Preparation of linear α‐olefins to high‐molecular weight polyethylenes using cationic α‐diimine nickel(II) complexes containing chloro‐substituted ligands

A series of α‐diimine nickel(II) complexes containing chloro‐substituted ligands, [(Ar)N?C(C₁₀H₆)C?N(Ar)]NiBr₂ ( 4a , Ar = 2,3‐C₆H₃Cl₂; 4b , Ar = 2,4‐C₆H₃Cl₂; 4c , Ar = 2,5‐C₆H₃Cl₂; 4d , Ar = 2,6‐C₆H₃Cl₂; 4e , Ar = 2,4,6‐C₆H₂Cl₃) and [(Ar)N?C(C₁₀H₆)C?N(Ar)]₂NiBr₂ ( 5a , Ar = 2,3‐C₆H₃Cl₂; 5b , Ar = 2,4‐C₆H₃Cl₂; 5c , Ar = 2,5‐C₆H₃Cl₂), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl‐substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear α‐olefins to high‐molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964–1974, 2006     

Direct synthesis of linear low‐density polyethylene of ethylene/1‐hexene from ethylene with a tandem catalytic system in a single reactor

Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η⁵‐C₅H₄CMe₂C₆H₅)TiCl₃ ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η⁵‐C₅Me₄)SiMe₂(^tBuN)]TiCl₂ ( 2 )/MMAO or rac‐Me₂Si(2‐MeBenz[e]Ind)₂ZrCl₂ ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004     

Synthesis of ultra‐high‐molecular‐weight ethylene‐propylene copolymer via quasi‐living copolymerization with N‐heterocyclic carbene ligated vanadium complexes

The quasi‐living copolymerization of ethylene with propylene was achieved by using N‐heterocyclic carbene (NHC) ligated vanadium complex ( V3 , VOCl₃[1,3‐(2,6‐ⁱPr₂C₆H₃)₂(NCH?)₂C:]) due to the stabilization of active center by the introduction of bulky and electron rich NHC ligand with bulky isopropyl substituents at the ortho positions of the phenyl rings. The weight‐average molecular weight (M_w) of the resulting copolymer increases linearly with its weight in 20 min. The ultra‐high‐molecular‐weight (UHMW) ethylene‐propylene copolymer (M_w = 1612 kg mol^?1) can be synthesized with V3 /Et₃Al₂Cl₃ catalytic system. The novel complex V4′ (VCl₃[1,3‐(2,4,6‐Me₃C₆H₂)₂(NCH?)₂C:]·2THF) was constructed by the introduction of two coordinated tetrahydrofuran molecules and decrease in steric hindrance at the ortho positions of phenyl rings. The UHMW ethylene‐propylene copolymer (M_w = 1167 kg mol^?1) can also be synthesized by using V4′ /Et₃Al₂Cl₃ catalytic system. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 553–561     

1‐Hexene Polymerization over Supported Titanium–Magnesium Catalyst: The Effect of Composition of the Catalytic System and Polymerization Conditions on Temperature Dependence of the Polymerization Rate

The effect of temperature on the rate of 1‐hexene polymerization over supported titanium–magnesium catalyst of composition TiCl₄/D₁/MgCl₂ + AlR₃/D₂ (D₁ is dibutyl phthalate, D₂ is propyltrimethoxysilane, and AlR₃ is an organoaluminum cocatalyst) is studied. The unusual data that the polymer rate decreases when temperature is increased from 30 to 70 °C are obtained. The 1‐hexene polymerization rate and the pattern of changes in polymerization rate with temperature depend on a combination of factors such as cocatalyst (AlEt₃ or Al(i‐Bu)₃) and presence/absence of hydrogen and an external donor in the reaction mixture. These factors differ in their effects on catalytic activity at different polymerization temperatures, so the temperature coefficient (E_eff) values calculated using the Arrhenius dependence of the polymerization rate on polymerization temperature vary greatly. The “normal” Arrhenius plot where polymerization rate increases with temperature is observed only for polymerization with the Al(i‐Bu)₃ cocatalyst in the presence of hydrogen and without an external donor. Formation of high‐molecular‐weight polyhexene at low polymerization temperatures results in catalyst particle fragmentation, which may additionally contribute to the increase in polymerization rate as polymerization temperature is reduced.     

Effect of cocatalyst on the chain microstructure of polyethylene made with CGC‐Ti/MAO/B(C6F5)3

This investigation studied the solution polymerization of ethylene in Isopar E in a semibatch reactor using CGC‐Ti as catalyst and methylalumoxane (MAO) and tris(pentaflourophenyl)borane [B(C₆F₅)₃] as cocatalysts. The effects of cocatalyst type and amount on the chain microstructure were investigated. ¹³C NMR and gel permeation chromatography were used to determine the long‐chain branching (LCB) content and molecular weight distribution (MWD), respectively, of the samples. It was observed that higher concentrations of MAO increased the LCB content and decreased the molecular weight of the polymer. On the other hand, increasing the amount of B(C₆F₅)₃ lowered the LCB content, increased the molecular weight, and broadened MWD significantly. We believe that this approach can be used as an efficient way to control the microstructure of polyolefins made with these catalytic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3055–3061, 2004     

Polymerization of ethylene using a high-activity Ziegler–Natta catalyst. II. Molecular weight regulation

This article describes studies on the variables that regulate the molecular weight in ethylene polymerization using a highly active Ziegler–Natta catalyst with hydrogen for molecular weight control. The dependence of the degree of polymerization on the concentration of catalyst, cocatalyst, monomer, partial pressure of hydrogen, and temperature has been established. The rate constant for chain transfer with cocatalyst has been evaluated. © 1993 John Wiley & Sons, Inc.     

Synthesis of branched polyethylene by ethylene homopolymerization using titanium catalysts that contain a bridged bis(phenolate) ligand

The synthesis of branched polyethylene from single ethylene feed has been achieved by using a methylaluminoxane‐activated titanium complex bearing a tetradentate bis(phenolate) ligand with a 1,4‐dithiabutanediyl bridge 1 . This catalyst produces polyethylene with activities up to 6200 kg polymer/mol h bar. As evidenced by ¹³C NMR analyses, the polyethylenes contain ethyl, n‐butyl, and long‐chain (n‐hexyl or longer) branches in a range variable from 0.2 to 2.0%, depending on the experimental parameters. NMR and gas chromatography/mass spectrometry analyses suggest that such polymer microstructure arises from the in situ production of oligomers and their subsequent incorporation into the growing polyethylene chain. The broad molecular weight distribution of these polyethylenes indicates the presence of different catalytic species. The related catalyst system 2 bearing a longer 1,5‐dithiapentanediyl bridge produces linear polyethylene with moderate activity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2815–2822, 2004     

Controlled polymerization of methyl acrylate for high‐molecular‐weight polymers by pentafluorophenylbis(triflyl)methane‐promoted group transfer polymerization using triisopropylsilyl ketene acetal

The group transfer polymerization (GTP) of methyl acrylate (MA) was studied using pentafluorophenylbis(triflyl)methane (C₆F₅CHTf₂) as the organocatalyst and 1‐trimethylsiloxy‐, 1‐triethylsiloxy‐, and 1‐triisopropylsiloxy‐1‐methoxy‐2‐methyl‐1‐propene (MTS^Me, MTS^Et, and MTS^iPr, respectively) as the initiators. The C₆F₅CHTf₂‐promoted GTP of MA using MTS^iPr proceeded in a living nature to produce poly(methyl acrylate)s (PMAs) with controlled molecular weights and narrow molecular weight distributions, which allowed the synthesis of high‐molecular‐weight PMA with the number‐average molecular weight (M_n(SEC)) of up to 108,000 and the polydispersity (M_w/M_n) of 1.07. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry measurement revealed that the obtained PMA possessed the chain end structure that originated from MTS^iPr, showing that the C₆F₅CHTf₂‐promoted GTP of MA proceeded without any side reactions. In addition, the kinetic study and the postpolymerization experiment supported the living manner of the polymerization. Moreover, the block copolymerization of MA and n‐butyl acrylate (nBA) smoothly proceeded to afford the well‐defined PMA‐block‐poly(n‐butyl acrylate) (PnBA). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Highly active ethylene polymerization and copolymerization with norbornene using bis(imino‐indolide) titanium dichloride–MAO system

A catalytic system of new titanium complexes with methylaluminoxane (MAO) was found to effectively polymerize ethylene for high molecular weight polyethylene as well as highly active copolymerization of ethylene and norbornene. The bis (imino‐indolide)titanium dichlorides (L₂TiCl₂, 1 – 5 ), were prepared by the reaction of N‐((3‐chloro‐1H‐indol‐2‐yl)methylene)benzenamines with TiCl₄, and characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. The solid‐state structures of 1 and 4 were determined by X‐ray diffraction analysis to reveal the six‐coordinated distorted octahedral geometry around the titanium atom with a pair of chlorides and ligands in cis‐forms. Upon activation by MAO, the complexes showed high activity for homopolymerization of ethylene and copolymerization of ethylene and norbornene. A positive “comonomer effect” was observed for copolymerization of ethylene and norbornene. Both experimental observations and paired interaction orbital (PIO) calculations indicated that the titanium complexes with electron‐withdrawing groups in ligands performed higher catalytic activities than those possessing electron‐donating groups. Relying on different complexes and reaction conditions, the resultant polyethylenes had the molecular weights M_w in the range of 200–2800 kg/mol. The influences on both catalytic activity and polyethylene molecular weights have been carefully checked with the nature of complexes and reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3415–3430, 2007     

Influence of the particle size of the MgCl2 support on the performance of Ziegler catalysts in the polymerization of ethylene to ultra‐high molecular weight polyethylene and the resulting polymer properties

A highly systematic size series of Ziegler catalysts with similar porosities and surface textures are synthesized by varying the stirring speed during the MgCl₂ support synthesis. Besides the mean particle size, the only substantial difference observed between the various catalysts is the size and number of nodules per particle. Varying the mean diameter of the catalyst particles between 1.5 and 11.9 µm, leads to a pronounced impact on the activity in ultra‐high molecular weight polyethylene (UHMWPE) polymerization, while the M_w capabilities are only affected to a limited extend. In addition, it is observed that both the M_ws as the polymer bulk density (BD) increases during the course of the polymerization. This particularity allows to optimize the M_w and/or BD at a set polymer size, by tuning the catalyst particle size. This is particularly interesting in UHMWPE production, as control of the morphological and structural properties of the UHMWPE reactor powders are critical for efficient processing as well as the performance of the final product. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2679–2690     

Synthesis of tetracycline‐imprinted polymer microspheres by reversible addition–fragmentation chain‐transfer precipitation polymerization using polyethylene glycol as a coporogen

Tetracycline (TC)‐imprinted microspheres have been synthesized by reversible addition–fragmentation chain‐transfer precipitation polymerization using PEG as a coporogen. In the synthesis, methacrylic acid and ethylene dimethacrylate were used as the functional monomer and cross‐linker, respectively. 2,2′‐Azobisisobutyronitrile was the initiator, and cumyl dithiobenzoate was the chain‐transfer reagent. Although monodispersed microspheres were obtained using acetonitrile as porogen, the particles cannot be used in the column extraction because of the high backpressure. To increase the porosity of the material, PEG was introduced as a coporogen. The influence of the molecular weight and concentration of PEG on the morphology, binding affinity, and porosity of the molecularly imprinted polymers (MIPs) have been studied. The results demonstrated that PEG as a macroporogen increased the porosity of the polymers. Meanwhile, the column backpressure was reduced using the MIPs with higher porosity. The binding affinity of the MIPs was increased when a low concentration of PEG was employed, while it was decreased when the ratio of PEG 12 000/monomers was >0.8%. Under the optimized conditions, TC‐imprinted microspheres with good selectivity and size uniformity have been obtained, which facilitates its application in the column extraction for TC determinations.     

Ultrahigh molecular weight polyethylene produced by a bis(phenoxy‐imine) titanium complex supported on latex particles

The applicability of latex particle supports for non‐Cp type metallocene catalysts for ethylene polymerization is presented. Polystyrene latex particles were prepared by miniemulsion polymerization and functionalized with poly(ethyleneoxide)chains and pyridyl groups on the surface. These latex particles were chosen to demonstrate that a support with nucleophilic substituents on the surface can act as a carrier for a (phenoxy‐imine) titanium complex (titanium FI‐catalyst) to produce ultrahigh molecular weight polyethylene (UHMWPE). The composition of the support, the concentration of pyridyl groups on the surface, and the crosslinking of the support were optimized to provide a system where the FI‐catalyst resulted in the formation of polyethylene with a M_w of more than 6,000,000 and a relatively narrow molecular weight distribution of 3.0 ± 0.5. High activities for long polymerization times greater than 6 h resulted in a catalyst system exhibiting productivities of up to 15,000 g PE/g cat. or 7,000,000 g PE/g Ti. The resulting polymer properties showed that nucleophilic groups on the latex particle support did not negatively impact the catalyst by blocking the active site but instead created a stable environment for the titanium catalyst. In particular, pyridyl groups on the surface of the latex particle stabilized the catalyst system probably by trapping trimethylaluminium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3103–3113, 2006     

Preparation of polyethylene/lignin nanocomposites from hollow spherical lignin‐supported vanadium‐based Ziegler–Natta catalyst

In the present article, a novel hollow spherical lignin‐supported vanadium‐based Ziegler–Natta catalyst was synthesized. The active centers of the obtained catalyst well dispersed in the lignin through the SEM‐EDX analysis. The resultant catalyst was investigated in ethylene polymerization and found to exhibit remarkable catalytic activity upon activation with ethylaluminium sesquichloride cocatalyst and ethyl trichloroacetate activator. During the polymerization, the lignin was gradually exfoliated by the polymerization force arising from the propagation of ethylene chain. The resultant PE/lignin nanocomposites preformed higher thermal stability compared to virgin PE. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of poly(3‐hexylthiophene)‐block‐poly(ethylene)‐block‐poly(3‐hexylthiophene) via a combination of ring‐opening olefin metathesis polymerization and grignard metathesis polymerization

Novel rod–coil–rod ABA triblock copolymers, poly(3‐hexylthiophene)‐block‐poly(ethylene)‐block‐poly(3‐hexylthiophene) (P3HT‐b‐PE‐b‐P3HT) were synthesized by using a combination of a Ru‐catalyzed ring‐opening metathesis polymerization of 1,4‐cyclooctadiene in the presence of a suitable chain transfer agent (CTA) and a Ni‐catalyzed Grignard metathesis polymerization of 5‐chloromagnesio‐2‐bromo‐3‐hexylthiophene followed by hydrogenation. Using this methodology, the molecular weights of the poly(butadiene) (PBD) or the P3HT blocks were controlled by adjusting the initial monomer/CTA or the initial monomer/macroinitiator ratio, respectively. In addition, the triblock structure was confirmed by selective oxidative degradation of the PBD block found in the intermediate P3HT‐b‐PBD‐b‐P3HT copolymer produced in the aforementioned method, followed by analysis of the degradation products. Thermal analysis and atomic force microscopy of P3HT‐b‐PE‐b‐P3HT revealed that the material underwent phase separation in the solid state, a feature which may prove useful for improving charge mobilities within electronic devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3810–3817     

Synthesis of ultrahigh molecular weight poly(N‐vinylcarbazole) with a high yield using low‐temperature heterogeneous‐solution polymerization

To prepare ultrahigh molecular weight (UHMW) poly(N‐vinylcarbazole) (PVCZ) with a high conversion, I heterogeneous‐solution‐polymerized N‐vinylcarbazole (VCZ) in methanol/tertiary butyl alcohol (TBA) at 25, 35, and 45 °C with a low‐temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and I investigated the effects of the polymerization conditions on the polymerization behavior and molecular parameters of PVCZ. A low‐polymerization temperature with ADMVN, a heterogeneous system with methanol, and a low chain transfer with TBA proved to be successful in obtaining PVCZ of UHMW [weight‐average molecular weight (M_w) > 3,000,000] and high conversion (>80%) with a smaller temperature rise during polymerization but still of free‐radical polymerization by an azoinitiator. The polymerization rate of VCZ in methanol/TBA at 25 °C was proportional to the 0.97 power of the ADMVN concentration, indicating a heterogeneous nature for the polymerization. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol/TBA at 25 °C with an ADMVN concentration of 0.0001 mol/mol of VCZ, an M_w of 3,230,000 was obtained, with a polydispersity index of 2.4. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 539–545, 2001     

Hydrogenation of polystyrene‐b‐polybutadiene‐b‐polystyrene mediated by group (IV) metal metallocene complexes

Various group (IV) metal complexes, namely bis(cyclopentadienyl) titanium dichloride, bis(pentamethylcyclopentadienyl) titanium dichloride, cyclopentadienyl titanium trichloride, pentamethylcyclopentadienyl titanium trichloride, bis(cyclopentadienyl) zirconium dichloride, and bis(cyclopentadienyl) hafnium dichloride, were used as the catalysts for mediating styrene–butadiene–styrene hydrogenation. The catalytic efficiency of these catalysts was examined. The results show that catalyst activity strongly depends on the chemical structure of the metallocene complex. We also found that trialkylaluminum has a significant influence on the hydrogenation activity and thermal stability of metallocene catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2141–2149     

Exceptionally high molecular weight linear polyethylene by using N,N,N′‐Co catalysts appended with a N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group

The bis(arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC₆H₄)₂CH}₂–4‐NO₂}]‐6‐(CMeNAr)C₅H₃N (Ar = 2,6‐Me₂C₆H₃ L1 , 2,6‐Et₂C₆H₃ L2 , 2,6‐i‐Pr₂C₆H₃ L3 , 2,4,6‐Me₃C₆H₂ L4 , 2,6‐Et₂–4‐MeC₆H₂ L5 ), each containing one N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group, have been synthesized by two successive condensation reactions from 2,6‐diacetylpyridine. Their subsequent treatment with anhydrous cobalt (II) chloride gave the corresponding N,N,N′‐CoCl₂ chelates, Co1 – Co5 , in excellent yield. All five complexes have been characterized by ¹H/¹⁹F NMR and IR spectroscopy as well as by elemental analysis. In addition, the molecular structures of Co1 and Co3 have been determined and help to emphasize the differences in steric properties imposed by the inequivalent N‐aryl groups; distorted square pyramidal geometries are adopted by each complex. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), precatalyts Co1 – Co5 collectively exhibited very high activities for ethylene polymerization with 2,6‐dimethyl‐substituted Co1 the most active (up to 1.1 × 10⁷ g (PE) mol^?1 (Co) h^?1); the MAO systems were generally more productive. Linear polyethylenes of exceptionally high molecular weight (M_w up to 1.3 × 10⁶ g mol^?1) were obtained in all cases with the range in dispersities exhibited using MAO as co‐catalyst noticeably narrower than with MMAO [M_w/M_n: 3.55–4.77 ( Co1 – Co5 /MAO) vs. 2.85–12.85 ( Co1 – Co5 /MMAO)]. Significantly, the molecular weights of the polymers generated using this class of cobalt catalyst are higher than any literature values reported to date using related N,N,N‐bis (arylimino)pyridine‐cobalt catalysts.     

Vanadium(III) complexes containing phenoxy–imine–thiophene ligands: Synthesis,characterization and application to homo‐ and copolymerization of ethylene

A set of vanadium(III) complexes, namely {SNO}VCl₂(THF)₂ ( 2a , SNO = thiophene‐(N═CH)‐phenol; 2b , SNO = 5‐phenylthiophene‐(N═CH)‐phenol; 2c , SNO = 5‐phenylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2d , SNO = 5‐methylthiophene‐(N═CH)‐phenol; 2e , SNO = 5‐methylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2f , SNO = 5‐methylthiophene‐(N═CH)‐2‐methylphenol; 2g , SNO = 5‐methylthiophene‐(N═CH)‐4‐fluorophenol), were synthesized by reaction of VCl₃(THF)₃ with phenoxy–imine–thiophene proligands ( 1a – g ). All vanadium(III) complexes were characterized using elemental analysis and infrared and electron paramagnetic resonance spectroscopies. Upon activation with methylaluminoxane (MAO), vanadium precatalysts 2a – g proved active in the polymerization of ethylene (213.6–887.2 kg polyethylene (mol[V])⁻¹⋅h⁻¹), yielding high‐density polyethylenes with melting temperatures in the range 133–136 °C and crystallinities varying from 28 to 41%. The 2e/ MAO catalyst system was able to copolymerize ethylene with 1‐hexene affording poly(ethylene‐co ‐1‐hexene)s with melting temperatures varying from 126 to 102 °C and co‐monomer incorporation in the range 3.60–4.00%.     

An experimental and computational evaluation of ethylene/styrene copolymerization with a homogeneous single‐site titanium(IV)‐constrained geometry catalyst

Styrene was copolymerized with ethylene using the geometry constrained Me₂Si(Me₄Cp)(N‐tert‐butyl)TiCl₂ Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005