Polymerization with TMA-protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing α-diimine-type ligands

α-Diimine Ni complexes (7, 8) were used as catalyst precursors with MAO in co- and terpolymerization of ethylene/propylene/α-olefins with OH and COOH functional groups. Trimethylaluminium was used to protect the functional group of polar monomers. The presence of 5-hexen-1-ol seems to have no effect on the polymerization rate at all for the N,N′-bis(2,6-diisopropylphenyl) derivative 8 but caused activity decreases of about fivefold in copolymerization and around two times in terpolymerization for the N,N-dimesityl derivative 7. The effect levels off at higher polar comonomer concentration. This system, (7)/MAO, also incorporates well both 10-undecen-1-ol and 10-undecen-1-oic acid. The activities obtained with these α-diimine Ni complexes in co- and terpolymerization are three to twenty times higher than those obtained with group 4 Cp based complexes especially at concentrations of polar monomer in the feed higher than 80 mM. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2471–2480, 1999     

二醚型 Ziegler-Natta 催化剂催化丙烯与极性单体共聚

 以三乙基铝 (TEA) 为保护剂, 研究了 TiCl4/MgCl2/芴二醚/Al(C2H5)3 体系催化丙烯与十一烯醇或十一烯酸的共聚反应. 结果表明, 在极性单体存在下, 聚合反应活性随极性单体加入量的增加而降低, 但可保持丙烯均聚活性的一半以上, 反应活性衰减较小. 同时, 随着极性单体加入量的增加, 极性单体在共聚物中的含量增加. 与十一烯酸相比, 十一烯醇共聚具有更高的共聚活性和共单体含量. 随着共聚物中极性单体含量的增加, 聚合物的熔点和结晶温度都有所降低. 反应温度对丙烯和十一烯醇共聚的反应活性和共单体含量影响较小.     

Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments

The control of hydroxylated polyethylene (PE) structures was investigated in the copolymerization of ethylene with allyl alcohol or 10-undecen-1-ol with a specific metallocene, methylaluminoxane, and trialkyl aluminum catalyst system through changes in the copolymerization conditions. The incorporation of allyl alcohol into the PE backbones was controllable through changes in the trialkyl aluminum, leading to terminally hydroxylated PE or a copolymer possessing hydroxyalkyl side chains. The copolymerization of ethylene with 10-undecen-1-ol gave copolymers with hydroxyalkyl side chains of various contents with a variety of molecular weights through changes in the copolymerization conditions. The obtained copolymers were useful as macroinitiators that allowed polar polymer segments to grow on the PE backbones, leading to the creation of graft copolymers that possessed PE and polar polymer segments. In this way, polyethylene-g-poly(propylene glycol) (PE-g-PPG) and polyethylene-g-poly(ϵ-caprolactone) (PE-g-PCL) were synthesized. The ¹³C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization, and transmission electron microscopy demonstrated nanoorder phase separation and indistinct phase boundaries. ¹³C NMR and gel permeation chromatography analyses indicated the formation of PE-g-PCL, in which 36–80 mol % of the hydroxyl groups worked as initiators for ϵ-caprolactone polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3657–3666, 2003     

Well-defined vanadium complexes as the catalysts for olefin polymerization

The design and synthesis of well-defined vanadium complexes as efficient catalysts for olefin polymerization remains an attractive project for organometallic and polymeric research. Recently, vanadium complexes with well-defined structures have been explored for olefin (co)polymerization by several groups around the world. This article summarizes our recent progress in well-defined vanadium complexes bearing a variety of chelating β-enaminoketonato, salicylaldiminato, iminopyrrolide and tetradentate amine trihydroxy ligands, and their applications in ethylene polymerization, ethylene/α-olefin copolymerization and ethylene/cycloolefin copolymerization. The application of the optimized catalysts in the copolymerization of ethylene and polar monomer such as 3-buten-1-ol, 5-hexen-1-ol, 10-undecen-1-ol and 5-norbornene-2-methanol is also discussed. Particular attention has been paid to the relationships between the catalytic behavior and the electronic and geometrical structure of the precatalyst.     

Ethylene copolymers with Fischer-Tropsch olefins

The properties of ethylene copolymers, terpolymers and multipolymers prepared with even and uneven carbon number linear and branched α-olefins were compared. The most likely microstructures of ethylene/linear α-olefin copolymers was assigned by considering co-unit bulkiness, average crystallizable sequence lengths and thermal properties. The higher α-olefins were found to be more effective at decreasing density, but peak melting temperatures were higher. In terpolymers where lower α-olefins such as 1-butene and 1-pentene were used as comonomers, density was decreased more than the mathematical average expected from the ratio of comonomers in the terpolymers. Peak melting temperatures were also lower. Based on NMR evidence and the microstructures of the different copolymers the rationale for this occurrence could be ascribed to decreased clustering for these terpolymers. Branched α-olefins produced ethylene co- and terpolymers with significantly decreased densities as compared to the linear α-olefins. Impact strength of these polymers was also substantially higher, even at low comonomer content. Thermal evidence indicates that the microstructure of the co- and terpolymers containing branched α-olefins are very similar to that of the copolymers prepared with linear α-olefins of the same carbon number.     

以丙烯为主体的二元及三元共聚研究──丙烯与乙烯和丁烯－1的共聚合

研究了ＭｇＣｌ２载体高效催化剂用于丙烯为主体的与乙烯和丁烯－１的二元及三元共聚合反应：选择了最佳的共聚合条件；实验测定了共聚单体配比对共聚合活性、共聚物分子量和物理性能的影响；并用１３Ｃ—ＮＭＲ分析了共聚物组成、序列分布和支链结构等微观结构信息．     

Synthesis and Mechanical Properties of Polypropylene-based Polymer Hybrids via Controlled Radical Polymerization

Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.     

Radiation-induced terpolymerization of methyl α,β,β-trifluoroacrylate with tetrafluoroethylene and α-olefin

Radiation-induced terpolymerizations of methyl α,β,β-trifluoroacrylate (MTFA) with tetrafluoroethylene (TFE) and α-olefins, such as ethylene, propylene, and isobutylene, were carried out in bulk at 25°C for the purpose of controlling the content of ester group in the MTFA-α-olefin alternating copolymers. These monomers polymerized to form alternating terpolymers which contained 50 mole % α-olefin in a wide range of monomer composition. The content of MTFA, namely, the ester group in polymer, can be varied without destruction of the alternating structures between fluoroolefins (MTFA, TFE) and α-olefin by changing the MTFA/TFE ratio in the monomer mixture. The relative reactivities of MTFA and TFE in the terpolymerization were discussed according to kinetic treatments by free propagating and complex mechanisms. The relation between the MTFA/TFE ratio in the monomer mixture and that in terpolymer was explained favourbly by the complex mechanism. It was also concluded that the relative reactivity of MTFA is larger than that of TFE in the terpolymerizations.     

Compatibilization of polyethylene/polyamide 6 blends with functionalized polyethylenes prepared with metallocene catalyst

Metallocene catalyst technology was utilized to prepare functionalized polyethylenes, which were used as compatibilizers in polyethylene/polyamide 6 (40/60) blends. Polymerization of ethylene with 10-undecen-1-ol, 10-undecenoic acid, or N-methyl-10-undecenylamine resulted in ethylene copolymers with a small amount (0.2–1.2 mol %) of functionalized side chains. The blends were prepared in a twin-screw midiextruder, and injection molded with a mini-injection molding machine. The effect of the new compatibilizers on morphology and mechanical and thermal properties was studied. Toughness as well as stiffness and strength increased significantly with an addition of 10 wt % compatibilizer. Morphology became much more uniform, and crystallization and melting behavior changed. The Molau test with FTIR analysis was used to determine that the desired reactions between the compatibilizer and polyamide had actually taken place. The results showed functionalized polyethylenes prepared with metallocene catalysts to act as effective compatibilizers in polyethylene/polyamide 6 blends. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3099–3108, 1999     

13C NMR Study of Ethylene/propylene/octene-1Terpolymers Synthesized with TiCl4/MgCl2/I-Bu3Al as the Catalyst

Introduction　　 Various ethylene/ α- olefin copolymers such as LLDPE,VLDPE/ ULDPE,EPR,EPDMetc.have a wide application in polymer materials science and engineering.The properties ofthose copolymers are greatly influenced by the type,content and distributions of thecomonomer branches.The effects of different kinds of chain branches,which were derivedfrom comonomerincorporationsin themain chain of the ethylene/α- olefin copolymers on theirproperties and studied by many authors,have sh…     

Ethylene polymerization and copolymerization with 10‐undecen‐1‐ol using the catalyst system DADNi(NCS)2/MAO

The catalyst DADNi(NCS)₂ (DAD = (ArN?C(Me)? C(Me)?ArN); Ar = 2,6‐C₆H₃), activated by methylaluminoxane, was tested in ethylene polymerization at temperatures above 25 °C and variable Al/Ni ratio. The system was shown to be active even at 80 °C and when supported on silica. However, catalyst activity decreased. The catalyst system was also tested in ethylene and 10‐undecen‐1‐ol copolymerization at different ethylene pressures. The best activities were obtained at low polar monomer concentration (0.017 mol/L), using triisopropylaluminum (Al‐i‐Pr₃) to protect the polar monomer. The incorporation of the comonomer increased with the increase of polar monomer concentration. According to ¹³C NMR analyses, all the resulting polyethylenes were highly branched and the polar monomer incorporation decreased as ethylene pressure increased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5199–5208, 2007     

Precise control of microstructure of functionalized polypropylene synthesized by the ansa‐zirconocene/ MAO catalysts

We inclusively investigated polymerization behavior and structure of copolymer in the copolymerization of propylene and alkylaluminum‐protected polar allyl monomers. The control of the arrangement of polar group in the copolymer was discussed. It was proved that the location of polar group could be controlled by zirconocene catalyst and a kind of polar monomer. The indenyl or the 2‐methylindenyl ligands of zirconocene were favored to produce end‐functionalized polymers. It was also found that the trimethylaluminum‐protected allylamine and triisobutylaluminum‐protected allylmercaptan had superior ability in the synthesis of end‐functionalized polypropylene. On the other hand, the 2‐methyl‐4‐phenylindenyl ligand produced the copolymers containing both the end‐polar unit and inner‐polar unit at the polymer chains. Terpolymerization of propylene, polar allyl monomer, and 5‐hexen‐1‐ol was also conducted. The NMR study of the terpolymer revealed that both the 5‐hexen‐1‐ol and the polar allyl monomer were incorporated into the polymer chain. It has also become apparent that the polar allyl monomer units predominantly occupied the chain end, while the 5‐hexen‐1‐ol units were located at the inner of main chain. Consequently, we have achieved the synthesis of functionalized polypropylene in which the arrangement of polar group was precisely controlled. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1738–1748, 2008     

Ethylene polymerization reactions with Ziegler–Natta catalysts. II. Ethylene polymerization reactions in the presence of deuterium

Ethylene polymerization reactions with many Ziegler–Natta catalysts exhibit several features which differentiate them from polymerization reactions of α-olefins: a relatively low ethylene reactivity, higher polymerization rates in the presence of α-olefins, a high reaction order with respect to ethylene concentration, and strong reversible rate depression in the presence of hydrogen. A detailed kinetic analysis of ethylene polymerization reactions (see ref. 1 ) provided the basis for a new reaction scheme which explains all these features by postulating the equilibrium formation of a Ti C₂H₅ species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. This mechanism predicts that the β-agostically stabilized Ti C₂H₅ groups can decompose in the β-hydride elimination reaction with expulsion of ethylene and the formation of a Ti H bond even in the absence of hydrogen in the reaction medium. If D₂ is used as a chain transfer agent instead of H₂, the mechanism predicts the formation of deuterated ethylene molecules, which copolymerize with protioethylene. To prove this prediction, several ethylene homopolymerization reactions were carried out with a supported Ziegler–Natta titanium-based catalyst in the presence of large amounts of D₂. Analysis of gaseous reaction products and polymers confirmed the formation of several types of deuterated ethylene molecules and protio/deuterioethylene copolymers, respectively. In contrast, a metallocene catalyst, Cp₂ZrCl₂ MAO, does not exhibit these kinetic features. In the presence of deuterium, it produces only DCH₂ CH₂ (CH₂ CH₂)_x CH₂ CH₂D molecules. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4273–4280, 1999     

直接共聚法制备功能化聚烯烃研究进展

从催化剂研究发展的角度概述了直接配位共聚法制备功能化聚烯烃的研究现状 ,重点讨论了催化剂的结构 ,主催化剂和助催化剂以及催化剂和极性基团之间的相互作用对直接功能化聚合反应的影响。     

Ethylene polymerization reactions with Ziegler–Natta catalysts. I. Ethylene polymerization kinetics and kinetic mechanism

Kinetics of ethylene homopolymerization reactions and ethylene/1-hexene copolymerization reactions using a supported Ziegler–Natta catalyst was carried out over a broad range of reaction conditions. The kinetic data were analyzed using a concept of multicenter catalysis with different centers that respond differently to changes in reaction parameters. The catalyst contains five types of active centers that differ in the molecular weights of material they produce and in their copolymerization ability. In ethylene homopolymerization reactions, each active center has a high reaction order with respect to ethylene concentration, close to the second order. In ethylene/α-olefin copolymerization reactions, the centers that have poor copolymerization ability retain this high reaction order, whereas the centers that have good copolymerization ability change the reaction order to the first order. Hydrogen depresses activity of each type of center in the homopolymerization reactions in a reversible manner; however, the centers that copolymerize ethylene and α-olefins well are not depressed if an α-olefin is present in the reaction medium. Introduction of an α-olefin significantly increases activity of those centers, which are effective in copolymerizing it with ethylene but does not affect the centers that copolymerize ethylene and α-olefins poorly. To explain these kinetic features, a new reaction scheme is proposed. It is based on a hypothesis that the Ti—C₂H₅ bond in active centers has low reactivity due to the equilibrium formation of a Ti—C₂H₅ species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4255–4272, 1999     

Polymeric surfactants based on oleic acid. II. Copolymerization of sodium acrylamidostearate and 10-undecen-1-ol in a lamellar liquid crystal

Copolymerization of sodium acrylamidostearate (NaAAS) and 10-undecen-1-ol (UdOH) was performed in the lamellar liquid crystal (LLC) formed by NaAAS, UdOH, and water. After the polymerization the lamellar structure remained, and the disorder of the lamellar liquid crystal was, to some extent, reduced. Surface tension, small-angle X-ray diffraction, dynamic light scattering, viscosity, and fluorescence methods were used to study the properties of the copolymer. The polymeric surfactant behaves like polyelectrolyte and is more surface active than its precursor, i.e., NaAAS. The polymeric surfactant is capable of forming uni-molecular micelles through coiling of its hydrophobic chains. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2863–2872, 1999     

Effects of solvent as an electron-pair acceptor on propagation reactions during radical polymerization and copolymerization of polar vinyl monomers

We carried out radical homopolymerization and copolymerization in various kinds of solvents at 60°C by using diisopropyl fumarate (DiPF) and methyl methacrylate (MMA) as electron-accepting polar monomers and styrene (St) and vinyl benzoate (VB) as electron-donating monomers. The highest polymerization rate was observed in the polar and electron-pair accepting solvents, such as 2,2,2-trifluoroethanol for the homopolymerization and copolymerization of these monomers. It has been revealed that the polymerization rate is correlated to the electron-pair–accepting property of the solvent used, rather than the polarity in the linear free energy relationship. We have demonstrated the validity of the acceptor number as the index for interpreting the interaction of the solvent with the monomer and the propagating chain end. The monomer reactivity ratios were determined for the St–DiPF, VB–DiPF, and St–MMA copolymerizations. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2803–2814, 1999     

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     

Titanium ketimide complexes as α-olefin homo- and copolymerisation catalysts. X-ray diffraction structures of [TiCp(NCBu2)Cl2] (Cp=Ind, Cp*)

The synthesis of [TiInd(NC^tBu₂)Cl₂] and the applications of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*, Cp) as ethylene and propylene homopolymerisation catalysts, as well as its behaviour as catalysts of ethylene and 10-undecen-1-ol copolymerisation are described. The optimisation of the catalytic reactions showed that all compounds are very active homopolymerisation catalysts, particularly [TiInd(NC^tBu₂)Cl₂] that gives 123.37 × 10⁶ g/(molTi [E] h) and 50.77 × 10⁶ g/(molTi [P] h) of linear polyethylene and atatic polypropylene, respectively. The less active homopolymerisation catalyst, [TiCp(NC^tBu₂)Cl₂], is the most effective ethylene/10-undecen-1-ol copolymerisation catalyst, leading to the highest degree of polar monomer incorporation. The polymers obtained were characterised by NMR and DSC. The molecular structures of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*) were determined by X-ray diffraction studies.     

13Carbon nuclear magnetic resonance of ethylene–propylene–1‐hexene terpolymers

We report the complete ¹³C NMR characterization of a series of ethylene–propylene–1‐hexene terpolymers obtained with the metallocenic system rac‐ethylene bis‐indenyl zirconium dichloride, with different comonomer ratios. A detailed study of ¹³C NMR chemical shifts, triad sequence distributions, monomer‐average sequence lengths, and reactivity ratios for these terpolymers is presented. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2474–2482, 2004