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以Cs-对称芴基氨基二甲基钛络合物{[t-Bu NSi Me2Flu]Ti Me2}为催化剂,Ph3CB(C6H5)4为助催化剂,实现了降冰片烯与α-烯烃[己烯(2a)、辛烯(2b)、癸烯(2c)、十二烯(2d)和十八烯(2e)]的无规共聚,其中共聚物3e的结构经13C NMR确证。研究了2的侧链长度对3的共聚活性、热性能和光学性能的影响。结果表明,3a~3e均有较高的共聚活性,其值随着α-烯烃侧链长度和浓度的增加而提高,3e的共聚活性最高[63 100kg(polymer)·mol-1(Ti)·h-1];并具有高分子量(1.3×105~1.6×105)和窄分子量分布(1.10~1.48)以及可控的Tg(14℃~175℃)。3a~3e用甲苯通过涂膜法制得的自组装膜(3a'~3e')的透过率在90%左右,其中3e'的透过率高达96%。 相似文献
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使用廉价原料和简单工艺方法合成了芳氧钛类烯烃聚合和共聚催化剂,得到了(2-OMe C6H4O)Ti Cl3(C1),(2,4-Me2C6H3O)Ti Cl3(C2),Ti Cl3(1,4-OC6H4O)Ti Cl3(C3),Ti Cl3(1,4-OC6H2O-Me2-2,5)Ti Cl3(C4)以及相应的(Ar O)2Ti Cl2类络合物Ti Cl2(OC6H4-OMe-2)2(C5)和Ti Cl2(OC6H3-Me2-2,6)2(C6).通过1H NMR,13C NMR,MS以及元素分析进行了结构表征,确认了化学组成,以甲基铝氧烷(MAO)为助催化剂,Ar OTi Cl3/MAO体系显示了对乙烯聚合和共聚的高活性,13C NMR结果表明,聚合物中1-己烯插入率最高达6.88%(摩尔分数),而且得到的聚合物呈现高度支化,除了α-烯烃支链,还有甲基、乙基和长支链,并对其形成机理进行了研究,此外,对聚合温度、时间及共聚单体浓度对聚合反应的影响也进行了探讨. 相似文献
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最常用的Ziegler催化剂,是由IV—VIII族过渡元素的无机化合物与I—III族金属的有机化合物两个组分制成的。在此类催化剂存在下,于异相催化体系中,α-烯烃可以聚合成为全同立构(isotactic)聚合物,于均相催化系统内,自同一单体出发,则可得到间同立构(syadiotactic)高分子。一句话,能够促使α-烯烃定 相似文献
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刘伟 《理化检验(化学分册)》2008,44(2):134-136
采用对样品进行液氮淬火及溴化处理的制样方法,以期达到消除分子晶体场及分子链烯类端基对分析谱带的影响和干扰,结果表明:(1) 1 378 cm-1甲基对称变形振动谱带强而尖锐,和1 368 cm-1亚甲基面外摇摆振动谱带清晰分开,表明分子链上只存在一种单一的支链;(2)890 cm-1附近不存在表征长支链的甲基面内摇摆振动峰,只有772 cm-1附近存在表征乙基支链的亚甲基面内摇摆振动峰.成功地鉴定了以1-丁烯为共聚单体的线型低密度聚乙烯,方法简便、快速,为鉴定其他类的以烯烃为共聚单体的线型低密度聚乙烯(LLDPE)提供了重要思路. 相似文献
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1,1-二卤代-1-烯烃是有机化学中常见的合成片断,在合成化学中已得到了广泛的应用。该综述介绍了这一类化合物常见的制备方法以及反应的适用范围,并详细讨论了该类化合物在有机合成中的应用:(1)1,1-二卤代-1-烯烃在镁、有机锂、锌/溴化亚铜、二碘化钐、零价钯等金属或金属试剂作用下,发生α-消除反应生成烯基卡宾中间体的反应;(2)1,1-二卤代-1-烯烃在合成杂环以及核苷类似物等方面的应用。对于这类化合物在钯催化下的分子内(间)的偶联反应以及利用分子内的双环碳钯化反应,合成环状化合物等等方面的研究进展,也进行了详细的讨论。 相似文献
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Cyclopentadienyl-titanium complexes containing -OC6H4X ligands (X = Cl,CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the alpha-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett's factor (sigma).The chlorine atom is electron acceptor, while the methyl group is electron donor. These catalysts allow the preparation of polyethylene in a good yield. Propylene in the presence of the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25 degrees C under normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3)/MAO catalyst at 25 degrees gave mixtures with different contents of propylene dimers, trimers and tetramers. At 70 degrees C we obtained only propylene trimer.Using the catalysts with a -OC(6)H(4)Cl ligand we obtained atactic polymers with M(w) 182,000 g/mol (at 25 degrees C) and 100,000 g/mol (at 70 degrees C). The superior activity of the CpTiCl2(OC6H4Cl)/MAO catalyst used in polymerization of propylene prompted us to check its activity in polymerization of higher alpha-olefins (1-butene, 1-pentene, 1-hexene)and in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers were obtained. Gas chromatography analysis revealed the presence of dimers. The activity of the CpTiCl2(OC6H4Cl)/MAO catalyst in the co-polymerization of ethylene with higher alpha-olefins is limited by the length of the co-monomer carbon chain. Hence, the highest catalyst activities were observed in co-polymerization of ethylene with propylene (here a lower pressure of the reagents and shorter reaction time were applied to obtain catalytic activity similar to that for other co-monomers). For other co-monomers the activity of the catalyst decreases as follows: propylene >1-butene > 1-pentene > 1-hexene. In the case of co-polymerization of ethylene with propylene, besides an increase in catalytic activity, an increase in the average molecular weight M(w) of the polymer was observed. Other co- monomers used in this study caused a decrease of molecular weight. A significant increase in molecular weight distribution (M(w)/M(n)) evidences a great variety of polymer chains formed during the reaction. 相似文献
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S. Cesca G. Bertolini G. Santi P. V. Duranti 《Journal of polymer science. Part A, Polymer chemistry》1971,9(6):1575-1598
A detailed investigation of the terpolymerization reaction of ethylene and propylene with 1-isopropylidene-dicyclopentadiene (II) was carried out by empolying vanadiumbased anionic coordinate catalysts [preferentially V(Acac)3? AlEt2Cl]. The influence of some polymerization parameters, i.e., concentration of II, of the catalyst; polymerization time, etc., were particularly examined. The catalysts were found to be active in C2H4? II copolymerization also, but neither C3H6? II copolymer nor II homopolymer were obtained. By using the 5,6-dihydro derivative of II as comonomer, it was found through ultraviolet, infrared, and NMR analyses that the incorporation of II in polyethylene or ethylene–propylene chains took place randomly and by selective opening of the norbornene double bond. The quantitative determination of the unsaturation present in C2H4? C3H6? II terpolymer was studied by means of absorption of iodine halides and through a spectroscopic ultraviolet method. Reference was made to terpolymer samples containing 14C-labeled II. The content of II was generally less than 35 wt-% both in copolymer and in terpolymer prepared. The relatively high reactivity of II is discussed in terms of norbornene ring strain and compared with the reactivity of 1-isopropylidene-3a,4,7,7a-tetrahydroindene (I) previously reported. 相似文献
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Akella Sivaramakrishna Paul Mushonga Ian L. Rogers Feng Zheng Raymond J. Haines Ebbe Nordlander John R. Moss 《Polyhedron》2008,27(7):1911-1916
An efficient and selective isomerization of 1-alkenes to their corresponding 2-alkenes is achieved by using binary metal carbonyls such as Ru3(CO)12 as catalysts. Possible mechanisms are discussed. Substituents on the 1-alkene have a significant effect on the isomerization. 相似文献
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Fast scanning chip calorimetry has been employed to study the effect of the type and concentration of co-units on the rate
of mesophase formation and crystallization in random isotactic copolymers of propylene and 1-alkenes, including ethylene,
1-butene, 1-hexene, and 1-octene. The dependence of the rate of ordering on temperature of the propylene homopolymer shows
two distinct maxima around 300 and 340–350 K which are related to mesophase formation and crystallization, respectively. Addition
of 1-alkene co-units leads to a decrease of the maximum rate of both crystallization and mesophase formation. At comparable
temperature and molar percentage of co-units in the propylene chain, ethylene, and 1-butene co-units cause less reduction
of the maximum rate of ordering than 1-hexene or 1-octene co-units. The experimental observations are discussed in the context
of possible incorporation of these chain defects into the ordered structures. 相似文献
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《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1171-1180
Polymerization of ethylene and propylene with VCl4-BuLi (Bu = n-Bu, sec-Bu, tert-Bu) catalysts was investigated. The VCl4-BuLi catalysts were found to initiate the polymerization of ethylene and propylene. The VCl4-BuLi catalysts gave an ultra high molecular polyethylene. The effect of the Li /V mole ratio on the polymerization of ethylene with the VCl4-BuLi catalysts was observed, an the catalyst gave an optimum rate at the Li/V ratio of about 3.0. The polyethylene obtained with the VCl4-BuLi catalyst was found to be a linear structure. In the polymerization of propylene with the VCl4-BuLi catalyst, the polymers contain mm contents of 56–66% were produced. 相似文献
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L. A. Rishina Y. V. Kissin S. S. Lalayan V. G. Krasheninnikov E. O. Perepelitsina T. I. Medintseva 《Polymer Science Series B》2016,58(2):152-162
The polymerization of ethylene and propylene and the copolymerization of ethylene and hexene-1 with a Ti(O-iso-Pr)4–AlR2Cl/MgBu2 catalyst system have been studied. The advantages of this system over metallocene and postmetallocene catalysts are high activity, low cost, and ease of synthesis. The resulting polymers and copolymers are characterized by a broad molecular-mass distribution, which reflects the heterogeneity of the active sites with respect to kinetic parameters. As a consequence, the ethylene/hexene-1 copolymers exhibit compositional heterogeneity. The active sites of the system produce copolymers with a pronounced tendency toward alternation of monomer units. The propylene polymerization product is mostly amorphous atactic polypropylene. 相似文献
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E. Albizzati U. Giannini G. Balbontin I. Camurati J. C. Chadwick T. Dall'occo Y. Dubitsky M. Galimberti G. Morini A. Maldotti 《Journal of polymer science. Part A, Polymer chemistry》1997,35(13):2645-2652
The behavior in propylene polymerization of divalent titanium compounds of type [η6-areneTiAl2Cl8], both as such and supported on activated MgCl2, has been studied and compared to that of the simple catalyst MgCl2/TiCl4. Triethylaluminium was used as cocatalyst. The Ti–arene complexes were active both in the presence and in the absence of hydrogen, in contrast to earlier reports that divalent titanium species are active for ethylene but not for propylene polymerization. 13C-NMR analysis of low molecular weight polymer fractions indicated that the hydrogen activation effect observed for the MgCl2-supported catalysts should be ascribed to reactivation of 2,1-inserted (“dormant”) sites via chain transfer, rather than to (re)generation of active trivalent Ti via oxidative addition of hydrogen to divalent species. Decay in activity during polymerization was observed with both catalysts, indicating that for MgCl2/TiCl4 catalysts decay is not necessarily due to overreduction of Ti to the divalent state during polymerization. In ethylene polymerization both catalysts exhibited an acceleration rather than a decay profile. It is suggested that the observed decay in activity during propylene polymerization may be due to the formation of clustered species that are too hindered for propylene but that allow ethylene polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2645–2652, 1997 相似文献
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The article discusses recent results of kinetic analysis of propylene and ethylene polymerization reactions with several types
of Ti-based catalysts. All these catalysts, after activation with organoaluminum cocatalysts, contain from two to four types
of highly isospecific centers (which produce the bulk of the crystalline fraction of polypropylene) as well as several centers
of reduced isospecificity. The following subjects are discussed: the distribution of active centers with respect to isospecificity,
the effect of hydrogen on polymerization rates of propylene and ethylene, and similarities and differences between active
centers in propylene and ethylene polymerization reactions over the same catalysts. Ti-based catalysts contain two families
of active centers. The centers of the first family are capable of polymerizing and copolymerizing all α-olefins and ethylene.
The centers of the second family efficiently polymerize only ethylene. Differences in the kinetic effects of hydrogen and
α-olefins on polymerization reactions of ethylene and propylene can be rationalized using a single assumption that active
centers with alkyl groups containing methyl groups in the β-position with respect to the Ti atom, Ti-CH(CH3)R, are unusually unreactive in olefin insertion reactions. In the case of ethylene polymerization reactions, such an alkyl
group is the ethyl group (in the Ti-C2H5 moiety) and, in the case of propylene polymerization reactions, it is predominantly the isopropyl group in the Ti-CH(CH3)2 moiety.
Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 11, pp. 1911–1934.
The text was submitted by the authors in English. 相似文献
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Yury V. Kissin 《Journal of polymer science. Part A, Polymer chemistry》2003,41(12):1745-1758
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 相似文献