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1.
Jiazhen Chen Yanshan Gao Tobin J. Marks 《Angewandte Chemie (International ed. in English)》2020,59(35):14726-14735
Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentially upgrading polyolefins for advanced, value‐added applications. The metal catalyst‐mediated copolymerization of non‐polar olefins with polar comonomers represents the seemingly most straightforward, atom‐ and energy‐efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)‐catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, largely associated with the Lewis basicity of the polar co‐monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this Minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechanistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them. 相似文献
2.
《Macromolecular rapid communications》2017,38(19)
Ziegler–Natta catalysts have played a major role in industry for the polymerization of dienes and vinyl monomers. However, due to the deactivation of the catalyst, this system fails to polymerize polar vinyl monomers such as vinyl acetate, methyl methacrylate, and methyl acrylate. Herein, a catalytic system composed of NdCl3⋅3TEP/TIBA is reported, which promotes a quasi‐living polymerization of dienes and is also active for the homopolymerization of polar vinyl monomers. Additionally, this catalytic system generates polymyrcene‐b‐polyisoprene and poly(myrcene)‐b‐poly(methyl methacrylate) diblock copolymers by sequential monomer addition. To encourage the replacement of petroleum‐based polymers by environmentally benign biobased polymers, polymerization of β‐myrcene is demonstrated with a catalytic activity of ≈106 kg polymer mol Nd−1 h−1. 相似文献
3.
Xiaoqiang Hu Dr. Yixin Zhang Baixiang Li Prof. Dr. Zhongbao Jian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(46):11935-11942
Fluorine substituents in transition metal catalysts are of great importance in olefin polymerization catalysis; however, the comprehensive effect of fluorine substituents is elusive in seminal late transition metal α-diimine catalytic system. In this contribution, fluorine substituents at various positions (ortho-, meta-, and para-F) and with different numbers (Fn; n=0, 1, 2, 3, 5) were installed into the well-defined N-terphenyl amine and thus were studied for the first time in the nickel α-diimine promoted ethylene polymerization and copolymerization with polar monomers. The position of the fluorine substituent was particularly crucial in these polymerization reactions in terms of catalytic activity, polymer molecular weight, branching density, and incorporation of polar monomer, and thus a picture on the fluorine effect was given. As a notable result, the ortho-F substituted α-diimine nickel catalyst produced highly linear polyethylenes with an extremely high molecular weight (Mw=8703 kDa) and a significantly low degree of branching of 1.4/1000 C; however, the meta-F and/or para-F substituted α-diimine nickel catalysts generated highly branched (up to 80.2/1000 C) polyethylenes with significantly low molecular weights (Mw=20-50 kDa). 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(46):14864-14868
The transition‐metal‐catalyzed copolymerization of olefins with polar functionalized co‐monomers represents a major challenge in the field of olefin polymerization. It is extremely difficult to simultaneously achieve improvements in catalytic activity, polar monomer incorporation, and copolymer molecular weight through ligand modifications. Herein we introduce a polyethylene glycol unit to some phosphine‐sulfonate palladium and nickel catalysts, and its influence on ethylene polymerization and copolymerization is investigated. In ethylene polymerization, this strategy leads to enhanced activity, catalyst stability, and increased polyethylene molecular weight. In ethylene copolymerization with polar monomers, improvements in all copolymerization parameters are realized. This effect is most significant for polar monomers with hydrogen‐bond‐donating abilities. 相似文献
5.
Dr. Wasim Ullah Khan Hassam Mazhar Farrukh Shehzad Dr. Mamdouh A. Al-Harthi 《Chemical record (New York, N.Y.)》2023,23(3):e202200243
The synthesis of polar functionalized polyolefin (PFP) offers improvement in mixing properties, polymer surface, and rheological properties with the potential of upgraded polyolefins for modern and ingenious applications. The synthesis of PFP from metal-based catalyzed olefin (non-polar in nature) copolymerization with polar comonomers embodies energy-efficient, atom-efficient, and apparently an upfront methodology. Despite their outstanding success during conventional polymerization of olefin, 3rd and 4th group (early transition metal)-based catalysts, owing to their electrophilic nature, face challenges mainly due to Lewis basic sites of the polar monomers. On the contrary, late transition metal-based catalysts have also made progress, in recent years, for PFP synthesis. The recent past has also witnessed several advancements in the development of dominating palladium-based catalysts while their lower resistance towards ligand functional groups has limited the practical application of abundant and cheaper nickel-based catalysts. However, the relentless efforts of the scientific community, during the past half-decade, have indicated rigorous progress in the development of nickel-based catalysts for PFP synthesis. In this review, we have abridged the recent research trends in both early as well as late transition metal-based catalyst development. Furthermore, we have highlighted the role of transition metal-based catalysts in influencing the polymer properties. 相似文献
6.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(17):4790-4796
Supported metal nanocrystals have exhibited remarkable catalytic performance in hydrogen generation reactions, which is influenced and even determined by their supports. Accordingly, it is of fundamental importance to determine the direct relationship between catalytic performance and metal–support interactions. Herein, we provide a quantitative profile for exploring metal–support interactions by considering the highest occupied state in single‐atom catalysts. The catalyst studied consisted of isolated Rh atoms dispersed on the surface of VO2 nanorods. It was observed that the activation energy of ammonia–borane hydrolysis changed when the substrate underwent a phase transition. Mechanistic studies indicate that the catalytic performance depended directly on the highest occupied state of the single Rh atoms, which was determined by the band structure of the substrates. Other metal catalysts, even with non‐noble metals, that exhibited significant catalytic activity towards NH3BH3 hydrolysis were rationally designed by adjusting their highest occupied states. 相似文献
7.
Francesco Ciardelli Angelina Altomare Guillermo Arribas Giuseppe Conti Renato Colle 《先进技术聚合物》1995,6(3):159-167
Polymerization of olefins mediated by transition metal derivatives (Ziegler–Natta polymerization) is one of the most scientifically and industrially important processes of molecular conversion. Electron transfer mechanism could play a significant role in both heterogeneous and homogeneous catalysts. The catalytic activity strongly depends on the presence of two metallocene ligands attached to the transition metal (more commonly zirconium) which grants the valence form of zirconium in complexes of the type Cp2ZrX2(X=Cl or CH3) followed by the formation of the (Cp2ZrX)+ cation under the effect of a Lewis acid. On the other hand, Ti complexes with only one metallocene ligand give the syndiospecific polymerization of styrene, where the phenyl group appears to act as electron donor for the transition metal. The remarkable electronic effect of the metallocene groups in determining catalytic activity is demonstrated by the study of substituted metallocene ligands as well as other ligands around the metal. These effects cannot be, however, completely separated from steric effects which seem to be responsible for the impressive and versatile stereochemical control determined by symmetry properties of the transition metal complex. 相似文献
8.
Jiazhen Chen Alessandro Motta Binghao Wang Yanshan Gao Tobin J. Marks 《Angewandte Chemie (International ed. in English)》2019,58(21):7030-7034
In principal, the direct copolymerization of ethylene with polar comonomers should be the most efficient means to introduce functional groups into conventional polyolefins but remains a formidable challenge. Despite the tremendous advances in group 4‐centered catalysis for olefin polymerization, successful examples of ethylene + polar monomer copolymerization are rare, especially without Lewis acidic masking reagents. Here we report that certain group 4 catalysts are very effective for ethylene + CH2=CH(CH2)nNR2 copolymerizations with activities up to 3400 Kg copolymer mol?1‐Zr h‐1 atm‐1, and with comonomer enchainment up to 5.5 mol % in the absence of masking reagents. Group 4 catalyst‐amino‐olefin structure–activity‐selectivity relationships reflect the preference of olefin activation over free amine coordination, which is supported by mechanistic experiments and DFT analysis. These results illuminate poorly understood facets of d0 metal‐catalyzed polar olefin monomer copolymerization processes. 相似文献
9.
Jiazhen Chen Alessandro Motta Binghao Wang Yanshan Gao Tobin J. Marks 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7104-7108
In principal, the direct copolymerization of ethylene with polar comonomers should be the most efficient means to introduce functional groups into conventional polyolefins but remains a formidable challenge. Despite the tremendous advances in group 4‐centered catalysis for olefin polymerization, successful examples of ethylene + polar monomer copolymerization are rare, especially without Lewis acidic masking reagents. Here we report that certain group 4 catalysts are very effective for ethylene + CH2=CH(CH2)nNR2 copolymerizations with activities up to 3400 Kg copolymer mol?1‐Zr h‐1 atm‐1, and with comonomer enchainment up to 5.5 mol % in the absence of masking reagents. Group 4 catalyst‐amino‐olefin structure–activity‐selectivity relationships reflect the preference of olefin activation over free amine coordination, which is supported by mechanistic experiments and DFT analysis. These results illuminate poorly understood facets of d0 metal‐catalyzed polar olefin monomer copolymerization processes. 相似文献
10.
Martin G. Mayershofer Oskar Nuyken 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5723-5747
For many years, considerable research efforts have been dedicated to π‐conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition‐metal‐based initiating systems comprise not only simple transition‐metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single‐component systems such as transition‐metal alkylidene complexes. Extensive fine‐tuning of the electronic and steric properties of initiator–monomer systems eventually allowed the tailor‐made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill‐defined group 5 and 6 transition metal halide‐based initiators, well‐defined transition‐metal alkylidene complexes, and rhodium(I)‐based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723–5747, 2005 相似文献
11.
Presence versus Proximity: The Role of Pendant Amines in the Catalytic Hydrolysis of a Nerve Agent Simulant 下载免费PDF全文
Dr. Timur Islamoglu Dr. Manuel A. Ortuño Emmanuel Proussaloglou Dr. Ashlee J. Howarth Dr. Nicolaas A. Vermeulen Ahmet Atilgan Prof. Abdullah M. Asiri Prof. Christopher J. Cramer Prof. Omar K. Farha 《Angewandte Chemie (International ed. in English)》2018,57(7):1949-1953
Amino‐functionalized zirconium‐based metal‐organic frameworks (MOFs) have shown unprecedented catalytic activity compared to non‐functionalized analogues for hydrolysis of organophosphonate‐based toxic chemicals. Importantly, the effect of the amino group on the catalytic activity is significantly higher in the case of UiO‐66‐NH2, where the amino groups reside near the node, compared to UiO‐67‐m‐NH2, where they are directed away from the node. Herein, we show that the proximity of the amino group is crucial for fast catalytic activity towards hydrolysis of organophosphonate‐based nerve agents. The generality of the observed amine‐proximity‐dictated catalytic activity has been tested on two different MOF systems which have different topology. DFT calculations reveal that amino groups on all the MOFs studied are not acting as Brønsted bases; instead they control the microsolvation environment at the Zr6‐node active site and therefore increase the overall catalytic rates. 相似文献
12.
Xiaofan Zhang Shangtao Chen Huayi Li Zhicheng Zhang Yingying Lu Chunhong Wu Youliang Hu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(1):59-68
With triisobutylaluminum as a protection reagent, copolymerizations of ethylene with 10‐undecen‐1‐ol, 10‐undecenoic acid, and 5‐hexen‐1‐ol have been performed with bis[(3,5‐di‐tBu? C6H2? 2‐O)? PhC?N(2‐F? C6H4)]ZrCl2 ( a )/methylaluminoxane or bis[(3,5‐di‐tBu? C6H2? 2‐O)? PhC?N(2‐F? C6H4)]TiCl2 ( b )/methylaluminoxane as the catalyst. Both catalysts exhibit high activities of copolymerization in the presence of polar groups. The properties of the copolymers are strongly affected by the central metal properties of the catalysts. In comparison with complex a , titanium complex b appears to be less sensitive to polar monomers and more favorable for the preparation of higher molecular weight functionalized polyethylenes containing higher contents of polar groups. Studies on the polymerization temperature indicate that the catalytic activities decrease greatly with both complex a and complex b . The comonomer contents incorporated into the copolymers are slightly dependent on the polymerization temperature in the case of complex a , whereas in the case of complex b , the effect of the polymerization temperature is more distinct: an increase in the polymerization temperature can efficiently facilitate the incorporation of polar comonomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 59–68, 2007 相似文献
13.
14.
《Angewandte Chemie (International ed. in English)》2017,56(19):5170-5181
Unique features of earth‐abundant transition‐metal catalysts are reviewed in the context of catalytic carbon–carbon bond‐forming reactions. Aryl‐substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open‐shell iron and cobalt alkyl complexes have been synthesized that serve as single‐component olefin polymerization catalysts. Reduced bis(imino)pyridine iron and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Studies of the electronic structure support open‐shell intermediates, a deviation from traditional strong‐field organometallic compounds that promote catalytic C−C bond formation. 相似文献
15.
Polar vinyl polymers, a class of polymers with polar groups as side chains, have significant advantages over conventional nonpolar polyolefin materials in terms of viscosity, toughness, interfacial properties (dyeability and printability), and compatibility with solvents or other polymers. Among them, aromatic polar vinyl polymers are of interest because of their good heat resistance properties. In addition, stereoselective polymerization of aromatic polar vinyl monomers has been rapidly developed because the steric structure of the polymer has a significant impact on its physical properties. In this paper, we review the research progress of stereoselective polymerization catalysts for aromatic polar vinyl monomers in recent years, discuss in detail the influence of ligand structure, electronic effect of substituents, spatial site resistance effect, central rare earth metal species and polymerization solvents on the activity and stereoselectivity of polymerization reactions, and explore the possible mechanism of polymerization reaction. 相似文献
16.
Kai Chen Jia‐Long Ling Chuan‐De Wu 《Angewandte Chemie (International ed. in English)》2020,59(5):1925-1931
Heterostructural metal/metal oxides are the very promising substituents of noble‐metal catalysts; however, generation and further stabilization of accessible metal/metal oxide heterojunctions are very difficult. A strategy to encapsulate and stabilize Cu/Cu2O nanojunctions in porous organic frameworks in situ is developed by tuning the acrylate contents in copper‐based metal–organic frameworks (Cu‐MOFs) and the pyrolytic conditions. The acrylate groups play important roles on improving the polymerization degree of organic frameworks and generating and stabilizing highly dispersed and accessible Cu/Cu2O heteronanojunctions. As a result, pyrolysis of the MOF ZJU‐199, consisting of three acrylates per ligand, generates abundant heterostructural Cu/Cu2O discrete domains inside porous organic matrices at 350 °C, demonstrating excellent catalytic properties in liquid‐phase hydrogenation of furfural into furfuryl alcohol, which are much superior to the non‐noble metal‐based catalysts. 相似文献
17.
Yeong-Soon Gal Bal Jung Won-Chul Lee Sam-kwon Choi 《Journal of polymer science. Part A, Polymer chemistry》1992,30(12):2657-2662
Some polyacetylene derivatives containing an amine functional group were prepared by the polymerization of propargylamine (PA) and 1,1-diethylpropargylamine (DEPA) with various transition metal catalysts. In the polymerization of PA, Mo-based catalysts were more effective than that of W-based catalysts, and organoaluminum compounds, especially EtAlCl2, were found to be very effective cocatalysts. In the polymerization of DEPA, Mo-and W-based catalyst systems showed a similar catalytic activity. The polymerization easily proceeded in polar solvents such as nitrobenzene and DMF as well as nonpolar aromatic solvents such as chlorobenzene, toluene, etc. The resulting poly(PA) and poly(DEPA) were insoluble in organic solvents regardless of polymerization catalysts but the polymers were found to be stable to air oxidation. Thermogravimetric analyses and thermal transitions of poly(PA) and poly(DEPA) were also studied. © 1992 John Wiley & Sons, Inc. 相似文献
18.
Jürgen Schellenberg 《European Polymer Journal》2004,40(10):2259-2267
The syndiospecific polymerization of styrene with a new class of multinuclear transition metal catalysts in the presence of methylalumoxane and triisobutylaluminum has been investigated. The new multinuclear catalysts [(η5-C5Me5)Ti]4(μ-O)6 and [(η5-C13H17)Ti]4(μ-O)6 were received by reaction of the corresponding mononuclear compounds with water and characterized by X-ray crystal structure analysis. The molecular structure of both complexes is tetrameric with six bridging oxygen atoms between the four titanium atoms, forming an adamantane-like cage structure with a substituted cyclopentadienyl ligand remaining η5-bonded to each titanium atom.The bulky [(η5-C13H17)Ti]4(μ-O)6 shows higher polymerization conversions than [(η5-C5Me5)Ti]4(μ-O)6. The polymerization activity is significantly increased by an enhancement of the MAO concentration after a short retardation period and levels off at MAO/[(η5-C13H17)Ti]4(μ-O)6 molar ratios above about 600. Triisobutylaluminum increases the polymerization yield to a maximum at a TIBA/[(η5-C13H17)Ti]4(μ-O)6 molar ratio of about 30-100, but considerably decreases it at higher molar ratios below the polymerization conversion reached without any additional aluminum alkyl. Both compounds affect molecular weight and molecular weight distribution without any influence on the stereospecificity of the different catalytic sites active in polymerization reactions.The new multinuclear transition metal catalysts reach about 30-50% of the polymerization activity of the mononuclear catalysts on a molar basis and show a remarkably high catalytic activity in complex-coordinative polymerizations even after storage in non-inert-atmosphere conditions. The active polymerization sites of the multinuclear catalysts are not as uniform as the active sites of the mononuclear catalysts are and provide polystyrenes of a slightly lower syndiospecificity, but do not significantly influence the weight average molecular weights. 相似文献
19.
A Versatile Ligand Platform for Palladium‐ and Nickel‐Catalyzed Ethylene Copolymerization with Polar Monomers 下载免费PDF全文
The ability to carry out transition‐metal‐catalyzed copolymerizations of olefins with polar monomers is a great challenge in the field of olefin polymerization. Palladium has been the dominant player in this field, while its low‐cost nickel counterpart has only achieved very limited success. We report the synthesis and evaluation of a highly versatile platform based on diphosphazane monoxide ligands. Both palladium and nickel catalysts bearing these ligands mediate the copolymerization of ethylene with a number of fundamental polar monomers. 相似文献
20.
Shimrit Gendler Stanislav Groysman Zeev Goldschmidt Michael Shuster Moshe Kol 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1136-1146
The polymerization of the substituted olefins 4‐methylpentene and vinylcyclohexane by dibenzyl titanium and zirconium complexes of three amine bis(phenolate) ligands is reported. The ligands featured a dimethylamino side‐arm donor and either electron‐withdrawing (Cl and Br) or methyl phenolate substituents. After activation with B(C6F5)3, the zirconium catalysts exhibited a higher activity than the titanium catalysts toward these bulky olefins. Very high weight‐average molecular weight poly(4‐methylpentene) was obtained with the zirconium catalysts. The zirconium catalysts were employed in 1‐hexene polymerization, and their activity was found to be the highest ever reported for catalysts of the amine bis(phenolate) family. The catalysts featuring methyl phenolate substituents showed a higher activity toward these substituted olefins than the electron‐poor catalysts; this trend was opposite to their activity toward 1‐hexene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1136–1146, 2006 相似文献