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

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐^tBu‐2‐OC₆H₃CH?N(C₆F₅)] [PhN?C(CF₃)CHCRO]TiCl₂ [ 3a : R = Ph, 3b : R = C₆H₄Cl(p), 3c : R = C₆H₄OMe(p), 3d : R = C₆H₄Me(p), 3e : R = C₆H₄Me(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 β‐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. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Ethylene polymerizations,and the copolymerizations of ethylene with hexene or norbornene with highly active mono(β‐enaminoketonato) vanadium(III) catalysts

Five novel vanadium(III) complexes [PhN = C(R₂)CHC(R₁)O]VCl₂(THF)₂ ( 4a : R₁ = Ph, R₂ = CF₃; 4b : R₁ = t‐Bu, R₂ = CF₃; 4c : R₁ = CF₃, R₂ = CH₃; 4d : R₁ = Ph, R₂ = CH₃; 4e : R₁ = Ph, R₂ = H) have been synthesized and characterized. On activation with Et₂AlCl, all the complexes, in the presence of ethyl trichloroacetate (ETA) as a promoter, are highly active precatalysts for ethylene polymerization, and produce high molecular weight and linear polymers. Catalyst activities more than 16.8 kg PE/mmol_V h bar and weight‐average molecular weights higher than 173 kg/mol were observed under mild conditions. The copolymerizations of ethylene and norbornene or 1‐hexene with the precatalysts were also explored, which leads to high molecular weight copolymers with high comonomer incorporation. Catalyst activity, comonomer incorporation, and polymer molecular weight as well as polydispersity index can be controlled over a wide range by the variation of precatalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and polymerization temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2038–2048, 2008     

Novel vanadium(III) complexes with tridentate phenoxy‐phosphine [O,P(O),O] ligands: Synthesis,characterization, and catalytic behavior of ethylene polymerization and copolymerization with 10‐undecen‐1‐ol

A series of novel vanadium(III) complexes bearing tridentate phenoxy‐phosphine [O,P,O] ligands and phosphine oxide‐bridged bisphenolato [O,P?O,O] ligands, which differ in the steric and electronic properties, have been synthesized and characterized. These complexes were characterized by Fourier transform infrared spectroscopy (FTIR) and mass spectra as well as elemental analysis. Single‐crystal X‐ray diffraction revealed that complexes 3c and 4e adopt an octahedral geometry around the vanadium center. In the presence of Et₂AlCl as a cocatalyst, these complexes displayed high catalytic activities up to 22.8 kg PE/mmol_V.h.bar for ethylene polymerization, and produced high‐molecular‐weight polymers. Introducing additional oxygen atom on phosphorus atom of [O,P,O] ligands has resulted in significant changes on the aspect of steric/electronic effect, which has an impact on polymerization performance. 3c and 4c /Et₂AlCl catalytic systems were tolerant to elevated temperature (70 °C) and yielded unimodal polyethylenes, indicating the single‐site behavior of these catalysts. By pretreating with equimolar amounts of alkylaluminums, functional α‐olefin 10‐undecen‐1‐ol can be efficiently incorporated into polyethylene chains. 10‐Undecen‐1‐ol incorporation can easily reach 14.6 mol % under the mild conditions. Other reaction parameters that influenced the polymerization behavior, such as reaction temperature, Al/V (molar ratio), and comonomer concentration, are also examined in detail. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Ethylene polymerization by the chromium catalysts based on bidentate [O,PO] or [S,P] ligands

Novel chromium catalysts based on bidentate phenoxy‐phosphinoyl (HO‐2R₁‐4R₂‐6(Ph₂P?O)C₆H₂: R₁ = R₂ = H, 3a ; R₁ = tBu, R₂ = H, 3b ; R₁ = R₂ = tBu, 3c ; R₁ = R₂ = cumyl, 3d ; R₁ = anthracenyl, R₂ = H, 3e ) and thiophenol‐phosphine (HS‐2R₁‐4R₂‐6(Ph₂P)C₆H₂: R₁ = R₂ = H, 4a ; R₁ = SiMe₃, R₂ = H, 4b ) were prepared and characterized. Treatment with modified methyaluminoxane, these catalysts displayed moderate to high‐catalytic activities for ethylene polymerization. The activities of them were higher than those of the corresponding catalysts based on bidentate phenoxy‐phosphine ligands. Both the coordinated donors and the ortho‐substituent of the ligands played an important role in improving catalytic activity. The effects of reaction parameters, such as cocatalyst and Al/Cr molar ratio as well as reaction temperature, on ethylene polymerization behaviors were investigated in detail for two favorable catalytic systems, 3b /CrCl₃(thf)₃ and 4b /CrCl₃(thf)₃. Catalyst 4b /CrCl₃(thf)₃ displayed higher catalytic activity and better temperature tolerance for ethylene polymerization than 3b /CrCl₃(thf)₃. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 311–319, 2010     

Propylene Polymerization Performance of Isolated and Aggregated Ti Species Studied Using a Well‐Designed TiCl3/MgCl2 Ziegler‐Natta Model Catalyst

In propylene polymerization with MgCl₂‐supported Ziegler‐Natta catalysts, it is known that the reduction of TiCl₄ with alkylaluminum generates Ti³⁺ active species, and at the same time, leads to the growth of TiCl_x aggregates. In this study, the aggregation states of the Ti species were controlled by altering the Ti content in a TiCl₃/MgCl₂ model catalyst prepared from a TiCl₃ · 3C₅H₅N complex. It is discovered that all the Ti species become isolated mononuclear with a highly aspecific feature below 0.1 wt.‐% of the Ti content, and that the isolated aspecific Ti species are more efficiently converted into highly isospecific ones by the addition of donors than active sites in aggregated Ti species.

     

Ethylene polymerization by the new chromium catalysts based on amino‐pyrrolide ligands

A series of amino‐pyrrolide ligands ( 1–4a ) and their derivatives amino‐thiophene ligand ( 5a ), amino‐indole ligand ( 6a ) were prepared. Chromium catalysts, which were generated in situ by mixing the ligands with CrCl₃(thf)₃ in toluene, were tested for ethylene polymerization. The preliminary screening results revealed that the tridentate amino‐pyrrolide ligands containing soft pendant donor, 3a, 4a /CrCl₃(thf)₃ systems displayed high catalytic activities towards ethylene polymerization in the presence of modified methyaluminoxane. The electronic and steric factors attached to the ligand backbone significantly affected both the catalyst activity and the polymer molecular weight. Complex 4b was obtained by the reaction of CrCl₃(thf)₃ with one equivalent of the lithium salts of 4a , which was the most efficient ligand among the tested ones. The effect of polymerization parameters such as cocatalyst concentration, ethylene pressure, reaction temperature, and time on polymerization behavior were investigated in detail. The resulting polymer obtained by 4b display wax‐like and possess linear structure, low molecular weight, and unimodal distribution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 713–721, 2009     

Vanadium(V) complexes containing tetradentate amine trihydroxy ligands as catalysts for copolymerization of cyclic olefins

A series of vanadium(V) complexes bearing tetradentate amine trihydroxy ligands [NOOO], which differ in the steric and electronic properties, have been synthesized and characterized. Single crystal X‐ray analysis showed that these complexes are five or six coordinated around the vanadium center in the solid state. Their coordination geometries are octahedral or trigonal bipyramidal. In the presence of Et₂AlCl, these complexes have been investigated as the efficient catalysts for ethylene polymerization and ethylene/norbornene copolymerization at elevated reaction temperature and produced the polymers with unimodal molecular weight distributions (MWDs), indicating the single site behaviors of these catalysts. Both the steric hindrance and electronic effect of the groups on the tetradentate ligands directly influenced catalytic activity and the molecular weights of the resultant (co)polymers. Other reaction parameters that influenced the polymerization behavior, such as reaction temperature, ethylene pressure, and comonomer concentration, are also examined in detail. Furthermore, high catalytic activities of up to 3.30 kg polymer/mmol_V·h were also observed when these complexes were applied to catalyze the copolymerization of ethylene and 5‐norbornene‐2‐methanol, producing the high‐molecular‐weight copolymers (M_w = 157–400 kg/mol) with unimodal MWDs (M_w/M_n = 2.5–3.0) and high polar comonomer incorporations (up to 12.3 mol %). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1122–1132, 2010     

Ethylene homopolymerizaton and copolymerizaton by vanadium(III) complexes containing tridentate or tetradentate iminopyrrolyl ligands

Iminopyrrolyl vanadium(III) complexes 2a–b bearing tridentate ligands [C₄H₃NCH?NC₆H₄L]VCl₂(THF) [L = 2‐P(C₆H₅)₂ ( 2a ), 2‐SMe ( 2b )] and complexes 2c–d with tetradentate ligands [(C₄H₃NCH?N)₂R]VCl(THF) [R = 1,2‐C₆H₄ ( 2c ), 1,2‐C₂H₄ ( 2d )] have been synthesized in high yields. With diethylaluminium chloride as a cocatalyst, complexes 2a–d were investigated as efficient catalysts for ethylene polymerization under various reaction conditions, and exhibited high catalytic activity and remarkable thermal stability. With these complexes, high molecular weight polymers with unimodal molecular weight distributions were obtained, indicating that the polymerization reaction took place in a single‐site nature. Ethylene/1‐hexene copolymerizations were also investigated in the presence of Et₂AlCl. Both increasing ligand denticity and introducing softer atom into the sidearm of the ligands significantly influenced catalytic activity, comonomer incorporation, and the molecular weights of the resultant polymers, suggesting that both the steric and the electronic effects of the ligands played an important role in adjusting chain propagation and transfer rate. The chain transfer mechanisms involved in the copolymerization process were investigated by carefully analyzing the microstructure of the copolymers. The signals of vinyl, disubstituted and tri‐substituted vinylene double bond end groups were detected in the copolymer obtained by 2a /Et₂AlCl system but not in those by 2b–c /Et₂AlCl systems, indicating that bulky electron‐donating group, ? P(C₆H₅)₂, may lead to those unusual transfer reactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of novel cyclic olefin copolymer with high glass transition temperature

A series of novel cyclic olefin copolymers (COCs), including ethylene/tricyclo[4.3.0.1^2,5]deca‐3‐ene (TDE), ethylene/tricyclo[4.4.0.1^2,5]undec‐3‐ene (TUE), and ethylene/tricyclo[6.4.0.1^9,12]tridec‐10‐ene (TTE) copolymers, have been synthesized via effective copolymerizations of ethylene with bulk cyclic olefin comonomers using bis(β‐enaminoketonato) titanium catalysts ( 1a [PhN?C(CH₃)CHC(CF₃)O]₂TiCl₂; 1b : [PhN?C(CF₃)CHC(Ph)O]₂TiCl₂). With modified methylaluminoxane as a cocatalyst, both catalysts exhibit high catalytic activities, producing high molecular weight copolymers with high comonomer incorporations and unimodal molecular weight distributions. The microstructures of obtained ethylene/COCs are established by combination of ¹H, ¹³C NMR, ¹³C DEPT, HSQC ¹H? ¹³C, and ¹H? ¹H COSY NMR spectra. DSC analyses indicate that the glass transition temperature (T_g) increases with the enhancement of comonomer volume (TDE < TUE < TTE). High T_g value up to 180 °C is easily attained in ethylene/TTE copolymer with the low content of 35.8 mol %. TGA analyses reveal that these copolymers all possess high thermal stability with degradation temperatures (T_d) higher than 370 °C in N₂ and air. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3144–3152     

Ethylene–propylene copolymerization with bis(β‐enaminoketonato) titanium complexes activated with modified methylaluminoxane

Ethylene–propylene copolymerization, using [(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂ (R₁ = CF₃, Ph, or t‐Bu; R₂ = CH₃ or CF₃) titanium complexes activated with modified methylaluminoxane as a cocatalyst, was investigated. High‐molecular‐weight ethylene–propylene copolymers with relatively narrow molecular weight distributions and a broad range of chemical compositions were obtained. Substituents R₁ and R₂ influenced the copolymerization behavior, including the copolymerization activity, methylene sequence distribution, molecular weight, and polydispersity. With small steric hindrance at R₁ and R₂, one complex (R₁ = CF₃; R₂ = CH₃) displayed high catalytic activity and produced copolymers with high propylene incorporation but low molecular weight. The microstructures of the copolymers were analyzed with ¹³C NMR to determine the methylene sequence distribution and number‐average sequence lengths of uninterrupted methylene carbons. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5846–5854, 2006     

Ethylene polymerization and ethylene/hexene copolymerization by vanadium(III) complexes bearing bidentate phenoxy‐phosphine oxide ligands

A series of novel vanadium(III) complexes bearing bidentate phenoxy‐phosphine oxide [O,P=O] ligands, (2‐R₁‐4‐R₂‐6‐Ph₂P=O‐C₆H₂O)VCl₂(THF)₂ ( 2a : R₁ = R₂ = H; 2b : R₁ = F, R₂ = H; 2c : R₁ = tBu, R₂ = H; 2d : R₁ = Ph, R₂ = H; 2e : R₁ = R₂ = Me; 2f : R₁ = R₂ = tBu; 2g : R₁ = R₂ = CMe₂Ph) have been synthesized by adding 1 equiv of the ligand to VCl₃(THF)₃ dropwise in the presence of excess triethylamine. Under the same conditions, the adding of VCl₃(THF)₃ to 2.0 equiv of the ligand afforded vanadium(III) complexes bearing two [O,P=O] ligands ( 3c , 3f ). All the complexes were characterized by FTIR and mass spectra as well as elemental analysis. Structures of complexes 2c and 3c were further confirmed by X‐ray crystallographic analysis. On activation with Et₂AlCl and ethyl trichloroacetate, these complexes displayed high catalytic activities for ethylene polymerization (up to 26.4 kg PE/mmol_V·h·bar) even at high reaction temperature (70 °C) indicative of high thermal stability, and produced high molecular weight polymers with unimodal molecular weight distributions. Additionally, the complexes with optimized structure exhibited high catalytic activities for ethylene/1‐hexene copolymerization. Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled in a wide range via the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and reaction temperature. The monomer reactivity ratios r_E and r_H were determined according to ¹³C NMR spectra, which indicated these complexes preferred ethylene to 1‐hexene in the copolymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5298–5306     

Bis(β‐enaminoketonato) vanadium (III or IV) complexes as catalysts for olefin polymerization

Bis(β‐enaminoketonato) vanadium(III) complexes ( 2a–c ) [O(R₁)C?C(H)_xC(R₂)?NC₆H₅]₂VCl(THF) and the corresponding vanadium(IV) complexes ( 3a–c ) [O(R₁)C?C(H)_xC(R₂)? NC₆H₅]₂VO (R₁ = ? (CH₂)₄? , R₂ = H, x = 0, a ; R₁ = ? C₆H₅, R₂ = H, x = 1, b ; R₁ = ? C₆H₅, R₂ = ? C₆H₅, x = 1, c ) have been synthesized from VCl₃(THF)₃ and VOCl₂(THF)₂, respectively, by treating with 2.0 equivalent β‐enaminoketonato ligands in tetrahydrofuran. Structures of 2b and 3a–c were further confirmed by X‐ray crystallographic analysis. The complexes were investigated as the catalysts for ethylene polymerization in the presence of Et₂AlCl. Complexes 2a–c and 3a–c exhibited high catalytic activities (up to 23.76 kg of PE/mmol_V h bar), and afforded polymers with unimodal molecular weight distributions at 70 °C indicating the good thermal stability. The catalytic behaviors were influenced not only by the oxidation state of the catalyst precursors but also by the ligand structures. Complexes 2a–c and 3a–c were also effective catalyst precursors for ethylene/1‐hexene copolymerization. The influence of polymerization parameters such as reaction temperature, Al/V molar ratio and hexene feed concentration on the ethylene/hexene copolymerization behaviors have bee also investigated in detail. In addition, the agents such as AlMe₃, AlⁱBu₃, MeMgBr, MgCl₂, and ZnEt₂ were applied to control the molecular weight and molecular weight distribution modal. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3062–3072, 2010     

Ethylene/α‐olefin copolymerization with bis(β‐enaminoketonato) titanium complexes activated with modified methylaluminoxane

Copolymerizations of ethylene with α‐olefins (i.e., 1‐hexene, 1‐octene, allylbenzene, and 4‐phenyl‐1‐butene) using the bis(β‐enaminoketonato) titanium complexes [(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂ ( 1a : R₁ = CF₃, R₂ = CH₃; 1b : R₁ = Ph, R₂ = CF₃; and 1c : R₁ = t‐Bu, R₂ = CF₃), activated with modified methylaluminoxane as a cocatalyst, have been investigated. The catalyst activity, comonomer incorporation, and molecular weight, and molecular weight distribution of the polymers produced can be controlled over a wide range by the variation of the catalyst structure, α‐olefin, and reaction parameters such as the comonomer feed concentration. The substituents R₁ and R₂ of the ligands affect considerably both the catalyst activity and comonomer incorporation. Precatalyst 1a exhibits high catalytic activity and produces high‐molecular‐weight copolymers with high α‐olefin insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6323–6330, 2005     

Olefin polymerization and copolymerization by complexes bearing [ONNO]‐Type salan ligands: Effect of ligand structure and metal type (titanium,zirconium, and vanadium)

A series of novel titanium(IV) complexes bearing tetradentate [ONNO] salan type ligands: [Ti{2,2′‐(OC₆H₃‐5‐t‐Bu)₂‐NHRNH}Cl₂] (Lig¹TiCl₂: R = C₂H₄; Lig²TiCl₂: R = C₄H₈; Lig³TiCl₂: R = C₆H₁₂) and [Ti{2,2′‐(OC₆H₂‐3,5‐di‐t‐Bu)₂‐NHC₆H₁₂NH}Cl₂] (Lig⁴TiCl₂) were synthesized and used in the (co)polymerization of olefins. Vanadium and zirconium complexes: [ M{2,2′‐(OC₆H₃‐3,5‐di‐t‐Bu)₂‐NHC₆H₁₂NH}Cl₂] (Lig⁴VCl₂: M = V; Lig⁴ZrCl₂: M = Zr) were also synthesized for comparative investigations. All the complexes turned out active in 1‐octene polymerization after activation by MAO and/or Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄]. The catalytic performance of titanium complexes was strictly dependent on their structures and it improves for the increasing length of the aliphatic linkage between nitrogen atoms (Lig¹TiCl₂ << Lig²TiCl₂ < Lig³TiCl₂) and declines after adding additional tert‐Bu group on the aromatic rings (Lig³TiCl₂ < Lig⁴TiCl₂). The activity of all titanium complexes in ethylene polymerization was moderate and the properties of polyethylene was dependent on the ligand structure, cocatalyst type, and reaction conditions. The Et₂AlCl‐activated complexes gave polymers with lover molecular weights and bimodal distribution, whereas ultra‐high molecular weight PE (up to 3588 kg mol^?1) and narrow MWD was formed for MAO as a cocatalyst. Vanadium complex yielded PE with the highest productivity (1925.3 kg mol_v^?1), with high molecular weight (1986 kg mol^?1) and with very narrow molecular weight distribution (1.5). Copolymerization tests showed that titanium complexes yielded ethylene/1‐octene copolymers, whereas vanadium catalysts produced product mixtures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2111–2123     

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     

Homo‐ and copolymerization of norbornene derivatives with ethene by ansa‐fluorenylamidodimethyltitanium activated with methylaluminoxane

(t‐BuNSiMe₂Flu)TiMe₂ ( 1 ) activated with Me₃Al‐free methylaluminoxane (dried MAO) which conducts vinyl addition polymerization of norbornene (N) with very high activity was applied for homopolymerization of N derivatives (i.e., 5‐vinyl‐2‐norbornene (5V2N), 5‐ethylidene‐2‐norbornene (5E2N), dicyclopentadiene (DCPD)) at 40 °C. The activities for the N derivatives were about two orders of magnitude lower than that for N and decreased in the following order: 5E2N ? 5V2N ? DCPD. Copolymerization of ethene (E) and 5E2N under an atmospheric pressure of E was then conducted by 1 ‐dried MAO. The copolymerization proceeded with better activity than the homopolymerization of 5E2N and gave poly(E‐co‐5E2N) with narrow molecular weight distribution. The content of the ethylidene group in poly(E‐co‐5E2N) was controlled by the feed ratio of 5E2N/E. The T_g value of the copolymer changed from 70 °C to 155 °C according to the 5E2N content from 27 mol % to 68 mol %. The addition of N as a third monomer to the E‐5E2N copolymerization improved the activity and raised the T_g values of the terpolymer above 200 °C. The content of 5E2N was controlled by the 5E2N/N ratio with keeping the high T_g values. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4581–4587, 2007     

Copolymerization of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes

The copolymerizations of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes {[(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂; R₁ = CF₃ and R₂ = CH₃ for 1a , R₁ = Ph and R₂ = CF₃ for 1b ; and R₁ = t‐Bu and R₂ = CF₃ for 1c } activated with modified methylaluminoxane (MMAO) as a cocatalyst were investigated. High‐molecular‐weight copolymers with cis‐1,2‐cyclopentene units were obtained. The catalyst activity, cyclopentene incorporation, polymer molecular weight, and polydispersity could be controlled over a wide range through the variation of the catalyst structure and reaction parameters, such as the Al/Ti molar ratio, cyclopentene feed concentration, and polymerization reaction temperature. The complex 1b /MMAO catalyst system exhibited the characteristics of a quasi‐living ethylene polymerization and an ethylene–cyclopentene copolymerization and allowed the synthesis of polyethylene‐block‐poly(ethylene‐co‐cyclopentene) diblock copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1681–1689, 2005     

Living copolymerization of ethylene with norbornene mediated by heteroligated (Salicylaldiminato)(β‐enaminoketonato)titanium catalysts

Three heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH?N(C₆F₅)][(p‐XC₆H₄)N?C(Bu^t)CHC(CF₃)O]TiCl₂ ( 3a : X = F, 3b : X = Cl, 3c : X = Br) were synthesized and investigated as the catalysts for ethylene polymerization and ethylene/norbornene copolymerization. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts exhibited high activities toward ethylene polymerization, similar to their parallel parent catalysts. Furthermore, they also displayed favorable ability to efficiently incorporate norbornene into the polymer chains and produce high molecular weight copolymers under the mild conditions, though the copolymerization of ethylene with norbornene leads to relatively lower activities. The sterically open structure of the β‐enaminoketonato ligand is responsible for the high norbornene incorporation. The norbornene concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. When the norbornene concentration in the feed is higher than 0.4 mol/L, the heteroligated catalysts mediated the living copolymerization of ethylene with norbornene to form narrow molecular weight distribution copolymers (M_w/M_n < 1.20), which suggested that chain termination or transfer reaction could be efficiently suppressed via the addition of norbornene into the reaction medium. Polymer yields, catalytic activity, molecular weight, and norbornene incorporation can be controlled within a wide range by the variation of the reaction parameters such as comonomer content in the feed, reaction time, and temperature. ©2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6072–6082, 2009     

Vanadium complex with tetradentate [O,N,N,O] ligand supported on magnesium type carrier for ethylene homopolymerization and copolymerization

Immobilization of 1,2‐cyclohexylenebis(5‐chlorosalicylideneiminato)vanadium dichloride on the magnesium support obtained in the reaction of MgCl₂·3.4EtOH with Et₂AlCl gives a highly active precursor for ethylene homopolymerization and its copolymerization with 1‐octene. This catalyst exhibits the highest activity in conjunction with MAO, but it is also highly active with AlMe₃ as a cocatalyst. On the other hand, when combined with chlorinated alkylaluminum compounds, Et₂AlCl and EtAlCl₂, it gives traces of polyethylene. Moreover, its catalytic activity is strongly affected by the reaction temperature: it increased with rising polymerization temperature from 20 °C to 60 °C. The kinetic curves obtained for the supported vanadium catalyst, in contrast to its titanium analogue, are of decay type, yet the reduction in the polymerization rate is rather moderate in the early stages of polymerization, and then it is relatively very slow. The vanadium catalyst gives copolymers at a lower yield than the titanium one does, but with the significantly higher 1‐octene content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 471–478, 2010     

Quasi‐living copolymerization of ethylene with 1‐hexene by heteroligated (salicylaldiminato β‐enaminoketonato) titanium complexes

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH = N(C₆F₅)] [PhN = C(R₁)CHC(R₂)O]TiCl₂ [ 3a : R₁ = CF₃, R₂ = ^tBu; 3b : R₁ = Me, R₂ = CF₃; 3c : R₁ = CF₃, R₂ = Ph; 3d : R₁ = CF₃, R₂ = C₆H₄Ph(p ); 3e : R₁ = CF₃, R₂ = C₆H₄Ph(o ); 3f : R = CF₃, R₂ = C₆H₄Cl(p ); 3g : R₁ = CF₃; R₂ = C₆H₃Cl₂(2,5); 3h : R₁ = CF₃, R₂ = C₆H₄Me(p )] were investigated as catalysts for ethylene (co)polymerization. In the presence of modified methylaluminoxane as a cocatalyst, these complexes showed activities about 50%–1000% and 10%–100% higher than their corresponding bis(β‐enaminoketonato) titanium complexes for ethylene homo‐ and ethylene/1‐hexene copolymerization, respectively. They produced high or moderate molecular weight copolymers with 1‐hexene incorporations about 10%–200% higher than their homoligated counterpart pentafluorinated FI‐Ti complex. Among them, complex 3b displayed the highest activity [2.06 × 10⁶ g/mol_Ti?h], affording copolymers with the highest 1‐hexene incorporations of 34.8 mol% under mild conditions. Moreover, catalyst 3h with electron‐donating group not only exhibited much higher 1‐hexene incorporations (9.0 mol% vs. 3.2 mol%) than pentafluorinated FI‐Ti complex but also generated copolymers with similar narrow molecular weight distributions (M _w/M _n = 1.20–1.26). When the 1‐hexene concentration in the feed was about 2.0 mol/L and the hexene incorporation of resultant polymer was about 9.0 mol%, a quasi‐living copolymerization behavior could be achieved. ¹H and ¹³C NMR spectroscopic analysis of their resulting copolymers demonstrated the possible copolymerization mechanism, which was related with the chain initiation, monomer insertion style, chain transfer and termination during the polymerization process. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2787–2797