氮配位单茂金属烯烃聚合催化剂

本文综述了近些年来以含氮基团为阴离子配体的单茂金属化合物作为烯烃精确聚合的催化剂的研究。氮配位单茂金属催化剂在烯烃聚合中显示出独特的特性,特别是对于乙烯的共聚合,不仅能得到Ziegler-Natta催化剂和传统茂金属催化剂不能合成的新的共聚物,还有优于其他单茂金属催化剂的共聚活性。环戊二烯基和含氮阴离子配体的改性是所得催化剂聚合效果的关键。本文涉及了乙烯均聚以及乙烯与α-烯烃(己烯-1、辛烯-1等)、苯乙烯和环烯烃(降冰片烯、四环十二碳烯等)的共聚合。     

杯[4]芳烃钛-Al(iBu)_3催化乙烯聚合

众所周知 ,茂金属催化剂用于烯烃聚合 ,不仅具有高的催化活性 ,而且能制得高规整度聚合物 ,在理论研究和工业应用中都有十分重要的意义 ,国际上已形成对茂金属催化剂的研究热潮 .人们在致力于研究茂金属催化剂的同时 ,并没有停止对非茂金属均相催化剂的研究 ,其中酚氧基钛、锆配合物的优良催化性能尤为引人注目 ,这类新型均相催化剂能高效地催化烯烃均聚[1 ] ,苯乙烯间规聚合[2 ] ,乙烯 苯乙烯共聚等[3] .杯芳烃是由若干个对叔丁基苯酚通过亚甲基经 2 ,6位连接而成的一类环状大分子 ,其结构与酚氧类配体相似 .李勇等曾发现杯芳烃钛化合物与…     

含8-羟基喹啉类配体的新型钛配合物[O,N]CpTiCl2的合成及其催化乙烯聚合研究

茂金属催化烯烃聚合的活性中心被认为是14电子结构的金属阳离子配合物[Cp2MR] +(R为烷基 ),并且金属中心的Lewis酸性和周围茂配体的空间构型对其催化活性及聚合产物的结构有直接的影响[1,2].然而,茂金属须大量MAO存在下才能显示高活性,并且其稳定性较差,这都一定程度上限制了茂金属催化剂的实际应用.近几年来,将含非环戊二烯基配体的金属配合物应用于烯烃均相聚合的研究大量出现[3],其中非环戊二烯基配体有含氮化合物 [4～9]和含氧化合物[10～15]等,这些非茂配合物可催化乙烯或丙烯聚合,但活性一般较低 .     

含8—羟基喹啉类配体的新型钛配合物[O,N]CpTiCl2的合成及其催化乙烯聚合研究

茂金属催化烯烃聚合的活性中心被认为是14电子结构的金属阳离子配合物[Cp2MR] +(R为烷基 ),并且金属中心的Lewis酸性和周围茂配体的空间构型对其催化活性及聚合产物的结构有直接的影响[1,2].然而,茂金属须大量MAO存在下才能显示高活性,并且其稳定性较差,这都一定程度上限制了茂金属催化剂的实际应用.近几年来,将含非环戊二烯基配体的金属配合物应用于烯烃均相聚合的研究大量出现[3],其中非环戊二烯基配体有含氮化合物 [4～9]和含氧化合物[10～15]等,这些非茂配合物可催化乙烯或丙烯聚合,但活性一般较低 .     

含8-羟基喹啉类配体的新型钛配合物[O,N]CpTiCl_2的合成及其催化乙烯聚合研究

茂金属催化烯烃聚合的活性中心被认为是1 4电子结构的金属阳离子配合物 [Ｃｐ2 ＭＲ]+ (Ｒ为烷基 ) ,并且金属中心的Ｌｅｗｉｓ酸性和周围茂配体的空间构型对其催化活性及聚合产物的结构有直接的影响[1,2 ] .然而 ,茂金属须大量ＭＡＯ存在下才能显示高活性 ,并且其稳定性较差 ,这都一定程度上限制了茂金属催化剂的实际应用 .近几年来 ,将含非环戊二烯基配体的金属配合物应用于烯烃均相聚合的研究大量出现[3] ,其中非环戊二烯基配体有含氮化合物[4～ 9] 和含氧化合物[10～ 15] 等 ,这些非茂配合物可催化乙烯或丙烯聚合 ,但活性一般较低 .茂金…     

原位反应法制备CpTi(dbm)Cl2/MgCl2载体型催化剂及其催化乙烯聚合的研究

非茂催化剂对烯烃聚合显示出优异的催化特性,是继ziegler—Natta催化剂及茂金属催化剂之后的新一代烯烃聚合催化剂^[1],其中非环戊二烯基配体有含氮化合物[2-8]和含氧化合物^[9-15]等,这些非茂配合物可催化乙烯或丙烯聚合．将金属中心与一个环戊二烯基和一个非环戊二烯基配体而     

同核双金属烯烃聚合催化剂

与单核金属配合物催化剂相比,双核金属配合物催化剂所具的双金属活性中心对烯烃聚合催化活性和所得聚合物的性能(包括聚合物微结构、分子量大小和分子量分布)产生了重要影响。本文综述了双金属配合物作为均相催化剂催化乙烯聚合及共聚合的最新研究,归纳思路包括不同的金属类型,即基于前过渡金属(Zr, Ti, Hf) 和后过渡金属(Ni, Fe, Co) 的双核金属组合; 不同的配体化合物,即CGC配体、酚氧亚胺配体、氮杂环胺配体、α-二亚胺和亚胺吡啶配体等。这些研究表明,前过渡金属催化剂不仅解决了乙烯自聚还实现了乙烯与α-烯烃共聚;后过渡金属催化剂高效催化乙烯自聚合,其中铁和钴催化剂获得高度线性聚乙烯,镍催化剂则产生多支链聚乙烯。     

第ⅣB族非茂金属烯烃聚合催化剂

烯烃聚合催化剂技术的发展关系着聚烯烃工业的命脉,而第ⅣB族非茂金属烯烃聚合催化剂作为目前催化剂研究的热点之一,不仅具有催化活性高、共聚单体范围广以及聚合物结构可控等优点,并且相比于茂金属催化剂而言,合成简单、成本低廉,有利于丰富烯烃聚合催化剂的种类和开发新型聚烯烃产品。本文按照配体的价齿类型综述了近十年来第ⅣB族非茂金属烯烃聚合催化剂的结构特点,及其在烯烃均聚和共聚反应中的催化性能,讨论了配体的电子效应和位阻效应对于配合物催化活性以及所得聚合物的结构、分子量等性质的影响,并对相关领域的未来发展提出了建议。     

烯烃高效催化剂及聚合与共聚合的研究

为中山大学高分子研究所烯烃配位聚合研究室在高效Ziegler-Natta催化剂、茂金属催化剂烯烃聚合与共聚合方面部分研究工作的概述。重点叙述了催化剂的设计、过渡金属配合物配体结构及聚合条件对乙烯、丙烯、1-丁烯、丁二烯、苯乙烯等烯烃单体聚合及共聚合活性以及聚合产物结构和分子量的影响。     

过渡金属络合物催化乙烯齐聚

综述了乙烯齐聚的最新成果,重点阐述了用于乙烯齐聚的新型催化剂,讨论了烯烃高聚与齐聚催化剂的关系,烯烃高聚与齐聚的反应机理相同,。差别主要在于烯烃插入与β－H消除反应的速率,第IV副族金属络合物主要催化乙烯齐聚,第Ⅲ副族金属主要催化乙烯高聚,改变茂金属催化体系的助催化剂和反应条件可得到齐聚产物,选择体积较小配体的第Ⅷ族金属络合物,有利于β－H消除得到齐聚产物。     

Olefin Polymerization Catalyzed by Double‐Decker Dipalladium Complexes: Low Branched Poly(α‐Olefin)s by Selective Insertion of the Monomer Molecule

Dipalladium complexes of a cyclic bis(diimine) ligand with a double‐decker structure catalyze polymerization of ethylene and α‐olefins and copolymerization of ethylene with 1‐hexene. The polymerization of 1‐hexene yields a polymer that is mainly composed of the hexamethylene unit formed by 2,1‐insertion of the monomer into the palladium–carbon bond, followed by chain‐walking (6,1‐insertion). The polymerization of 4‐methyl‐1‐pentene proceeds by 2,1‐insertion with a selectivity of 92–97 %, and affords the polymer with methyl and 2‐methylhexyl branches. 2,1‐Insertion occurs selectively in all of the polymerization reactions of α‐olefins catalyzed by the dipalladium complexes. Ethylene polymerization with the catalyst at 100 °C lasts over 24 h, whereas the monopalladium–diimine catalyst loses its activity within 8 h at 60 °C. Polyethylene obtained by the dipalladium catalyst is less‐branched and has a higher molecular weight compared to that of the monopalladium catalyst under the same conditions. Copolymerization of ethylene with 1‐hexene affords solid products with melting points and molecular weights that vary depending on the polymerization time, suggesting formation of a block and/or gradient copolymer.     

A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst

A structurally characterized cationic chromium(III) alkyl featuring a bulky nacnac ligand catalyzes the polymerization of ethylene as well as the copolymerization of ethylene with alpha-olefins. This well-characterized homogeneous catalyst constitutes a structural as well as functional model of the widely used heterogeneous Phillips olefin polymerization catalyst.     

Recent Advances in Olefin Polymerization Using Binary Catalyst Systems

Several homogeneous and heterogeneous binary systems have been applied to olefin polymerization in order to produce polymers with improved physical and/or chemical characteristics. This article reviews the recent developments in this area focusing mainly on polymer properties, the relationship between the types of catalyst present in the binary systems, their use in the homopolymerization of ethylene and propene, and the copolymerization of ethylene and higher α‐olefins.     

Modification of polyolefins as a modern strategy to designing polyolefin materials with a new complex of properties

Experimental data on multistage catalytic olefin polymerization processes are generalized. Such processes as the sequential homo-and copolymerization of ethylene and α-olefins; the copolymerization of ethylene and a cyclic monomer followed by postpolymerization polymer-analogous transformations via the ozonolysis of side vinylidene bonds; and the preparation of multilayer polyolefin compositions by polymerization filling make it possible to control the composition, molecular mass characteristics, supramolecular structure, and properties of polyolefins. The kinetic features of the sequential polymerization of olefins, namely, the monomer effect and the absence of the influence of the preliminary polymerization stage on the composition and molecular mass characteristics of polymer products isolated at subsequent stages, are examined. The mutual influence of components of multiphase polymer systems on the morphology and mechanical characteristics of final products is established.     

POLYKETONE FROM ETHYLENE WITH CARBON MONOXIDE CATALYZED BY NOVEL CATALYST SYSTEMS BASED ON COPPER WITH BIDENTATE PHOSPHORUS CHELATING LIGANDS

Copolymerization of ethylene with carbon monoxide was pertormed with Cu catalyst systems. Novel catalystsystems based on Cu (Cu(CH_3COO)_2/ligand/acid) were firstly reported for the copolymerization of ethylene with carbonmonoxide, in which the ligand was a bidentate phosphorus chelating ligand. The experimental results showed that this kindof Cu catalyst system exhibited high activity. When DPPP (1, 3-bis(diphenylphosphine)propane) and CH_3COOH were usedas ligand and acid, the corresponding catalyst system had the best activity of 108.1 g copolymer/(gCu·h). The novel Cu catalyst system had the advantages of high stability and low cost.     

Progress in Bimodal Polyethylene Produced by Metallocene Catalyst

The external new ways, kinds and recant advances of bimodal Polyethylene produced by metallocene catalyst were reviewed. For example, U.S.Pat.No 4939217 discloses an olefin polymerization supported catalyst comprising at least two different metallocenes each having different olefin polymerization termination rate constants in the presence of hydrogen. U.S.Pat. No.5077255 discloses an olefin polymerization supported catalyst comprising at least one metallocene of a metal, a non-metallocene transition metal and an alumoxane. The supported product is highly useful for the polymerization of olefins especially ethylene and especially for the copolymerization of ethylene and other mono and diolefins. U.S.Pat.No.5986024 discloses a process is provided for preparing polymer compositions which are multimodal in nature. The process involves contacting, under polymerization conditions, a selected addition polymerizable monomer with a metallocene catalyst having two or more distinct and chemically different active sites, and a catalyst activator.     

Influence of Polyethylene Glycol Unit on Palladium‐ and Nickel‐Catalyzed Ethylene Polymerization and Copolymerization

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.     

Synthesis of polycarbosilanes having a five‐membered cyclic carbonate structure and their application to prepare gel polymer electrolytes for lithium ion batteries

A silacyclobutane having a five‐membered cyclic carbonate structure (SBMC) was prepared, and its transition metal‐catalyzed ring‐opening polymerization at the four‐membered carbosilane unit was investigated as well as formation of carbosilane networked polymers and polymer gel electrolytes. The SBMC was synthesized by epoxidation of 1‐(4‐butenyl)‐1‐methylsilacyclobutane followed by insertion of CO₂ to the epoxide. Ring‐opening polymerization of the silacyclobutane moiety in the SBMC readily proceeded by a transition metal catalyst such as platinum divinyltetramethyldisiloxane complex. A flexible networked polymer film was obtained by copolymerization of the SBMC with a small amount of crosslinker, hexamethylene‐1,6‐bis(1‐methylsilacyclobutane) (HMBS). The copolymerization of SBMC and HMBS in 1 M LiPF₆ solution in ethylene carbonate and diethyl carbonate (3/7 v/v) gave a gel polymer electrolyte, which showed good ionic conductivity and could be applied to lithium ion batteries. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

This article discusses the similarities and differences between active centers in propylene and ethylene polymerization reactions over the same Ti‐based catalysts. These correlations were examined by comparing the polymerization kinetics of both monomers over two different Ti‐based catalyst systems, δ‐TiCl₃‐AlEt₃ and TiCl₄/DBP/MgCl₂‐AlEt₃/PhSi(OEt)₃, by comparing the molecular weight distributions of respective polymers, in consecutive ethylene/propylene and propylene/ethylene homopolymerization reactions, and by examining the IR spectra of “impact‐resistant” polypropylene (a mixture of isotactic polypropylene and an ethylene/propylene copolymer). The results of these experiments indicated that Ti‐based catalysts contain two families of active centers. The centers of the first family, which are relatively unstable kinetically, are capable of polymerizing and copolymerizing all olefins. This family includes from four to six populations of centers that differ in their stereospecificity, average molecular weights of polymer molecules they produce, and in the values of reactivity ratios in olefin copolymerization reactions. The centers of the second family (two populations of centers) efficiently polymerize only ethylene. They do not homopolymerize α‐olefins and, if used in ethylene/α‐olefin copolymerization reactions, incorporate α‐olefin molecules very poorly. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1745–1758, 2003     

Binuclear titanium complexes coordinated by rigid p-phenylene linked bis-β-carbonylenamine: Synthesis,structure, ethylene polymerization and copolymerization with 1,5-hexadiene

Binuclear complexes for olefin polymerization have attracted great attention due to their unique catalytic properties compared with their mononuclear counterparts. Here a series of p-phenylene-bridgedbis-β-carbonylenamine ligands and their binuclear Ti complexes Ti ₂ L ¹ – Ti ₂ L ³ were prepared and characterized by ¹H NMR, ¹³C NMR, Fourier transform infrared spectroscopy, and elemental analysis. The binuclear complex Ti ₂ L ³ bearing an octylthio sidearm was further investigated by single-crystalX-ray diffraction, which revealed that the ligand was of β-imino enol form, with one titanium atom ligated with six other atoms, forming a deformed octahedral configuration. Furthermore, the ligand in Ti ₂ L ³ adopted a cis configuration, which was different from the trans configuration of its m-phenylene-bridged derivatives. These binuclear complexes ( Ti ₂ L ¹ – Ti ₂ L ³ ) could catalyze ethylene polymerization and copolymerization with 1,5-hexadiene(1,5-HD) efficiently under modified methylaluminoxane activation. Compared with the mononuclear complex TiL ⁵ , the binuclear catalysts were thermally more stable and showed higher activity for ethylene polymerization at higher temperatures. The activity of these titanium complexes for the copolymerization of ethylene with 1,5-HD were over 10⁶ g/mol Ti.h.atm, almost twice as high as for homopolymerization. Compared with the mononuclear analogue TiL ⁵ and the m-substituted binuclear derivative Ti ₂ L ⁴ , binuclear catalyst Ti ₂ L ² showed higher activity and insertion rate of the comonomer. The activity of Ti ₂ L ² was two to three times higher than that of TiL ⁵ and Ti ₂ L ⁴ , indicating that p-substituted binuclear catalysts generate clear bimetallic synergistic effect for the copolymerization of ethylene and 1,5-HD. Meanwhile, 1,5-HD takes 1,3-cyclopentyl form in the polymer by 1,3-insertion. The copolymer prepared by binuclear catalysts had higher molecular weight and wider molecular weight distribution than that prepared by the mononuclear catalyst.