尼龙1010扩链反应的动力学模型和分析

双唑啉类化合物通过唑啉环与尼龙端羧基的开环加成反应使尼龙 10 10的分子量大幅提高 .以线性扩链反应的理想动力学模型为基础 ,通过对关键因素的修正使其更好地符合聚合物高粘度熔体扩链反应的实际过程 .通过数值积分方法 ,可以方便地模拟关键因素对扩链反应的影响 .理想线性模型与熔融扩链反应的前期规律相符合 ,但是其未考虑后期扩链产物的降解对偶联效果造成的影响 .通过基于降解的修正 ,该模型更好地符合了实际情况 .在扩链过程中 ,反应速率k和唑啉环与端羧基的比r是控制偶联效果的关键因素 ,温度和扩链剂加入量可以通过改变k和r进行方便的分析 .由于PA熔体反应体系的高粘性 ,2 ,2′ 双 (2 唑啉 ) (BOZ)和 1,4 双 (2 唑啉基 )苯 (PBO)的扩链效果的差别得以解释     

聚乳酸扩链改性研究进展

扩链反应是聚酯类材料生产和回收利用的一种有效手段。聚乳酸是一种新型的可生物降解类聚酯,但脆性大、耐热性差等缺点限制了其应用。扩链反应不仅能够提高聚乳酸的分子量,而且还能通过化学反应引入其它官能团来改善其韧性或赋予其某种功能,对拓展聚乳酸的应用范围具有重要意义。此外,对回收聚乳酸进行扩链增粘来实现材料重复利用也显示出了良好的发展前景。本文主要从扩链剂的种类及其反应机理、扩链改性的应用等方面综述了近年来国内外聚乳酸扩链改性的研究进展,并对其今后的发展方向进行了展望。     

MDI与TDI封端聚酯预聚物和扩链剂间反应速率的研究

用ＦＴＩＲ法系统地研究了不同硬段结构对聚酯型聚氨酯扩链反应动力学的影响，结果显示：不同类二异氰酸酯ＭＤＩ和ＴＤＩ形成的ＮＣＯ封端的聚酯预聚体与二元胺（ＭＯＣＡ）和三元醇（ＴＭＰ）的扩链反应均为二级反应，由ＭＤＩ形成ＮＣＯ封端的聚酯预聚体与胺或醇的扩链反应速度比ＴＤＩ类的要快，ＭＯＣＡ扩链比ＴＭＰ扩链反应活化能低，从基团反应活性不同体系扩链反速度的差别进行了讨论。     

镨气相扩渗PbTiO3陶瓷的制备及其电性能

采用气相化学热扩渗方法制备了Pr改性的PbTiO3陶瓷,并对扩渗后PbTiO3陶瓷的组成、结构及电性能的变化进行了研究。通过XRD,SEM及Pr元素的面扫描分析证实Pr元素已经渗入到PbTiO3陶瓷体相,且分布均匀,并生成了Pr2Ti2O7等新的化合物,由此导致了PbTiO3陶瓷导电性的显著增强。在Pr扩渗PbTiO3陶瓷的实验中,通过正交试验法确定了扩渗的最佳工艺条件,即Pr元素的扩渗质量分数为0.015,扩渗时间为3 h,扩渗温度为860℃,此时PbTiO3陶瓷的导电性最好,其室温电阻率从2.0×1010下降为9.487Ω·m。对改性的PbTiO3陶瓷进行了交流复阻抗分析,随着温度的升高,扩渗后的PbTiO3陶瓷的导电性更强,其晶粒电阻和晶界电阻均随温度升高而呈逐渐下降的趋势,已不存在PTC效应,有向导电体过渡趋势。     

双噁唑啉扩链尼龙1010

对尼龙 10 10的加成型化学扩链做了系统的研究 ,并对 2 ,2′ 双 (2 唑啉 ) (BOZ)和 1,4 双 (2 唑啉基 )苯 (PBO)的偶联效果和扩链产物的性能做了详细的探讨 ,前者的扩链效果较好 .研究结果表明 ,尼龙10 10熔体的转矩随着反应时间的延长显著增加 .但转矩达到极大值后开始缓慢下降 ,表明扩链产物在高温条件下发生热降解 .扩链剂的用量存在最佳值 ,用量不足时偶联反应不充分 ,用量过量时封端反应加剧 .扩链以后尼龙 10 10的端羧基含量大大降低 ,反应温度对反应速率的影响符合阿累尼乌斯关系式 .扩链产物极限粘度大大高于尼龙原料 ,表明分子量显著提高     

聚对苯二甲酸乙醇酯和聚对苯二甲酸丁二醇酯化学扩链反应

综述了用于聚对苯二甲酸乙二醇酯和聚对苯二甲酸丁二醇酯聚对苯二甲酸丁二醇酯化学扩链反应的羧基加成型和羟基加成型扩链剂，以及缩合型扩链反应，羧基加成型扩链反应和羟基加成型扩链反应、羟羟基同时加成型扩链反应。     

扩链法合成聚乳酸类生物降解材料

详细地综述了聚乳酸类生物降解材料的扩链法合成，特别是使用二异氰酸酯类、二恶唑淋类扩链剂的合成进展。参考文献37篇。     

Pt/HZSM-5催化剂上甲基环戊烷的临氢转化 Ⅰ.反应条件对扩环反应的影响

在连续流固定床反应装置上,考察了反应温度、压力及氢烃摩尔比等条件对甲基环戊烷(MCP)临氢转化反应活性及扩环反应选择性的影响;结合反应评价结果和热力学分析,探讨了Pt/HZSM-5催化作用下MCP的扩环反应规律.MCP临氢转化发生三类反应:扩环(RE)、开环(RO)和裂解(CR),其中扩环反应生成环己烷(CH)和苯(Bz).结果表明,随温度的升高或氢烃比的降低,MCP的转化率增大,而提高反应压力不利于MCP的转化.扩环反应选择性呈现复杂的变化规律,随温度的升高,扩环反应选择性先增加而后逐渐降低,即存在极大值.氢烃比的影响与温度密切相关,在低温区时扩环反应的选择性随氢烃比的降低而降低,而在高温区时的影响很小.提高反应压力,对扩环反应不利.扩环产物Bz和CH的分布为MCP扩环反应的反应历程提供了信息,临氢反应的Bz/CH实验值大于理论平衡值的结果表明,与CH相同,Bz也是MCP临氢转化的一次产物.在此基础上提出了修正的MCP扩环反应历程,MCP在双功能催化剂作用下形成的中间体吸附物种,通过两条平行反应路径分别生成CH和Bz,即异构化反应和异构脱氢反应是平行反应.同时,在本催化反应体系下,Bz还可以由CH脱氢而来.     

扩环氮杂环卡宾前体鎓盐的合成进展

氮杂环卡宾(N-heterocyclic carbenes,NHCs)作为一种新兴配体,在现代有机化学中有非常重要的应用.有关NHCs的初期研究较多集中在易于合成、性质稳定的咪唑衍生五元-NHCs及其金属化合物,近年研究发现的六元、七元等扩环-NHCs,由于其独特的立体和化学特性而成为现代有机化学的又一研究热点.氮杂环鎓盐去质子化是获得NHCs的常用方法,因而扩环-NHCs前体鎓盐的合成是影响扩环-NHCs研究进展的一个重要因素,就近年来扩环-NHCs前体鎓盐的合成进展作一综述.     

含柔性间隔基的扩链脲增韧环氧树脂性能研究——环氧树脂／扩链脲／双氰双胺体系性能研究

合成了含不同分子量柔性间隔基的扩链脲（Ｕｉ），并对其与双氰双胺共同固化环氧树脂体系的反应活性、抗冲击性能、动态力学性能、形态结构及贮存性能进行了考察。结果表明：含分子量为４００的聚乙二醇柔性链的扩链脲／双氰双胺／环氧树脂固化体系的抗冲击强度较单纯双氰双胺／环氧树脂固化体系提高了７倍左右，其冲击试样断面电镜照片呈韧性断裂的特征。扩链脲的反应活性基本不受分子中聚乙二醇链段分子量的影响。环氧树脂／扩链脲／双氰双胺体系在５０℃下贮存期可达１～２天。     

Evaluation of the aerobic composting process of winery and distillery residues by thermal methods

The possibility of using thermal analysis for a quick characterization of chemical changes was tested in the organic matter from composting materials. Differential thermal analysis (DTA), thermogravimetry (TG) and the first derivative of the TG (DTG) were calculated in oxidizing conditions on compost samples obtained from three composting piles. The composting piles were made by mixing winery and distillery residues with sewage sludge (pile 1), with cow manure (pile 2) and hen droppings (pile 3). The temperature values in the pile 1 showed a different evolution during the thermophilic stage of the composting process in relation to the piles 2 and 3. The thermophilic stage for pile 1 was 17 days, meanwhile for the piles 2 and 3 were around 80 and 110 days, respectively, and probably pile 1 was not well composted. The curves of ion current of CO₂ have been recorded in order to shed light on changes occurring in organic matter during composting. Particularly DTG curves allowed us to distinguish between well (piles 2 and 3) and poor (pile 1) stabilized organic matter. The energy released was calculated for each sample by integrating the DTA curves and these results are agreed with the previous hypothesis. Information deriving from weight losses, registered by the TG and DTG curves, enables to follow the evolution state of the organic matter and therefore changes in its stability. These data could determine the final point of the composting process of winery and distillery residues and then reduce the time for compost harvest.     

Behaviour of Extractives in Norway Spruce (Picea abies) Bark during Pile Storage

The current practices regarding the procurement chain of forest industry sidestreams, such as conifer bark, do not always lead to optimal conditions for preserving individual chemical compounds. This study investigates the standard way of storing bark in large piles in an open area. We mainly focus on the degradation of the most essential hydrophilic and hydrophobic extractives and carbohydrates. First, two large 450 m³ piles of bark from Norway spruce (Picea abies) were formed, one of which was covered with snow. The degradation of the bark extractives was monitored for 24 weeks. Samples were taken from the middle, side and top of the pile. Each sample was extracted at 120 °C with both n-hexane and water, and the extracts produced were then analysed chromatographically using gas chromatography with flame ionisation or mass selective detection and high-performance liquid chromatography. The carbohydrates were next analysed using acidic hydrolysis and acidic methanolysis, followed by chromatographic separation of the monosaccharides formed and their derivatives. The results showed that the most intensive degradation occurred during the first 4 weeks of storage. The levels of hydrophilic extractives were also found to decrease drastically (69% in normal pile and 73% in snow-covered pile) during storage, whereas the decrease in hydrophobic extractives was relatively stable (15% in normal pile and 8% in snow-covered pile). The top of the piles exhibited the most significant decrease in the total level of extractives (73% in normal and snow-covered pile), whereas the bark in the middle of the pile retained the highest amount of extractives (decreased by 51% in normal pile and 47% in snow-covered pile) after 24-week storage.     

Assessment of radioecological situation of a site contaminated by technologically enhanced natural radioactivity in Croatia

The paper deals with radioactivity contamination originating from the coal fired power plant and its waste dumps located in a bay of the Adriatic which is due to geographical characteristics sensitive to any kind of pollution including radioactivity. Investigations of coal used in regular plant operation and of solid incombustible ash and slag showed increased concentrations of natural radioactivity which may cause general environmental contamination of the bay as well as contamination of the marine environment of this part of Croatian Adriatic. There are two coal slag and ash piles, one of them was closed and covered by soil and the other is a still operating pile. The location of both piles presents a considerable environmental problem: situated close to the seaside, slag and ash are accumulating in the littoral zone and, in the case of operating pile, are being filled-up directly into the sea. The aim of this study was to determine the radioactivity level at the ash and slag deposits and to assess the risk of increased radioactivity for the inhabitants of the nearby urban area, for the plant workers and general environment of the bay including the marine environment of this part of the Croatian Adriatic.     

A comparative analysis of self-assembly in poly(methacrylates) with bulky side substituents of different molecular masses in the solid state and in solutions

A comparative investigation of self-assembly in poly(methacrylates) with bulky substituents based on gallic acid both in the condensed state and in hexane solutions has been performed by using the methods of SAXS and DSC. The size and shape of the formed supramolecular aggregates have been analyzed for the polymers of two different degrees of polymerization (150 and 21). In fresh solutions of a low-molecular-mass polymer, extended piles composed of several molecules are formed. Each molecule from a disk with a diameter of ～4.4 nm, which is similar to the diameter of columnar phase cylinders in the solid state. In solutions of a highmolecular-mass polymer, several molecules form a wormlike particle. The observed supramolecular aggregates are unstable: within several months, their order breaks down and particles are dissolved.     

煤中15种微量元素在燃烧产物中的分配

建立了燃煤中１５种向量元素在悄灰和底灰中含量分布的经验公式，该公式可以估算煤中微量元素在燃烧产物中的分配及传输通量。煤中非挥发性元素大部分存在于底灰和飞灰中，挥发性元素进入大气的量较高。     

Partitioning of natural radionuclides in sediments around a former uranium mine and mill

Partitioning of natural radionuclides in sediments from streams affected by the waste piles of the former uranium mine and mill located at ?irovski vrh, Slovenia, was performed by applying a sequential extraction procedure. The sediments were collected at three sites located upstream and three sites located downstream of the waste piles. Then the four-step Community Bureau of Reference (BCR) sequential extraction protocol was applied to the samples and the natural radionuclides ²³⁸U, ²³⁰Th, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po were analysed in each extraction fraction. It was expected that the fractionation of natural radionuclides originating from the waste piles would differ from that upstream of the influence of waste piles because their chemical environment had been altered during the processes of uranium extraction. This difference could allow tracing of the radionuclides coming from the waste piles downstream of the affected watercourses. The results definitely showed that the total activity concentrations at sites downstream of the influence of the waste piles were higher than at sites upstream of the piles. However, this difference was geographically very limited and could no longer be detected already at a distance of about 5 km downstream. Unexpectedly, the fractionation of radionuclides upstream and downstream of the area of influence of the waste piles did not appear to be significantly altered. The sole differences found were for ²³⁸U and ²²⁶Ra in the second fraction (the “Fe/Mn oxides” fraction) and for ²¹⁰Po in the fourth fraction (the “residue” fraction) of the BCR sequential extraction protocol.     

Proteins in Countryclub-Like Jails:Encapsulation of Enzymes in Nanoporous Materials

A popular method for enzyme immobilization is formation of covalent bonds between enzymes and a solid support, which often alters the enzymatic activities. Recently, various enzymes have been entrapped in inorganic oxides such as silica for biocatalysis and biosensor applications through conventional sol-gel process. However, because of the microporous nature (i.e. pore diameter of 1.5-2 nm or less) of conventional sol-gels, the activities of enzymes are hindered by low diffusion rates of substrate molecules and poor accessibility of enzymes inside the materials.     

Synthesis of Discrete Alkyl‐Silica Hybrid Nanowires and Their Assembly into Nanostructured Superhydrophobic Membranes

We report the synthesis of highly flexible and mechanically robust hybrid silica nanowires (NWs) which can be used as novel building blocks to construct superhydrophobic functional materials with three‐dimensional macroporous networks. The hybrid silica NWs, with an average diameter of 80 nm and tunable length of up to 12 μm, are prepared by anisotropic deposition of the hydrolyzed tetraethylorthosilicate in water/n‐pentanol emulsions. A mechanistic investigation reveals that the trimethoxy(octadecyl)silane introduced to the water‐oil interface in the synthesis plays key roles in stabilizing the water droplets to sub‐100 nm and also growing a layer of octadecyl groups on the NW surface. This work opens a solution‐based route for the one‐pot preparation of monodisperse, hydrophobic silica NWs and represents an important step toward the bottom‐up construction of 3D superhydrophobic materials and macroporous membranes.     

On-chip extrusion of lipid vesicles and tubes through microsized apertures

In this work we present the formation of micrometre-sized lipid vesicles and tubes with perfectly homogeneous diameter and extraordinary length. The method is a novel approach for unconventional fabrication of soft-matter microstructured devices based on the combination of top-down and bottom-up fabrication processes. Photolithography techniques are applied to fabricate microsized apertures that provide the requirements to form lipid structures with predictable size and to align and guide the vesicles and tubes in microstructured channels. The formation is facilitated by self-assembly of polar lipids to a lipid membrane that is afterwards forced to undergo a shape transformation by extrusion through a microsized aperture. Both the geometrical restriction by the small aperture and the pressure difference between the top and bottom sides of the aperture determine the form and length of the vesicles and tubes. A strong pressure difference favors the formation of lipid tubes, while a low pressure difference results in the formation of vesicle bunches with spherical and cylindrical shapes. Potential applications for the formed lipid structures could be as microreactors and transport channels as well as in the construction of flexible microfluidic networks.     

Secondary ion mass spectrometry depth profiling of ultrathick films using an argon gas cluster source: Crater shape implications on the analysis area as a function of depth

Argon cluster ions have enabled molecular depth profiling to unprecedented depths, with minimal loss of chemical information or changes in sputter rate. However, depth profiling of ultrathick films (>100 μm) using a commercial ion source oriented at 45° to the surface causes the crater bottom to shrink in size because of a combination of the crater wall angle, sputter rate differences along the trailing-edge crater wall, and undercutting on the leading-edge. The shrinking of the crater bottom has 2 immediate effects on dual-beam depth profiling: first is that the centering of the analysis beam inside the sputter crater will no longer ensure the best quality depth profile because the location of the flat crater bottom progressively shifts toward the leading-edge and second, the shifting of the crater bottom enforces a maximum thickness of the film that could be depth profiled. Experiments demonstrate that a time-of-flight secondary ion mass spectrometry instrument equipped with a 20 keV argon cluster source is limited to depth profiling a 180 μm-thick film when a 500 μm sputter raster is used and a 100 μm square crater bottom is to be left for analysis. In addition, depth profiling of a multilayer film revealed that the depth resolution degrades on trailing-edge side of the crater bottom presumably because of the redeposition of the sputtered flux from the crater wall onto the crater bottom.