Living Polymerization Of Ethylene Research Articles

Synthesis of polyolefin elastomers from amine-imine nickel-catalyzed ethylene polymerization

The catalytic synthesis of polyolefin elastomers by using ethylene as a sole feedstock is fascinating, while currently reported chain walking catalysts are only limited to α-diimine type. In this contribution, we developed alternative amine-imine nickel catalysts for ethylene polymerization to prepare polyolefin elastomers. The cooperative effect of steric hindrance between the less bulky amine moiety and the bulky imine moiety significantly enhanced the performance of amine-imine nickel-catalyzed ethylene polymerization. The amine-imine nickel catalysts also showed excellent controlled behavior for ethylene polymerization, and living ethylene polymerization was also realized to generate narrowly distributed polyethylenes. The microstructure of the resultant polyethylenes could be tuned by catalyst structure, reaction temperature, and ethylene pressure. The polyethylenes produced by Ni2 with the cyclic amine have higher long-chain branching contents, therefore showing better elastic properties. The strain-at-break value of 888.0 % and the strain recovery value of > 79.0 % are super to most values of polyolefin elastomers generated from α-diimine nickel catalysts.

Amphiphilic Polyethylene-b-poly(L-lysine) Block Copolymer: Synthesis, Self-Assembly, and Responsivity

Polyethylene-b-polypeptide copolymers are biologically interesting, but studies of their synthesis and properties are very few. This paper reports synthesis and characterization of well-defined amphiphilic polyethylene-block-poly(L-lysine) (PE-b-PLL) block copolymers by combining nickel-catalyzed living ethylene polymerization with controlled ring-opening polymerization (ROP) of ε-benzyloxycarbonyl-L-lysine-N-carboxyanhydride (Z-Lys-NCA) and sequential post-functionalization. Amphiphilic PE-b-PLL block copolymers self-assembled into spherical micelles with a hydrophobic PE core in aqueous solution. The pH and ionic responsivities of PE-b-PLL polymeric micelles were investigated by means of fluorescence spectroscopy, dynamic light scattering, UV-circular dichroism, and transmission electron microscopy. The variation of pH values led to the conformational alteration of PLL from α-helix to coil, thereby changing the micelle dimensions.

Distorted Sandwich α‐Diimine PdII Catalyst: Linear Polyethylene and Synthesis of Ethylene/Acrylate Elastomers

AbstractThe introduction of m‐xylyl substituents to α‐diimine PdII catalyst promotes living ethylene polymerization at room temperature and low pressure to yield high molecular weight polyethylene (PE) with low branching (<17/1000 C). m‐Xylyl groups provide a highly effective blockage to the axial sites of the catalytic center and form a distorted sandwich geometry. The shielding prevents chain‐transfer and easy accessibility of polar monomers, leading to a living polymerization. Conducting a light irradiation as part of the one‐step metal‐organic insertion light initiated radical (MILRad) process leads to diblock copolymers of ethylene and acrylates. Incorporation of different acrylate block sequences can significantly modify the mechanical and chemical properties of block copolymers which can be modulated to be a hard plastic, elastomer, or semi‐amorphous polymer.

Distorted Sandwich α-Diimine PdII Catalyst: Linear Polyethylene and Synthesis of Ethylene/Acrylate Elastomers.

The introduction of m-xylyl substituents to α-diimine PdII catalyst promotes living ethylene polymerization at room temperature and low pressure to yield high molecular weight polyethylene (PE) with low branching (<17/1000 C). m-Xylyl groups provide a highly effective blockage to the axial sites of the catalytic center and form a distorted sandwich geometry. The shielding prevents chain-transfer and easy accessibility of polar monomers, leading to a living polymerization. Conducting a light irradiation as part of the one-step metal-organic insertion light initiated radical (MILRad) process leads to diblock copolymers of ethylene and acrylates. Incorporation of different acrylate block sequences can significantly modify the mechanical and chemical properties of block copolymers which can be modulated to be a hard plastic, elastomer, or semi-amorphous polymer.

Polar Additive Triggered Branching Switch and Block Polyolefin Topology in Living Ethylene Polymerization

Branching is paramount in polyolefins and their copolymers because it renders state-of-the-art topologies and thus directly determines polymer properties. A polar additive, commonly acting as a coo...

Living regioselective copolymerization of ethylene with nonconjugated bicyclic dienes using (salicylaldiminato)(β-enaminoketonato) titanium catalysts

A series of heteroligated (salicylaldiminato)(beta-enaminoketonato) titanium complexes [3-(t)Bu-2-OC(6)H(3)CH N(C(6)F(5))] [PhN=C(CF(3))CHCRO]TiCl(2) [3a: R Ph, 3b: R C(6)H(4)Cl(p), 3c: R = C(6)H(4)OMe(p), 3d: R = C(6)H(4)Me(p), 3e: R = C(6)H(4)Me(o)] were synthesized and characterized. Molecular structures of 3b and 3c were further confirmed by X-ray crystallographic analyses. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts displayed favorable ability to incorporate 5-vinyl-2-norbornene (VNB) and 5-ethylidene-2-norbornene (ENB) into the polymer chains, affording high-molecular weight copolymers with high-comonomer incorporations and alternating sequence under the mild conditions. The comonomer concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resultant copolymer. At initial comonomer concentration of higher than 0.4 mol/L, the titanium complexes with electron-donating groups in the beta-enaminoketonato moiety mediated room-temperature living ethylene/VNB or ENB copolymerizations. Polymerization results coupled with density functional theory calculations suggested that the highly controlled living copolymerization is probably a consequence of the difficulty in chain transfer of VNB (or ENB)-last-inserted species and some characteristics of living ethylene polymerization under limited conditions. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4626-4638, 2011

Ethylene and Ethylene/α-Olefin (Co)Polymerization Behavior of Bis(phenoxy−imine)Ti Catalysts: Significant Substituent Effects on Activity and Comonomer Incorporation

The ethylene and ethylene/α-olefin (co)polymerization behavior of bis(phenoxy−imine)Ti complexes 1−7 possessing a series of substituents ortho to the phenoxy O's (ortho substituents 1, iPr; 2, cyclohexyl; 3, cyclooctyl; 4, cyclododecyl; 5, tBu; 6, CMe2Ph; 7, Ph) with dried methylaluminoxane activation was investigated. At 50 °C, all complexes displayed some of the characteristics of living ethylene polymerization and produced polyethylenes (PEs) with very narrow molecular weight distributions (Mw/Mn 1.08−1.19, Mw 14 900−62 100), albeit under limited conditions. Generally, the Ti complexes with sterically bulkier ortho substituents exhibited higher activities [e.g., 6: activity 93.2 kg of PE/(mol of cat. min)]; the ortho substituents with quaternary α-C atoms attached to the phenoxy rings, providing higher activities than those with tertiary α-C atoms on the basis of the steric bulk of the entire ortho substituent. To our surprise, complex 7 incorporating an ortho phenyl group displayed the highest activit...

Noncovalent Interactions in o-Fluorinated Post-titanocene Living Ethylene Polymerization Catalyst

Multinuclear NMR spectroscopic studies of polymerization-active species generated by activation of o-F-substituted and nonsubstituted bis(enolatoimine) titanium complexes with MAO evidence a noncovalent interaction of the o-F moieties with the metal center, which is likely to facilitate living ethylene polymerization via suppression of chain transfer and of β-hydrogen transfer processes.

Longstanding living polymerization of ethylene: substituent effect on bridging carbon of 2-pyridinemethanamine nickel catalysts

Bulky 2-pyridinemethanamine nickel complex activated by MAO was used as a catalyst to conduct longstanding living ethylene polymerization under atmospheric pressure to produce branched polyethylene.

Bis(pyrrolide‐imine) Ti Complexes with MAO: A New Family of High Performance Catalysts for Olefin Polymerization

AbstractFor Abstract see ChemInform Abstract in Full Text.

Living copolymerization of ethylene with norbornene catalyzed by bis(pyrrolide-imine) titanium complexes with MAO.

Bis(pyrrolide-imine) Ti complexes in conjunction with methylalumoxane (MAO) were found to work as efficient catalysts for the copolymerization of ethylene and norbornene to afford unique copolymers via an addition-type polymerization mechanism. The catalysts exhibited very high norbornene incorporation, superior to that obtained with Me(2)Si(Me(4)Cp)(N-tert-Bu)TiCl(2) (CGC). The sterically open and highly electrophilic nature of the catalysts is probably responsible for the excellent norbornene incorporation. The catalysts displayed a marked tendency to produce alternating copolymers, which have stereoirregular structures despite the C(2) symmetric nature of the catalysts. The norbornene/ethylene molar ratio in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. At norbornene/ethylene ratios larger than ca. 1, the catalysts mediated room-temperature living copolymerization of ethylene and norbornene to form high molecular weight monodisperse copolymers (M(n) > 500,000, M(w)/M(n) < 1.20). (13)C NMR spectroscopic analysis of a copolymer, produced under conditions that gave low molecular weight, demonstrated that the copolymerization is initiated by norbornene insertion and that the catalyst mostly exists as a norbornene-last-inserted species under living conditions. Polymerization behavior coupled with DFT calculations suggested that the highly controlled living polymerization stems from the fact that the catalysts possess high affinity and high incorporation ability for norbornene as well as the characteristics of a living ethylene polymerization though under limited conditions (M(n) 225,000, M(w)/M(n) 1.15, 10-s polymerization, 25 degrees C). With the catalyst, unique block copolymers [i.e., poly(ethylene-co-norbornene)(1)-b-poly(ethylene-co-norbornene)(2), PE-b-poly(ethylene-co-norbornene)] were successfully synthesized from ethylene and norbornene. Transmission electron microscopy (TEM) indicated that the PE-b-poly(ethylene-co-norbornene) possesses high potential as a new material consisting of crystalline and amorphous segments which are chemically linked.

Unprecedented living olefin polymerization derived from an attractive interaction between a ligand and a growing polymer chain.

Ti complexes incorporating fluorine-containing phenoxy-imine chelate ligands (fluorinated Ti-FI catalysts) have been demonstrated to induce an unprecedented living polymerization effect with both ethylene and propylene, through an attractive interaction between the fluorine atom in the ligand and a beta-hydrogen atom on the growing polymer chain. With the aid of this attractive interaction, highly controlled living ethylene polymerization, highly-syndiospecific living propylene polymerization, the synthesis of unique block copolymers from ethylene and propylene, and the catalytic production of monodisperse polyethylene and Zn-terminated polyethylene have been realized. The attractive interaction provides a conceptually new strategy for the achievement of controlled living olefin polymerization.

Titanium Catalysts with Ancillary Phenoxyketimine Ligands for Living Ethylene Polymerization

New titanium catalysts with ancillary, non-fluorinated phenoxyketimine ligands have been synthesized and found to be active for living ethylene polymerization.

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

AbstractFor Abstract see ChemInform Abstract in Full Text.

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

This paper reviews a new family of olefin polymerization catalysts. The catalysts, named FI catalysts, are based on non-symmetrical phenoxyimine chelate ligands combined with group 4 transition metals and were developed using “ligand-oriented catalyst design”. FI catalysts display very high ethylene polymerization activities under mild conditions. The highest activity exhibited by a zirconium FI catalyst reached an astonishing catalyst turnover frequency (TOF) of 64,900 s –1 atm –1, which is two orders of magnitude greater than that seen with Cp2ZrCl2 under the same conditions. In addition, titanium FI catalysts with fluorinated ligands promote exceptionally high-speed, living ethylene polymerization and can produce monodisperse high molecular weight polyethylenes (Mw/Mn<1.2, max. Mn>400,000) at 50 °C. The maximum TOF, 24,500 min –1 atm –1, is three orders of magnitude greater than those for known living ethylene polymerization catalysts. Moreover, the fluorinated FI catalysts promote stereospecific room-temperature living polymerization of propylene to provide highly syndiotactic monodisperse polypropylene (max. [rr] 98%). The versatility of the FI catalysts allows for the creation of new polymers which are difficult or impossible to prepare using group 4 metallocene catalysts. For example, it is possible to prepare low molecular weight (Mv∼103) polyethylene or poly(ethylene-co-propylene) with olefinic end groups, ultra-high molecular weight polyethylene or poly(ethylene-co-propylene), high molecular weight poly(1-hexene) with atactic structures including frequent regioerrors, monodisperse poly(ethylene-co-propylene) with various propylene contents, and a number of polyolefin block copolymers [e.g., polyethylene-b-poly(ethylene-co-propylene), syndiotactic polypropylene-b-poly(ethylene-co-propylene), polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene]. These unique polymers are anticipated to possess novel material properties and uses.

New Titanium Complexes Bearing Two Indolide−Imine Chelate Ligands for the Polymerization of Ethylene

New titanium complexes 5−8 with two indolide−imine chelate ligands [7-(RNCH)C8H5N]2TiCl2 (R: 5, phenyl; 6, 2,6-difluorophenyl; 7, 2,4,6-trifluorophenyl; 8, pentafluorophenyl) were synthesized and investigated as ethylene polymerization catalysts. On activation with methylalumoxane (MAO), all of the complexes were active ethylene polymerization catalysts at 25 °C to produce linear polyethylenes. The catalytic activity (TOF) increased sharply with the number of fluorine atom in the ligand. In addition, complexes 5−8 potentially exhibit the characteristics of a living ethylene polymerization. Complexes 6 and 7 promoted room temperature living ethylene polymerization to produce polyethylenes having extremely narrow molecular weight distributions (6, Mw/Mn 1.09−1.14; 7, Mw/Mn 1.05−1.23). On the other hand, at −10 °C complex 8 afforded monodisperse polyethylenes (Mw/Mn 1.12−1.25), with exceptionally high activities for a living ethylene polymerization (TOF: maximum 1155 min-1 atm-1). Using complex 7/MAO catal...

Living polymerization of ethylene catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands.

Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl(2)[eta(2)-1-[C(H)=NR]-2-O-3-(t)Bu-C(6)H(3)](2) [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R = 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6), R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl(4) in good yields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structure in which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and the two chlorine atoms are located cis to one another, the same spatial disposition as that for the corresponding nonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 are very similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O, N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogen are different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms. Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to produce high molecular weight polyethylenes (M(n) > 400 000) with extremely narrow polydispersities (M(w)/M(n) < 1.20). Very high activities (TOF > 20 000 min(-1) atm(-1)) were observed that are comparable to those of Cp(2)ZrCl(2)/MAO at high polymerization temperatures (25, 50 degrees C). Complexes 2-4, which have a fluorine atom adjacent to the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 degrees C, whereas complexes 5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having M(w)/M(n) values of ca. 2 with beta-hydrogen transfer as the main termination pathway. These results together with DFT calculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirement for the high-temperature living polymerization, and the fluorine of the active species for ethylene polymerization interacts with a beta-hydrogen of a polymer chain, resulting in the prevention of beta-hydrogen transfer. This catalyst system was used for the synthesis of a number of unique block copolymers such as polyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.

New Titanium Complexes Having Two Indolide-Imine Chelate Ligands for Living Ethylene Polymerization

Abstract Three new titanium complexes having two indolide-imine ligands were synthesized and investigated as ethylene polymerization catalysts. These complexes using MAO as a cocatalyst promoted ethylene polymerization at 25 °C to produce polyethylenes (Mn:11000–41800) having narrow molecular weight distributions (Mw/Mn: 1.11–1.14), displaying very high activities (52–288 kg-PE/mol-Ti·h·atm).