Ruchatz D, Fink G
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
Macromolecules. 1998 Jul 28;31(15):4674-80. doi: 10.1021/ma971042j.
The kinetics of ethene-norbornene copolymerizations using the metallocenes iPr[(3-R-Cp)Ind]ZrCl2 (with R = methyl or tert-butyl), MeCH[Cp]2ZrCl2, iPr[(3-R-Cp)Flu]ZrCl2 (with R = H, methyl, isopropyl, or tert-butyl), and Me2Si[(3-tert-butyl-Cp)Flu]ZrCl2 and half-sandwich catalysts Me2Si[Me4CpNtBu]TiCl2, Me2Si[Me4CpNtBu]ZrCl2, Me2Si[FluNtBu]ZrCl2, R-(+)-Me2Si[Me4CpNCH(CH3)-1-naphthyl]TiCl2, and C2H4[Me4CpNMe2]Cr(eta1,eta1-C4H8) together with methylaluminoxane as cocatalyst, have been investigated at 70 degreesC in a concentrated solution of norbornene in toluene and under an ethene pressure ranging from 4 to 60 bar (58-870 psi). The ethene reaction rates were measured during the copolymerization process at various ethene concentrations and the ethene reaction orders were determined. In some cases fractional ethene reaction orders higher than 1 were found, indicating a complex mechanism. The microstructure of the copolymers were analyzed by 13C NMR spectroscopy. The highest norbornene contents were achieved using metallocenes with sterically less demanding ligands such as MeCH[Cp]2ZrCl2. Unexpectedly, low norbornene contents (<50 mol %) were achieved with the half-sandwich catalysts. Depending on the catalyst structure, the microstructure of the copolymers consists of mainly isolated norbornene units, alternating monomer sequences or short norbornene microblocks with a maximum length of two or three. Additionally, the tacticity of the norbornene microblocks could be controlled by the catalyst structure. A mechanistic model, based on chain migratory insertion, is presented to explain the different copolymer structures through nonbonding steric interactions between monomer, growing polymer chain, and ligand system. On the basis of this model, penultimate effects (Markov statistic second order) caused by the last two inserted monomer units can be assumed.
使用茂金属iPr[(3-R-Cp)Ind]ZrCl2（R = 甲基或叔丁基）、MeCH[Cp]2ZrCl2、iPr[(3-R-Cp)Flu]ZrCl2（R = H、甲基、异丙基或叔丁基）以及Me2Si[(3-叔丁基-Cp)Flu]ZrCl2和半夹心催化剂Me2Si[Me4CpNtBu]TiCl2、Me2Si[Me4CpNtBu]ZrCl2、Me2Si[FluNtBu]ZrCl2、R-(+)-Me2Si[Me4CpNCH(CH3)-1-萘基]TiCl2和C2H4[Me4CpNMe2]Cr(η1,η1-C4H8)与甲基铝氧烷作为助催化剂，在70℃下于甲苯中降冰片烯的浓溶液中以及4至60巴（58 - 870磅力/平方英寸）的乙烯压力下研究了乙烯 - 降冰片烯共聚反应动力学。在共聚过程中，于不同乙烯浓度下测量乙烯反应速率并确定乙烯反应级数。在某些情况下，发现乙烯反应级数高于1的分数值，表明存在复杂的机理。通过13C NMR光谱分析共聚物的微观结构。使用具有空间位阻较小配体的茂金属（如MeCH[Cp]2ZrCl2）可实现最高的降冰片烯含量。出乎意料的是，半夹心催化剂实现了低降冰片烯含量（<50摩尔%）。根据催化剂结构，共聚物的微观结构主要由孤立的降冰片烯单元、交替的单体序列或最长为两三个的短降冰片烯微嵌段组成。此外，降冰片烯微嵌段的立构规整度可由催化剂结构控制。提出了一种基于链迁移插入的机理模型，以通过单体、增长的聚合物链和配体体系之间的非键空间相互作用来解释不同的共聚物结构。基于该模型，可以假定由最后两个插入的单体单元引起的倒数第二个效应（马尔可夫统计二阶）。
