共查询到18条相似文献,搜索用时 171 毫秒
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利用SSA和13 C-NMR技术研究了Donor-C和Donor-N复配的外给电子体(C/N型复合外给电子体)对聚丙烯的热性能及分子链中的等规序列长度的影响。研究发现,在丙烯聚合中加入C/N型复合外给电子体不仅可以提高催化剂的催化性能,而且可以对制备的聚丙烯链的微观结构产生重要的影响。随着Donor-C在C/N型复合外给电子体中含量的升高,SSA结果表明,聚丙烯的结晶能力逐渐增强,分子链中的各等规序列长度逐渐变长;13 C-NMR结果表明,分子链的平均序列长度也随着Donor-C在C/N型复合外给电子体中含量逐渐升高而增加。 相似文献
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综述了丙烯聚合用Ziegler—Natta催化剂内、外给电子体的最新进展:内给电子体主要包括1,3-二醚、二醇酯、琥珀酸酯和1-醚-3-酮化合物.外给电子体主要包括复合外给电子体以及含氮硅烷化合物。消费者对聚丙烯材料的清洁性要求越来越高,因此聚丙烯催化剂内、外给电子供体的发展不仅要求能够制备出更高性能的聚丙烯,同时还要... 相似文献
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分子量分布是聚丙烯产品的一个重要参数,直接影响材料的使用和应用,关于聚丙烯分子量和分子量分布的控制和影响因素的研究对于工业界和学术研究都有十分重要的意义。本文主要从催化剂组成、聚合条件等方面对Ziegler-Natta催化体系中影响聚丙烯分子量分布的因素进行了详细的综述。在催化剂组成方面,主要讨论了内给电子体、外给电子体及给电子体复合技术对聚丙烯分子量分布的影响;在聚合条件方面,主要讨论了聚合时间、聚合温度、助催化剂、聚合工艺对聚丙烯分子量分布的影响。 相似文献
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合成了2种新型硅烷化合物双环己基二甲氧基硅烷(Donor-H)、双哌啶二甲氧基硅烷(Donor-Py),将其与工业化的环己基甲基二甲氧基硅烷(Donor-C)分别作为外给电子体,用于MgCl2负载的Ziegler-Natta催化剂催化丙烯聚合,通过DSC、GPC、SSA和13C-NMR等分析手段研究了3种外给电子体取代基的变化对催化剂的催化活性、氢调敏感性、聚丙烯的等规度、分子量分布、结晶能力、等规序列分布的影响.结果表明,随着外给电子体取代基体积的增大,外给电子体的给电子能力逐渐增强.与Donor-C相比,随着外给电子体取代基体积的增大,合成的具有较大取代基的Donor-H和Donor-Py用于丙烯聚合时都表现优异的催化性能,特别是新型含有N杂原子的氨基硅烷类Donor-Py为外给电子体的催化剂的催化活性和制备的聚丙烯的等规度最高,聚丙烯的熔融指数可调范围最宽,结晶能力更强.氨基硅烷类Donor-Py制备的聚丙烯SSA热分级后的高等规组分含量最多,可高达64.5%,聚丙烯等规序列长度最长,聚丙烯的等规序列分布最窄,而且13C-NMR结果也表明聚丙烯等规序列长度MSL最长,聚丙烯的分子链最规整. 相似文献
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新型非对称二醚给电子体丙烯聚合催化剂研究 总被引:15,自引:0,他引:15
1,3-丙二醚类化合物为给电子体合成的新一类复相Ziegler-Natta催化剂(Z-N催化剂),其用于丙烯聚合时,在无需外加给电子体的情况下,可得到高活性的催化剂和高等规度的聚丙烯,催化剂的活性是以邻苯二甲酸二丁酯为内给电子体合成的Z-N催化剂的2~3倍,且得到聚丙烯的等规度大于95%[1-4].由于1,3-丙二醚类化合物与载体的配位作用较强,不易与AlR3反应,因此在丙烯聚合时无需外给电子体,并能降低反应体系的复杂性,有利于研究活性中心结构和聚合机理[5-7].以往研究均采用对称结构的 1,3-丙二醚类化合物作内给电子体[2-7],其结构如 Scheme 1 所示.本文采用一种新的 相似文献
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用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展 总被引:10,自引:0,他引:10
综述了用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展,包括内给电子体的发展及其作用研究,催化剂活性中心的模型,用MgCl2负载的Z-N催化剂制备抗冲聚丙烯合金. 相似文献
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为了得到具有高的临界转变温度的有机超导体,我们设计并合成了新的有机电子给体Twin—ET 和[2,2]-ET—Phane。并对 Twin-ET 的性质进行了研究。 相似文献
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通过[RuHCl(CO)(PPh3)2(B)] (B=PPh3, 吡啶 (py), 哌啶 (pip), 吗啉 (morph))与适当的席夫碱按1∶1的物质的量的比反应,合成了二齿和四齿席夫碱钌(Ⅱ)配合物。所用席夫碱配体通过S-苄基二硫代肼基甲酸酯与2,3-丁二酮(物质的量的比分别为1∶1和1∶2)的缩合反应制得。通过元素分析和多种物理化学方法对钌(Ⅱ)配合物和其席夫碱配体进行了表征。钌(Ⅱ)配合物为六配位的反磁性物质。用三种细菌对席夫碱配体及其钌(Ⅱ)配合物的抗微生物活性进行了筛选试验。 相似文献
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Lauren C. Irwin Meredith A. Allen Matthew R. Vriesen Prof. Michael A. Kerr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(1):171-175
Novel oxime-ether tethered cyclopropanes, when exposed to Yb(OTf)3 and heat, annulate to generate hydropyrrolo-oxazines products that can be taken to their respective pyrrolidines via hydrogenative N−O bond cleavage. The hydropyrrolo-oxazines are generated in a diastereoselective manner isolating the cis or trans product based on the temperature of the reaction. 20 examples of selective cis and trans hydropyrrolo-oxazines were generated in high yields by temperature control. 相似文献
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Dr. Shang-Fu Yuan Wen-Di Liu Dr. Chun-Yu Liu Dr. Zong-Jie Guan Prof. Dr. Quan-Ming Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(24):e202104445
Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have not been used in the protection for well-defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor-protected metal nanoclusters in terms of structural and functional modulation. 相似文献
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Charu Popli Youngwoo Jang Yuvraj Patil Prof. Dr. Rajneesh Misra Prof. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15109-15115
The significance of multiple number of donor–acceptor entities on a central electron donor in a star-shaped molecular system in improving light energy harvesting ability is reported. For this, donor–acceptor–donor type conjugates comprised up to three entities ferrocenyl (Fc)-diketopyrrolopyrrole (DPP) onto a central triphenylamine (TPA), ( 4 – 6 ) by the Pd-catalyzed Sonogashira cross-coupling reactions have been newly synthesized and characterized. Donor–acceptor conjugates possessing diketopyrrolopyrrole (1 to 3 entities) onto the central triphenylamine, ( 1 – 3 ) served as reference dyads while monomeric DPP and Fc-DPP served as control compounds. Both DPP and Fc-DPP carrying conjugates exhibited red-shifted absorption compared to their respective control compounds revealing existence of ground state interactions. Furthermore, DPP fluorescence in 4 – 6 was found to be quantitatively quenched while for 1 – 3 , this property varied between 73–65 % suggesting occurrence moderate amounts of excited state events. The electrochemical investigations exhibited an additional low potential oxidation in the case of Fc-DPP-TPA based derivatives ( 4 – 6 ) owing to the presence of ferrocene unit(s). This was in addition to DPP and TPA redox peaks. Using spectral, electrochemical and computational studies, Gibbs free-energy calculations were performed to visualize excited state charge separation (ΔGCS) in these donor–acceptor conjugates as a function of different number of Fc-DPP entities. Formation of Fc+-DPP.−-TPA charge separated states (CSS) in the case of 4 – 6 was evident. Using spectroelectrochemical studies, spectrum of CSS was deduced. Finally, femtosecond transient absorption spectral studies were performed to gather information on excited state charge separation. Increasing the number of Fc-DPP entities in 4 – 6 improved charge separation rates. Surprisingly, lifetime of the charge separated state, Fc+-DPP.−-TPA was found to persist longer with an increase in the number of Fc-DPP entities in 4 – 6 as compared to Fc-DPP-control and simple DPP derived donor–acceptor conjugates in literature. This unprecedented result has been attributed to subtle changes in ΔGCS and ΔGCR and the associated electron coupling between different entities. 相似文献
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Two novel copper(I) complexes with Cu‐O bonds, [Cu2L2(PPh3)2](BF4)2 ( 1 ) and [Cu(L)(dppeo)](BF4) ( 2 ) ( L = 6‐(4‐diethylmethylphosphonatephenyl)‐2,2′‐bipyridine, dppeo = bis(diphenylphosphino)ethane monoxide), have been prepared and their structures characterized. In the binuclear complex 1 , the ligand L serves as tridentate donor with the N, N′ and O as coordination atoms, and the two CuI atoms are bridged through both P = O donor atoms in different ligand L with a triphenylphosphine molecule as auxiliary ligand. While in mononuclear complex 2 , both ligands L and dppeo behave as bidentate with N∧N from L and P∧O from dppeo chelating to CuI atom. 相似文献
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Miranda M. Sroda Friedrich Stricker Julie A. Peterson Alexandria Bernal Prof. Javier Read de Alaniz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):4183-4190
The effects of solution-state dielectric and intermolecular interactions on the degree of charge separation provide a route to understanding the switching properties and concentration dependence of donor–acceptor Stenhouse adducts (DASAs). Through solvatochromic analysis of the open-form DASA in conjunction with X-ray diffraction and computational theory, we have analyzed the ionic character of a series of DASAs. First- and third-generation architectures lead to a higher zwitterionic resonance contribution of the open form and a zwitterionic closed form, whereas the second-generation architecture possesses a less charge-separated open form and neutral closed form. This can be correlated with equilibrium control and photoswitching solvent compatibility. As a result of the high contribution of the zwitterionic resonance forms of first- and third-generation DASAs, we were able to control their switching kinetics by means of ion concentration, whereas second-generation DASAs were less affected. Importantly, these results show how the previously reported concentration dependence of DASAs is not universal, and that DASAs with a more hybrid structure in the open form can achieve photoswitching at high concentrations. 相似文献