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     

Course of the terpolymerization of ethylene,propylene, and dicyclopentadiene. I. Single initial addition of dicyclopentadiene

Detailed studies were made of the course of the terpolymerization of ethylene, propylene, and dicyclopentadiene to form unsaturated elastomers. All the dicyclopentadiene was added at the start of a polymerization, but the monoolefins were added continuously throughout the run. Under these conditions, unsaturation of the initial polymer is fairly high but decreases steadily as the reaction progresses. From analyses of the initial samples from each run, the catalyst of VCl₄ (with Al₂Et₃Cl₃ cocatalyst), with heptane as the polymerization solvent, was most efficient for introducing unsaturation into terpolymer. This system also produces gel in the terpolymer in the latter stages of reaction, however. Catalysts of VCl₄, VOCl₃, or V(C₅H₇O₂)₃, with Al₂Et₃Cl₃ cocatalyst, in benzene solvent gave terpolymers of quite similar unsaturations. With all systems, terpolymer yield increases very rapidly in the first few minutes of reaction, then very slowly for the remainder of the 30-min. reaction time, reflecting the rapid loss of activity of the vanadium catalysts. Molecular weight growth of the terpolymer prepared in heptane was extremely rapid, reaching a high value in a few minutes. When prepared in benzene, the terpolymers showed a steady increase in molecular weight throughout the reaction but reached only a moderate final value (as expressed by inherent viscosity).     

Homo‐ and Copolymerization of Butadiene Catalyzed by an Bis(imino)pyridyl Vanadium Complex

Summary: The bis(imino)pyridyl vanadium(III ) complex [VCl₃{2,6‐bis[(2,6‐iPr₂C₆H₃)NC(Me)]₂(C₅H₃N)}] activated with different aluminium cocatalysts (AlEt₂Cl, Al₂Et₃Cl₃, MAO) promotes chemoselective 1,4‐polymerization of butadiene with activity values higher than classical vanadium‐chloride‐based catalysts. The polymer structure depends on the nature of the cocatalyst employed. The MAO‐activated complex was also found to be active in ethylene‐butadiene copolymerization, producing copolymers with up to 45 mol‐% of trans‐1,4‐butadiene. Crystalline polyethylene and trans‐1,4‐poly(butadiene) segments were detected in these copolymers by DSC and ¹³C NMR spectroscopy.

     

POLYMERIZATION OF ETHYLENE AND PROPYLENE WITH VCL4-BUTYLLITHIUM CATALYSTS

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.     

Strukturen zweifach metallierter Derivate von 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentan mit Lithium und Aluminium sowie zweier Donor‐substituierter Digallane

Structural Characterization of Bis(metallated) Derivatives of 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentane with Lithium and Aluminum and of two Donor‐substituted Digallanes The diaminopropane derivative Me₂C[CH₂N(H)SiMe₃]₂ is metallated with n‐butyllithium and lithium tetrahydridoaluminate to obtain Me₂C[CH₂N(Li)SiMe₃]₂ and Me₂C[CH₂N(Li)SiMe₃][CH₂N(AlH₂)SiMe₃], respectively. Both compounds exhibit a central eight‐membered ring, Li₄N₄ or Li₂Al₂N₄. Me₂C[CH₂N(Li)SiMe₃]₂ reacts with Ga₂Cl₄ · 2dioxane under formation of the corresponding tetra(amino)digallane. This is monomeric, in contrast to a dimeric tetraalkoxy‐substituted digallane, Ga₄O^tBu₈. All compounds were characterized by single crystal X‐ray crystallography.     

Vanadium- or vanadylacetylacetonate as a cocatalyst for the terpolymerization of ethylene,propylene, and dicyclopentadiene

Vanadium trisacetylacetonate [V(C₅H₇O₂)₃] and vanadyl bisacetylacetonate [VO-(C₅H₇O₂)₂] were found to be satisfactory catalysts (with Al₂Et₃Cl₃ cocatalyst) for the terpolymerization of ethylene, propylene, and dicyclopentadiene to unsaturated, sulfurcurable elastomers. Polymerization solvents of heptane or benzene were used. Best yields of terpolymers were obtained in benzene. Terpolymers with unsaturations of greater than ?0.20 mole C?C/kg. can be cured with a sulfur-based vulcanzing recipe. Both acetylacetonates produced terpolymers, in benzene, with practically equivalent properties. They also appeared to be nearly equal to corresponding terpolymers made with catalysts of VOCl₃ or VCl₄.     

Electron spin resonance studies of ziegler-natta-type catalysts. The complex derived from dichlorobis (η-cyclopentadienyl) vanadium (Cp2VCl2) with ethylaluminium sesquichloride to polymerize ethylene

The reaction between Cp₂VCl₂ (Cp = η-cyclopentadienyl) in CH₂Cl₂ and Et₃Al₂Cl₃ or Et₂AlCl in η-heptane yields three paramagentic species giving the ESR parameters a_γ = 4.11 mT, g = 1.991 (I); a_γ = 7.46 mT, g = 1.982 (II); a_γ = 7.398 mT, g = 1.985 (III). Ethylene was polymerized using these catalysts; the solution was examined by the electron spin resonance technique before the polymerization and during the course of the reaction. The catalyst activity decayed quickly, and the mechanism of the reaction is discussed.     

Olefin polymerization with Me4Cp–Amido complexes with electron‐withdrawing groups

A series of Me₄Cp–amido complexes {[η⁵:η¹‐(Me₄C₅)SiMe₂NR]TiCl₂; R = t‐Bu, 1 ; C₆H₅, 2 ; C₆F₅, 3 ; SO₂Ph, 4 ; or SO₂Me, 5 } were prepared and investigated for olefin polymerization in the presence of methylaluminoxane (MAO). X‐ray crystallography of complexes 3 and 4 revealed very long Ti N bonds relative to the bonds of 1 . These complexes were employed for ethylene–styrene copolymerizations, styrene homopolymerizations, and propylene homopolymerizations in the presence of MAO. The productivities of the catalysts derived from 3 – 5 were much lower than the productivity of the catalyst derived from 1 for the propylene polymerizations and ethylene–styrene copolymerizations, whereas the styrene polymerization activities were much higher for the catalysts derived from 3 – 5 than for the catalyst derived from 1 . The polymerization behavior of the catalysts derived from the metallocenes 3 – 5 were more reminiscent of monocyclopentadienyl titanocene Cp′TiX₃/MAO catalysts than of CpATiX₂/MAO catalysts such as 1 containing alkylamido ligands. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4649–4660, 2000     

Synthesis,structural characterization,and ethylene polymerization behavior of (arylimido)vanadium(V) complexes bearing tridentate Schiff base ligands

A series of novel (arylimido)vanadium(V) complexes bearing tridentate salicylaldiminato chelating ligands, V(N‐2,6‐Me₂C₆H₃)Cl₂[(O‐2‐^tBu‐4‐R‐C₆H₃)CH?ND] (R = H, D = 2‐CH₃O? C₆H₄ ( 2a ); 2‐CH₃S? C₆H₄ ( 2b ); 2‐Ph₂P? C₆H₄ ( 2c ); 8‐C₉H₆N (quinoline) ( 2d ); CH₂C₅H₄N ( 2e ); R = ^tBu, D = 2‐Ph₂P? C₆H₄ ( 2f )), were prepared from V(NAr)Cl₃ by reacting with 1.0 equiv of the ligands in the presence of triethylamine in tetrahydrofuran. These complexes were characterized by ¹H, ¹³C, ³¹P, and ⁵¹V NMR spectra and elemental analysis. The structures of 2c and 2f were further confirmed by X‐ray crystallographic analysis. These (arylimido)vanadium(V) complexes are effective catalyst precursors for ethylene polymerization in the presence of Et₂AlCl as a cocatalyst and ethyl trichloroacetate as a reactivating agent. Complex 2c with a ? PPh₂ group in the sidearm was found to exhibit an exceptional activity up to 133800 kg polyethylene/mol_V h for ethylene polymerization at 75 °C, which is one of the highest activities displayed by homogeneous vanadium(V) catalysts at high temperature. Moreover, high molecular weight polymers with unimodal molecular weight distribution can be obtained, indicating the single site behavior of these catalysts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2633‐2642     

Course of the terpolymerization of ethylene,propylene, and dicyclopentadiene. II. Two-step addition of dicyclopentadiene

Terpolymerizations of ethylene, propylene, and dicyclopentadiene were carried out in which the dicyclopentadiene was added to the reaction system in two equal portions at the beginning and midpoint of each run, while the monoolefins were added continuously. In the resultant elastomers, unsaturation remains much more constant throughout the course of the polymerization than for terpolymers obtained when all dicyclopentadiene is added at the start of the reaction. Yield and molecular weight of the terpolymers produced by either technique are quite comparable, however. With VCl₄ catalyst (with Al₂Et₃Cl₃ cocatalyst) in heptane solvent, the two-step addition of the diene gave terpolymers with little gel, in contrast to the high gel in terpolymers formed with the single initial addition of the diene. This system also produced terpolymer with the highest final unsaturation and molecular weight. Catalysts of VCl₄, VOCl₃, or V(C₅H₇O₂)₃ in benzene gave terpolymers of moderate unsaturations and molecular weights.     

Stereospecific polymerization of isobutyl vinyl ether. III. Polymerization with VCl3 • LiCl

The polymerization of isobutyl vinyl ether by vanadium trichloride in n-heptane was studied. VCl₃ ? LiCl was prepared by the reduction of VCl₄ with stoichiometric amounts of BuLi. This type of catalyst induces stereospecific polymerization of isobutyl vinyl ether without the action of trialkyl aluminum to an isotactic polymer when a rise in temperature during the polymerization was depressed by cooling. It is suggested that the cause of the stereospecific polymerization might be due to the catalyst structure in which LiCl coexists with VCl₃, namely, VCl₃ ? LiCl or VCl₂ ? 2LiCl as a solid solution in the crystalline lattice, since VCl₃ prepared by thermal decomposition of VCl₄ and a commercial VCl₃ did not produce the crystalline polymer and soluble catalysts such as VCl₄ in heptane and VCl₃ ? LiCl in ether solution did not yield the stereospecific polymer. It was found that some additives, such as tetrahydrofuran or ethylene glycol diphenyl ether, to the catalyst increased the stereospecific polymerization activity of the catalysts. Influence of the polymerization conditions such as temperature, time, monomer and catalyst concentrations, and the kind of solvent on the formed polymer was also examined.     

Pentamethylcyclopentadienyl Halfsandwich Complexes of Vanadium and Tantalum with Amido‐, Imido‐ Nitrido‐ and Azido Ligands

Lithium bis(trimethylsilyl)amide, LiN(SiMe₃)₂, reacts with Cp*V(O)Cl₂ and Cp*TaCl₄ to give trimethylsilylimido complexes such as [Cp*V(NSiMe₃)(μ‐NSiMe₃)]₂ ( 7 ) and Cp*Ta(Cl)(NSiMe₃)[N(SiMe₃)₂] ( 19 ), respectively. Substitution of the chloro ligand in 19 by anionic groups leads to complexes with 3 different N‐containing ligands, Cp*Ta(X)(NSiMe₃)[N(SiMe₃)₂] (X = N₃ ( 20 ) or NPEt₃ ( 21 )). Complex 7 is air‐ and moisture‐sensitive, and several derivatives containing oxo and trimethylsiloxy ligands have been identified. Trimethylsilyl azide, Me₃Si‐N₃, is able to replace the oxygen‐containing ligands for azido ligands. The two complete series of bis(azido)‐bridged complexes, [Cp*VCl_n(N₃)_2‐n(μ‐N₃)]₂ (n = 2, 1, 0) and [Cp*TaCl_n(N₃)_3‐n(μ‐N₃)]₂(n = 3, 2, 1, 0), are accessible from the reactions of Cp*VCl₃ and Cp*TaCl₄, respectively, with trimethylsilyl azide. A bis(nitrido)‐bridged azido‐vanadium complex, [Cp*V(N₃)(μ‐N)]₂ ( 18 ), has also been obtained and structurally characterized.     

C2‐symmetry dimethylated zirconocenes activated with triisobutyl aluminum as effective homogeneous catalysts for copolymerization of olefins

We investigated the catalytic performance of both bridged unsubstituted [rac‐EtInd₂ZrMe₂, rac‐Me₂SiInd₂ZrMe₂] and 2‐substituted [rac‐Et(2‐MeInd)₂ZrMe₂), rac‐Me₂Si(2‐MeInd)₂ZrMe₂] dimethylbisindenylzirconocenes activated with triisobutyl aluminum (TIBA) as a single activator in (a) homopolymerizations of ethylene and propylene, (b) copolymerization of ethylene with propylene and hexene‐1, and (c) copolymerization of propylene with hexene‐1 (at Al_TIBA/Zr = 100‐300 mol/mol). Unsubstituted catalysts were inactive in homopolymerizations of ethylene and propylene and copolymerization of propylene with hexene‐1 but exhibited high activity in copolymerizations of ethylene with propylene and hexene‐1. 2‐Substituted zirconocenes activated with TIBA were active in homopolymerizations of ethylene and propylene and exhibited high activity in copolymerization of ethylene with propylene and hexene‐1, and in copolymerization of propylene with hexene‐1. Comparative microstructural analysis of ethylene‐propylene copolymers prepared over rac‐Me₂SiInd₂ZrMe₂ activated with TIBA or Me₂NHPhB(C₆F₅)₄ has shown that the copolymers formed upon activation with TIBA are statistical in nature with some tendency to alternation, whereas those with borate activated system show a tendency to formation of comonomer blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2934–2941, 2010     

α‐Diamine Nickel Catalysts with Nonplanar Chelate Rings for Ethylene Polymerization

A series of novel α‐diamine nickel complexes, (ArNH‐C(Me)‐(Me)C‐NHAr)NiBr₂, 1 : Ar=2,6‐diisopropylphenyl, 2 : Ar=2,6‐dimethylphenyl, 3 : Ar=phenyl), have been synthesized and characterized. X‐ray crystallographic analysis showed that the coordination geometry of the α‐diamine nickel complexes is markedly different from conventional α‐diimine nickel complexes, and that the chelate ring (N‐C‐C‐N‐Ni) of the α‐diamine nickel complex is significantly distorted. The α‐diamine nickel catalysts also display different steric effects on ethylene polymerization in comparison to the α‐diimine nickel catalyst. Increasing the steric hindrance of the α‐diamine ligand by substitution of the o‐methyl groups with o‐isopropyl groups leads to decreased polymerization activity and molecular weight; however, catalyst thermal stability is significantly enhanced. Living polymerizations of ethylene can be successfully achieved using 1 /Et₂AlCl at 35 °C or 2 /Et₂AlCl at 0 °C. The bulky α‐diamine nickel catalyst 1 with isopropyl substituents can additionally be used to control the branching topology of the obtained polyethylene at the same level of branching density by tuning the reaction temperature and ethylene pressure.     

Ethylene polymerization and ethylene/hexene copolymerization with vanadium(III) catalysts bearing heteroatom‐containing salicylaldiminato ligands

A series of novel vanadium(III) complexes bearing heteroatom‐containing group‐substituted salicylaldiminato ligands [RN?CH(ArO)]VCl₂(THF)₂ (Ar = C₆H₄, R = C₃H₂NS, 2a ; C₇H₄NS, 2c ; C₇H₅N₂, 2d ; Ar = C₆H₂tBu₂ (2,4), R = C₃H₂NS, 2b ) have been synthesized and characterized. Structure of complex 2c was further confirmed by X‐ray crystallographic analysis. The complexes were investigated as the catalysts for ethylene polymerization in the presence of Et₂AlCl. Complexes 2a–d exhibited high catalytic activities (up to 22.8 kg polyethylene/mmol_V h bar), and affording polymer with unimodal molecular weight distributions at 25–70 °C in the first 5‐min polymerization, whereas produced bimodal molecular weight distribution polymers at 70 °C when polymerization time prolonged to 30 min. The catalyst structure plays an important role in controlling the molecular weight and molecular weight distribution of the resultant polymers produced in 30 min polymerization. In addition, ethylene/hexene copolymerizations with catalysts 2a–d were also explored in the presence of Et₂AlCl, which leads to the high molecular weight and unimodal distributions copolymers with high comonomer incorporation. Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled over a wide range by the variation of catalyst structure and the reaction parameters, such as comonomer feed concentration, polymerization time, and polymerization reaction temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3573–3582, 2009     

Stereospecific polymerization of isobutyl vinyl ether by AlR3–VCln catalysts. I. Influence of preparative conditions of the catalysts

The polymerization of isobutyl vinyl ether by the VCl_n–AIR₃ system was carefully studied. The vanadium components were prepared by the reaction between VCl₄ and AlEt₃ or n-BuLi as a reducing agent. VCl₃·LiCl and VCl₂·2LiCl are the effective catalysts for the stereospecific polymerization of isobutyl vinyl ether. When VCl₃·LiCl is combined with AlR₃, a new catalytic system is formed. The effect of the preparative conditions of the various vanadium component in the AlR₃–VCl_n system shows that the effective vanadium component is trivalent. In the polymerization by VCl₃·LiCl–Al (i-Bu)₃ system, a change of the polymerization mechanism may occur at Al(i-Bu)₃/VCl₃·LiCl ratio at around 5. When the ratio is lower than 5, a cationic polymerization by VCl₃·LiCl takes place predominantly, while at ratios higher than 5, it is suggested that the polymerization proceeds by means of a VCl₃·LiClA–Al(i-Bu)₃ complex by a coordinated anionic mechanism. The polymers obtained by these catalysts are highly crystalline. Styrene was also polymerized by using the same catalysts. VCl₃·LiCl and VCl₃·LiCl–THF complex yielded amorphous polymer by cationic polymerization. When VCl₃·LiCl was combined with 6 mole-eq of Al(i-Bu)₃, the resulting polystyrene was highly crystalline and had an isotactic structure, while the VCl₂·2LiCl–Al(i-Bu)₃ (1:6) system yielded traces of polymer of extremely low stereoregularity. The results indicate that the effective vanadium component at Al/V ≧ 6 is trivalent and that the mechanism is a coordinated anionic one.     

New catalytic systems based on fluorine-containing titanium(iv) alkoxides for the synthesis of ultrahigh-molecular-weight polyethylene and olefin elastomers

The catalytic activity of the systems based on titanium(iv) alkoxides (Ti(OPrⁱ)₄, Ti(OPrⁱ)₂(OCH(CF₃)₂)₂, and Ti(OCH(CF₃)₂)₄) and mixtures of alkylaluminum chlorides (Et₂AlCl or Et₃Al₂Cl₃) with dibutylmagnesium in ethylene polymerization and ethylene copolymerization with propylene and 5-ethylidene-2-norbornene was studied. Ultrahigh-molecular-weight polyethylene with the molecular weight reaching 4.9 · 10⁶ Da was found to be formed in the homopolymerization reaction, whereas copolymerization gives ter-copolymers containing propylene (up to 35 mol.%) and 5-ethylidene-2-norbornene (4.3 mol.%) units.

     

The polymerization of ethylene with a highly active Ziegler-Natta catalyst

A soluble ethylene catalyst were obtained by mixing a methylene dichloride solution of dichlorobis(γ-cyclopentadienyl) titanium (Cp₂TiCl₂) with a heptane solution of ethylaluminium sesquichloride (Al₂Et₃Cl₃) or of diethylaluminium chloride (AlEt₂Cl). Ethylene was polymerized using these catalysts; the solution was examined by electron spin resonance technique before the polymerization and during the reaction. The catalyst activity remained constant for a long period, and the polymerization went on at the same rate for 6–8 hr. The mechanism of the reaction is discussed.     

Synthesis,characterization and ethylene polymerization by metallasilsesquioxane

Soluble complexes of group (IV) metallocenes anchored on a substituted polyhedral oligomeric silsesquioxane trisilanol support were prepared and characterized. These catalyst precursors formulated as [M(O^O^O)X] are found to be active in polymerization of ethylene at high temperature in combination with ethylaluminum sesquichloride (Et₃Al₂Cl_3, EASC) as co‐catalyst. The polyethylene obtained by these catalysts is linear, crystalline and displays narrow dispersity. The unique low molecular weight PE formed in this reaction exhibits properties comparable to commercial micronized PE waxes that have potential industrial applications in surface coating and ink formulations. Copyright © 2013 John Wiley & Sons, Ltd.     

Olefin polymerization behavior of titanium(IV) alkoxo complexes with fluorinated diolate ligands: The impact of the chelate ring size and the nature of organoaluminum compounds

Titanium(IV) coordination compounds are effectively used as precatalysts for ethylene polymerization and copolymerization with other olefins. New titanium(IV) complexes 3b – d with ligands containing two diphenylcarbinol fragments linked by the perfluorinated hydrocarbon units –CF₂– or –C₂F₄– were synthesized. The structures of complexes 3b and 3d were determined by X-ray diffraction. Titanium atoms in 3b have a distorted trigonal-bipyramidal coordination environment while spiro-complex 3d is characterized by tetrahedral molecular geometry. The catalytic behavior of complexes activated by mixtures of Bu₂Mg and alkylaluminium chlorides from among Me₂AlCl, Et₂AlCl, EtAlCl₂, and Et₃Al₂Cl₃ were studied. The resulting catalytic systems catalyze ethylene polymerization to afford ultra-high molecular weight polyethylene, suitable for modern processing methods, and the solvent-free solid state formation of super high-strength (1.37–2.75 GPa) and high-modulus (up to 138 GPa) oriented film tapes. The same catalytic systems catalyze ethylene copolymerization with 1-hexene to afford high molecular weight semicrystalline elastomeric polymers containing up to 20% of comonomer units.