共查询到20条相似文献,搜索用时 78 毫秒
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N-杂环卡宾配体的优异催化性能引起了人们的广泛关注, 已成功应用于多种烯烃聚合反应。本文结合N-杂环卡宾的相关研究报道,首先简要介绍N-杂环卡宾,随后重点介绍N-杂环卡宾在开环易位聚合、烯烃配位聚合和原子转移自由基聚合等聚合反应的应用。在此基础上,指出了今后N-杂环卡宾配体在聚合反应研究的发展方向。 相似文献
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新型螺环单体的合成和自由基聚合反应的研究王宏鲁剑涛冯品珍(中国科学技术大学研究生院化学部北京100039)关键词自由基聚合,新单体合成,螺环单体,自由基共聚虽然离子型开环聚合早已为人熟知,但是自由基开环聚合反应的研究和应用开发还刚刚起步.... 相似文献
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平均聚合度和聚合度分布是决定聚合物产品质量的一个重要指标。平均聚合度直接表征聚合产品的分子量的大小,它的大小又决定高分子材料的性能,因此,研究平均聚合度具有重要的理论意义和实际意义。聚合反应按机理分类,可分为链型聚合和逐步聚合,链型聚合又分为自由基聚合、离子聚合、配位聚合,逐步聚合又分为缩聚和加聚反应。本文以自由基聚合、离子聚合、配位聚合以及缩聚的聚合机理为主线,对不同聚合机理对应的平均聚合度的公式进行推导和讨论,并加深理解,掌握其内涵。旨在提高学生对平均聚合度的认识和把握。 相似文献
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活性 (或称可控 )自由基聚合研究是目前高分子科学的研究热点之一[1~ 8] .活性自由基聚合制备的聚合物具有分子量随转化率提高而线性增加、分子量分布窄和聚合反应为一级反应动力学等特点 .自由基开环聚合所得产物体积收缩小 ,某些含有不饱和双键的螺环单体发生双开环聚合时甚至发生体积膨胀 ;开环聚合还可在聚合物主链上引入各种官能团 ,如酯基、碳酸酯基、酮基等 [9~ 12 ] .因此 ,用活性聚合的方法对自由基开环聚合的分子量和分子量分布进行控制 ,可以制备出具有各种不同结构和性能的新聚合物 . Wei等 [13] 报道了利用稳定自由基法实现… 相似文献
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利用当前通用的多媒体技术、以多媒体制作工具Authorware为主,高级语言VB及其它一些主流的媒体创作工具为辅,设计了高分子化学多媒体教学系统。它由八个模块组成,即绪论、自由基聚合、自由基共聚合、离子聚合反应、配位聚合反应、连锁聚合实施方法、逐步聚合反应、聚合物的化学反应。每个模块又分为四部分,即具体章节、本章要求、知识拓展及课后作业。采用接口技术,实现了内容的录入、删除、修改、访查以及资料查阅等诸多功能。它不仅可以作为高分子化学课程课堂教学使用,又可作为本专业学生及相关专业学生有效地进行高分子化学课后复习、习题训练、自学并阅读课外参考资料。该教学系统使用方便、操作简单、针对性强,是一种较实用的计算机辅助教学工具。 相似文献
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本文较为全面地综述了Gaussian-1,Gaussian-2(简称G1,G2)理论以及简化的G2(MP2),G2(MP3)理论,将其主要结果进行了比较分析。关于G2理论的应用,除了较为详细地综述了几年来理论在重现实验数据、评价实验数据、预测实验数据及研究化学反应途径等方面的应用外,还结合我们近期研究结果的主要结论讨论了该理论在研究等电子-等自旋,价层等电-等旋,等旋及非等旋化学反应的能量计算中的应用情况,以及该理论在预测化合物的标准生成焓方面的应用情况。 相似文献
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Tadeusz Kosztoowicz 《Journal of membrane science》2008,320(1-2):492-499
We theoretically study subdiffusion in a system, in which homogeneous thick membrane separates two media; in each of them there are different subdiffusion parameters. Subdiffusion is described by the linear differential equations with fractional time derivative and the boundary conditions requiring that the ratio of substance concentrations on both sides of the membrane surface is constant in time. Starting with the Green’s functions derived for the considered system, we discuss the property of the concentrations found in the long time limit for the system where initially the membrane separates pure solvent from homogeneous solution. 相似文献
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本文较为全面地综述了Gaussian-1, Gaussian-2(简称G1,G2)理论以及简化的G2 CMP2 ) ,G2 (MP3)理论,将其主要结果进行了比较分析。关于G2理论的应用,除了较为详细地综述了几年来理论在重现实验数据、评价实验数据、预测实验数据及研究化学反应途径等方面的应用外,还结合我仁近期研究结果的主要结论讨论了该理论在研究等电子一等自旋,价层等电一等旋,等旋及非等旋化学反应的能量计算中的应用情况,以及该理论在预测化合物的标准生成蛤方面的应用情况。 相似文献
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J. C. Giddings 《Journal of separation science》1987,10(5):319-323
Multidimensional separation methodology provides a mechanism for a very substantial increase in the resolving power of chromatographic and related systems. After defining the conditions required for multidimensional separation and reviewing the origin of its high resolving power, a comparison is drawn between the two principal kinds of multidimensional systems, represented by continuous two-dimensional operation and coupled column assemblies. It is shown that their roles are complementary. The two-dimensional system gives a broad powerful overview of a sample while the coupled column system can be used flexibly to magnify and resolve selected regions of the sample space. 相似文献
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Dr. Qin Yang Prof. Julien Bloino Hana Šestáková Dr. Jaroslav Šebestík Dr. Jiří Kessler Dr. Jana Hudecová Dr. Josef Kapitán Prof. Petr Bouř 《Angewandte Chemie (International ed. in English)》2023,62(45):e202312521
Resonance Raman optical activity (RROA) spectra with high sensitivity reveal details on molecular structure, chirality, and excited electronic properties. Despite the difficulty of the measurements, the recorded data for the Co(III) complex with S,S-N,N-ethylenediaminedisuccinic acid are of exceptional quality and, coupled with the theory, spectacularly document the molecular behavior in resonance. This includes a huge enhancement of the chiral scattering, contribution of the antisymmetric polarizabilities to the signal, and the Herzberg-Teller effect significantly shaping the spectra. The chiral component is by about one order of magnitude bigger than for an analogous aluminum complex. The band assignment and intensity profile were confirmed by simulations based on density functional and vibronic theories. The resonance was attributed to the S0→S3 transition, with the strongest signal enhancement of Raman and ROA spectral bands below about 800 cm−1. For higher wavenumbers, other excited electronic states contribute to the scattering in a less resonant way. RROA spectroscopy thus appears as a unique tool to study the structure and electronic states of absorbing molecules in analytical chemistry, biology, and material science. 相似文献
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Raghubir Singh Varinder Kaur Chahal Raj Pal Sharma Paloth Venugopalan 《Journal of organometallic chemistry》2010,695(2):183-1348
A novel silatrane containing Si ← N bond (2.160 Å), has been synthesized by the reaction of 3-aminopropylsilatrane (1), dicyclohexylcarbodiimide (2) and CS2. The structure was established by elemental analysis, spectroscopic methods (IR, 1H NMR, 13C NMR and Mass spectroscopy) and X-ray crystallography. It was correlated with theoretical studies such as semiempirical (AM1, PM3, PM3MM and MNDO), Density Functional Theory (B3LYP) and Hartree-Fock at 3-21+G∗ and 6-31G∗(d) levels. The reactivity of compound 3 was studied with some Lewis acids and bases that showed the formation of corresponding adducts (4-7), which were characterized by elemental analysis, IR and NMR (1H, 13C) spectroscopy. 相似文献
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We study the interaction between two like charged surfaces embedded in a solution of oppositely charged multivalent rod-like counterions.The counterions consist of two rigidly bonded point charges,each of valency Z.The strength of the electrostatic coupling increases with increasing surface charge density or valency of the charges.The system is analyzed by employing a self-consistent field theory,which treats the short and long range interactions of the counterions within different approximations.We find that in the weak coupling limit,the interactions are only repulsive.In the intermediate coupling regime,the multivalent rod-like counterions can mediate attractive interactions between the surfaces. For sufficiently long rods,bridging contributes to the attractive interaction.In the strong coupling limit,the charge correlations can contribute to the attractive interactions at short separations between the charged surfaces.Two minima can then appear in the force curve between surfaces. 相似文献
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Kinetic measurements for the forward reaction Fe(CN)54-AmPy3? + Co(edta)? ? Fe(CN)5s4-AmPy2? + Co(edta)2? have been carried out; the rate constant is 2.72 ± 0.07 M?1s?1, at pH = 8, μ = 0.10 M LiClO4, and T = 25°C. The activation parameters of the reaction were also studied with and . The mechanism of the reaction is discussed in the context of the Marcus cross relation for an outer-sphere process. 相似文献
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Systems of differential rate equations characteristic for several basic types of plasma chemical reactions have been obtained. Every system permits one to reproduce a full kinetic picture of the reaction (kinetic curves of the starting, intermediate, and final compounds) and identify its mechanism by comparing this picture with the experimental kinetic pattern. The four important cases of a gas-phase plasma polymerization were considered in detail: radical propagating chain and stepwise recombination–activation, each having two different mechanisms of the death of plasma radicals. A comparison between the theoretical and experimental (mass spectrometry) kinetic patterns of six starting monomers and their low-molecular-weight products has established the chain mechanism predominating in all cases at the initial stages of the synthesis. 相似文献