99 or greater in each of the 21 families examined demonstrate the validity of the correlation, the deviations found are significantly larger than can be attributed to experimental uncertainties.     

Electrochemical and ESR-study of the mechanism of organic compound oxidation in the presence of mediators—Radical cations of substituted pyrazin-di-N-oxydes

The mechanism of methanol, ethanol, diethyl ether, triethyl-o-formate, cyclohexanol, and cyclohexane oxidation in the presence of electrochemically generated radical cations of 2,5-dimethyl-, 2,3,5,6-tetramethyl-, 2,3-dimethyl-5,6-cyclohexa-, and 3-phenyl-5,6-cyclohexapyrazin-di-N-oxydes as mediators was studied by cyclic voltammetry, ESR-electrolysis, and gas chromatography. The studies were carried out at glassy-carbon-, Pt-, and Au-electrodes in 0.1 M LiClO₄ solutions in acetonitrile and methanol, the alcohol being used as a solvent and substrate simultaneously. ESR-spectra of the radical cations of the pyrazin-di-N-oxydes were recorded. Effects of temperature, oxygen, admixtures of water and acid, and the nature of substrate and solvent on the shape of the cyclic voltammograms and intensity of the ESR-spectra of the pyrazin-di-N-oxydes are elucidated. By comparing experimental and calculated voltammograms, the rate constants for the interaction between the pyrazin-di-N-oxydes and the substrates C-H-bonds are determined. Mechanism of the ultimate two-electron catalytic oxidation of the organics as a constituent of complexes, formed with the radical cations of the mediators (pyrazin-di-N-oxydes), is suggested.     

纳米材料-蛋白质界面相互作用的分子机制

纳米材料由于其优异的性能在化工、电子、机械、环境、能源、航天等各个领域已经得到了广泛的应用,并且在生物医学方面的应用越来越受到重视。纳米材料-蛋白质界面相互作用是纳米生物医学领域重要的科学问题,对于纳米材料的生物医学应用以及生物安全性评价至关重要。蛋白质分子与纳米材料在界面的相互作用,一方面可以诱导蛋白质的构象、组装结构甚至功能的改变,另一方面可以引起纳米材料的表面亲疏水性、电荷性质等表面物理化学性质的改变。基于蛋白质与纳米材料相互作用检测技术及结果,本文从分子水平阐述了纳米材料与蛋白质分子在界面之间的相互作用机理及相应的结构与性质的变化,从而可以深化对两者之间复杂的相互作用机制的理解,对于推进纳米材料在生物医学的应用及健康、安全、持续发展具有重要意义。     

Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.     

超快扫描量热技术表征高分子结晶动力学

高分子结晶行为是高分子材料加工过程研究的热点,因为高分子组分和加工工艺控制着高分子结晶及其产物性能。差示扫描量热仪(DSC)是研究高分子结晶动力学常规手段。但是,普通DSC所能达到的最快降温速率一般无法抑制较快的样品结晶,结晶行为将在等温结晶动力学测试之前发生,因此可进行等温结晶的研究温度范围局限于较低结晶过冷度的高温区域。近年来,具有超快速升降温扫描速率和精准控温的快速扫描芯片量热仪(FSC,其商业化版本Flash DSC 1)得到了广泛应用。FSC可以抑制高分子样品在升降温过程中的结晶成核,避免对之后的结晶动力学测试产生影响。因此FSC技术将高分子结晶动力学的研究温度区间延伸至具有较大过冷度的低温区,加深了我们对高分子结晶成核机理以及高分子工业加工过程的理解。本文首先介绍了由初级成核方程描述的高分子结晶动力学原理,初级成核自由能位垒(?G~*)和扩散活化能位垒(?U)分别控制了高低温区的结晶动力学。我们还总结了FSC技术的发展,包括氮化硅薄膜芯片技术、快速扫描量热仪、商业化Flash DSC 1在不同高分子结晶熔融行为研究中的应用。然后介绍表征高分子等温结晶动力学的方法,其中包括样品制备、质量估算、消除热历史、临界扫描速率的确定等,并举例介绍FSC在高分子结晶动力学研究中的应用,涵盖高分子总结晶动力学、结晶成核动力学、高分子焓松弛对结晶成核的影响、FSC联用技术等方面。应用举例中对应形貌和结晶信息,分析了通过FSC测试得到的结晶成核动力学特点。另外通过比较不同结构特点的高分子,总结了我们对结晶动力学行为的基本理解。总之,FSC技术是一种能够提供相转变动力学和热力学信息的高效工具,特别是应用于分析只能在快速扫描中得到的样品结构变化信息。同时我们希望本文能够帮助读者考虑超快扫描量热技术在其他材料研究上的应用,包括合金、药物、生物大分子等。     

胶体与界面化学的研究进展

胶体与界面化学是研究胶体分散体系和界面现象的一门科学,在能源、材料、生物、化学制造和环境科学等领域具有广泛的应用。近年来,由于先进功能材料、仿生学和生物医药等学科的迅速发展,在纳米尺寸(胶体)的范围内进行分子组装和材料的制备已经引起了人们的高度关注。过去两年里,中国胶体与界面化学领域的科学家的创新性研究工作层出不穷,国际影响力日益提升,所获得的研究成果越来越受到国际同行的关注。这些成果可概括为:(1)系列新型有序分子组合体的构建及其在生物医药领域的应用,尤其是超分子组装、表面图案化有序组装材料的设计和应用;(2)胶体与界面化学方法在微纳米功能材料合成中的应用,包括形貌可控的无机材料、有机-无机复合功能材料、贵金属纳米材料以及小分子凝胶的合成及其应用;(3)胶体与界面化学在生物传感领域的新应用;(4)胶体与界面化学研究新方法。作为一门与实际应用密切结合的学科,现代经济社会为胶体与界面化学的发展提供了广阔的空间。可以预期,未来胶体与界面化学将更注重其基本的物理化学问题,如:新颖有序分子组合体的构建和理论认识;功能性微纳米材料界面结构与性能调控的理论指导。此外,新的手段和方法在胶体与界面体系的不断渗透,将不断产生新的学科交叉点,从而有力地促进胶体与界面化学的学科发展。共引用参考文献96篇。     

Lipids ofGossypium mexicanum

The surface lipids of the coat and the lipids of the kernel of the seeds of a wild form of the medium-fibered cotton plantGossypium mexicanum var.nervosum have been studied in comparison with cultured species. Using the methods of CC, TLC, and GLC, and UV and mass spectrometry, in the cuticular lipids ofG. mexicanum three classes of neutral lipids have been detected, and in the kernel lipids 10 classes of neutral lipids, 2 classes of glycolipids, and 7 classes of phospholipids. The structures of the epoxyacyl-, hydroxyacyl-, and diacylglycerols of the kernel have been established. The greatest differences between the seeds of the wild form of the cotton plant and the cultured species are the greater weight of the seed coat, the presence in it of a considerable amount of the 18:1 and of medium-molecular-weight fatty acids, and a higher level in the kernel of gossypol pigments, polar lipids, and acylglycerols containing the 18:2 acid.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 57–62, January–February, 1987.     

用ICP研究鹿科动物骨质疏松症的微量元素特征

鹿科动物的骨质疏松症是近几年出现的一种疾病，它影响鹿的生长发育和繁殖，病重者死亡。我们采集梅花鹿和白唇鹿的毛，血样，用低温灰化方法和温法消解处理样品，用ＩＣＰ分析了毛，血清中微量元素的含量。病梅花鹿毛样中Ｍｇ，Ａｌ，Ｃａ，Ｔｉ，Ｆｅ，Ｃｕ，Ｚｎ的含量比正常组高，Ｔｉ，Ｃｕ，Ｚｎ的偏差率大于１５％，而Ｓｉ，Ｍｎ，Ｐ，Ｐ，Ａｇ，Ｂａ，Ｌａ，Ｃｅ，Ｐｂ比正常组低，Ｖ，Ａｇ，Ｂａ，Ｌａ，Ｃｅ，Ｐｂ存在...     

生物热化学和热动力学研究进展

生命相关过程伴随着极其复杂的化学和物理过程,包含着物质变化和能量转换,其中部分能量不可避免地会以热的形式表现出来。用微量热技术和热动力学方法,研究复杂生命体系和相关反应的热动力学过程,可宏观地、本质地反映生命相关过程的内在规律。本文综述了生物量热学方法和技术在生命科学中的应用,介绍了生物量热技术在生态系统、生物组织和器官、细胞水平、亚细胞水平和分子层面等不同生物层次和结构水平上的研究现状和进展。     

几种不同进口“铅矿”的表征及属性分析研究

通过5种申报为“铅矿”的进口含铅物料的分析,发现铅矿伪报的现象时有发生,这些物料从外观上、铅含量上很难确认其真实属性,实验通过分析样品的理化特征,比对研究和文献查找的方法,分析进口含铅物料来源,进而获得属性判定的方法。其方法主要包括以下5个步骤:(1 )观察样品的外观性状,包括形状、粒度、颜色、手感、气味、磁性等特征;(2)测试样品的理化性质,包括元素组成、物相组成、微观形貌以及酸碱性等其他可能必要的信息;(3)对比研究所属申报品名的样品特征,即对铅矿样品进行比对研究；(4) 比对查证文献资料等,根据获得的样品的相关检测数据和铅矿信息,查阅相关的文献资料,对样品可能产生的来源进行查证分析; (5)确立样品的来源,从而确认样品的属性。     

高密度互连印制电路板孔金属化研究和进展

孔金属化互连是印制电路板（PCB）高密度集成的核心制程之一,化学镀铜和电子电镀铜是实现孔金属化的关键技术。本文介绍HDI-PCB的概念和制作流程;综述化学镀铜和电子电镀铜孔金属化互连的研究和进展,包括溶液组成和操作条件的影响,添加剂及其相互作用机理,以及盲孔填充和通孔孔壁加厚机制;展望高密度互连印制电路板电子电镀基础研究及新技术发展方向。     

微波消解-GFAAS测定浅水湖泊底泥中重金属元素

探讨了采用微波消解作为底泥样品的前处理方法,运用石墨炉原子吸收法测定浅水湖泊底泥中Cu,Pb,Zn,Cd,Cr含量的实验条件.方法的RSD为2.0％～4.1％,平均回收率为97.4％～101.5％,Cu,Pb,Zn,Cd,Cr的检出限分别为0.4,5,2.8,0.25,2.5ng.该法适合于浅水湖泊底泥中重金属含量的测定.     

Quantum-chemical calculations of the electronic structures of polymethylidyne dyes

The energies of the transitions of unsubstituted and substituted thia-, thiazolo-, and thienothiazolocarbocyanines, as well as quinocyanines and carbocyanines with a condensed thiophene, furan, selenophene, or pyridine ring, to the excited singlet states and their electronic structures were calculated by the MO LCAO method within the Pariser—Parr—Pople approximation. The nature of the long-wave and short-wave absorption bands in the spectra of these dyes and the peculiarities of the color of thieno-, furo-, and selenophenothiazolo- and -pyridocyanines, as well as the effect of substituents on their electronic characteristics as a function of the position in the heteroresidues and the nature of the latter, are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 626–633, May, 1978.     

用ETV-ICP-MS研究Cr、Ni、Zr、Nb、Yb在石墨炉中的蒸发/原子化机理

本文以电热蒸发电感耦合等离子体质谱（ETV-ICP-MS）为手段,探讨了Cr、Ni、Zr、Nb和Yb在石墨炉中的蒸发/原子化机理;比较了不同化学改进剂存在条件下,Cr、Ni、Zr、Nb和Yb的蒸发行为和在石墨炉原子吸收（GFAAS）中的原子化行为;考察了石墨炉温度和ICP功率等实验参数对上述元素发射强度及轮廓的影响.结果表明,Pd和Mg化合物的存在对Cr、Ni、Zr、Nb和Yb的蒸发/原子化行为没有明显的化学改进作用;然而,以聚四氟乙烯（PTFE）为化学改进剂时,可显著改善Cr、Ni、Zr、Nb和Yb的蒸发行为,避免难熔碳化物的形成,降低待测物的蒸发温度;对Cr和Ni的GFAAS信号强度略有增强;但是,由于Yb、Nb和Zr氟化物的离解键能很高,难以离解/原子化,PTFE的存在反而降低了Yb、Nb和Zr在GFAAS中的信号强度.     

初中生化学方程式前概念及其影响因素探查研究*

根据自编的“初中生化学方程式前概念及其影响因素”探查问卷,了解初中生可能在化学方程式的概念内涵(概念、意义、“+”和“=”的含义等)和外延(化学符号的重要性、化学方程式的唯一性、化学方程式与数学方程式的关系)方面存在的前概念认识,探查学生背景信息以及学习环境、学习方式、已有化学知识水平等外在因素的影响。对石家庄市某中学即将学习化学方程式的学生的176份有效问卷和8位学生的访谈分析结果表明,初中生化学方程式的前概念虽然在班级类型、数学成绩、课外书阅读类型、已有化学知识水平方面存在差异,很多已有认识与科学概念一致,但学生的认识并不全面,甚至有部分偏差认识。分析初中生化学方程式的前概念内容,建议化学方程式的教学重点是帮助学生从宏观与微观、定性与定量相结合角度认识化学方程式,理解不同化学符号的功能和价值。     

二维半导体材料纳米电子器件和光电器件

近年来,随着各领域对微电子器件集成度及性能要求的不断提高,发展基于二维半导体材料的新型高性能功能性器件成为了突破当前技术瓶颈的重要环节和关键方向。目前,作为新型二维半导体材料的代表,二维过渡金属二硫化物、二维黑磷以及范德瓦尔斯异质结凭借其在电学、热学、机械、光学等方面的优异性能已经成为了发展高性能纳米电子器件和光电器件的最具潜力的材料之一。在本综述中,首先概述了几种用于纳米器件的常见二维材料,分析了材料的结构、性能及其在纳米器件中的应用,其次重点对基于过渡金属二硫化物、黑磷以及由其衍生的范德瓦尔斯异质结的纳米电子器件和光电器件的最新研究进展进行讨论,最后对目前二维半导体纳米器件所面临的挑战以及未来的发展方向进行总结及分析,从而为未来发展高性能功能性纳米器件提供支持。