Titanium Dichloride Complexes Research Articles

Silica-supported catalyst for the synthesis of low entangled UHMWPE suitable for solid-state processing

Different types of silica (mesoporous, spherical and nano-size particles), pre-activated with methylaluminoxane (MAO), are used to activate and support the bis[N-(3‑tert-butylsalicydene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride (FI) complex with the aim to synthesize low-entangled UHMWPE having controlled particle morphology. Through the porosity analysis, nitrogen adsorption and desorption isotherms, a decreased surfaced area of the chosen silica is observed when supported by MAO. From the bonding energy study by XPS, the bonding energy difference of Si and O, between the nano-size silica and in the MAO-nano silica, suggests the formation of Al-O-Si after chemical activation with MAO. Using elementary analysis, ICP-OES and XPS characterization, the aluminum content grafted on the silica surface is found to match with the anticipated amount of MAO on the MAO-Silica/FI catalytic system, indicating a stable grafting after catalyst supporting. From the rheological studies of the polymers, coupled with DSC results using an isothermal crystallization protocol, the resultant entangled state in the semi-crystalline polymers is estimated. The observations are that the entangled state achieved during polymerization from the investigated heterogeneous catalytic systems, is the lowest in PE-MAO-nano silica/FI, increases in PE-MAO-mesoporous silica/FI and is highest in PE-MAO-spherical silica/FI. Silica modification using two different silanes shows significant influence on the catalytic activity, giving lower polymer yield in MAO-modified-mesoporous silica and MAO-modified-nano silica compared to the unmodified MAO-silica. Whereas, no significant spatial effect is observed in the formation of chain entanglement, showing the increased entanglement density of the nascent polymers. By employing heterogeneous catalytic systems, reactor fouling and wall sheeting problems are resolved and the polymers show good morphology replication of the support. The UHMWPE synthesized using the nano silica as support, having the lowest entangled state and loosely packed crystals, can be uniaxially processed in the solid-state to a thin tape having thickness around 34 μm, showing maximum tensile strength of 3.26 N/tex and tensile modulus of 170 N/tex.

Influence of diverse MgClx/R’nClmAly(OR)z activators/supports in tailoring of entangled state of UHMWPE

Heterogeneous MgClx/EtnAly(2-ethyl-1-hexoxide)z dual activator/support, together with bis[N-(3‑tert-butylsalicylidene)pentafluoroanilinato] titanium(IV) dichloride complex, has demonstrated its potential in the synthesis of low entangled UHMWPE under controlled polymerization conditions. The work was corroborated with the solid-state processed uniaxial tapes having ultimate mechanical properties, which were found at par with the polymer synthesized using homogeneous catalysis with the edge to govern nascent polymer morphology. The activator/support is tuned depending on the combination of aluminum-alkyls and alcohols employed in the synthesis. Herein, a series of alcohols (2-ethyl-1-hexanol, 3-methyl-1-butanol, n-butanol, n-pentanol, n-octanol, cyclohexanol, and benzyl alcohol) and phenol are employed in the formation of the MgCl2/ROH adduct followed by reaction with different aluminum-alkyls (TEA, DEAC, TiBAl, and TMA) to form a diverse class of MgClx/R’nClmAly(OR)z activators/supports. The diverse activators are employed in the synthesis of low-entangled UHMWPE, the resultant polymers display controlled fine particle morphology without any reactor fouling/wall sheeting. The characteristics of the synthesized polymers are studied using SEM, DSC, melt rheology, high-temperature NMR, and FT-IR. All the synthesized polymers are found to be linear UHMWPE having a reduced number of entanglement, making them suitable (with exceptions) for solvent-free solid-state processing to produce high-strength and modulus tapes. An attempt is made to illustrate the varying entanglement state by correlating the nascent UHMWPE characteristics (such as particle morphology, particulate density, single crystal lamellae structures, storage modulus build-up, and advanced thermal analysis) with the solid-state processing. The resultant catalytic systems of the type Cat. 1/MgClx/R’nClmAly(OR)z are found to form unique nano dual activator/support, crucial for the supporting of a small number of active sites, thus reducing chain overlap during the polymer synthesis. The developed catalytic systems allow tailoring the molecular weight from 3 to 43 million g/mol and Ð from 3.3 to 38 of the synthesized polymers. The mechanical properties are found to be ∼ 4 N/tex of specific strength and > 200 N/tex of specific modulus.

Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution†

Comprehensive SummaryA series of titanium amido complexes (1‐Ti(NMe2)2 to 4‐Ti(NMe2)2) bearing NNO‐tridentate ligands was synthesized from the reactions of phenoxy‐imine‐amine ligands with one equivalent of Ti(NMe2)4. Subsequently, titanium dichloride complexes (1‐TiCl2 to 4‐TiCl2) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2‐Ti(NMe2)2, 2‐TiCl2, and 4‐TiCl2 in the solid state were determined by single‐crystal X‐ray diffraction. Upon activation with MAO, titanium dichloride complexes as single‐site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3‐TiCl2/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 104 g∙mol−1) and very narrow distribution (Đ = 1.23). In the presence of 1‐octene as comonomer, linear low‐density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 104 g∙mol−1) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.

Highly active titanium(IV) dichloride FI catalysts bearing a diallylamino group for the synthesis of disentangled UHMWPE

A family of 16 salicylaldarylimine titanium(IV) dichloride complexes bearing diallylamino group, namely {2‐[3‐ or 4‐(CH2CHCH2)2NC6H4NCH]‐6‐R1‐4‐R2‐C6H2O}2TiCl2 (R1 = t‐Bu, CMe2(Ph); R2 = H, Me, OMe, t‐Bu) have been used for polymerization of ethylene in the presence of methylaluminoxane. The effects of reaction conditions on the polymerization were examined in detail. All the pre‐catalyst are highly active (up to 14.0 × 106 g(PE) mol(Ti)−1 −1 h−1) for ethylene polymerization at 30°С to 60°С with the activities and MM correlating with the R1‐substituent type and position of NAll2‐group: CMe2(Ph) > t‐Bu and meta‐NAll2 > para‐NAll2 for any R2. Highly linear polyethylenes (Tm's as high as 141.0°С) can be obtained with high molecular weights in the range 0.70 to 4.10 × 106 g mol−1 with disentangled morphology, suitable for technologically more advanced and greeny way to produce high‐modulus high‐strength fibers of ultrahigh molecular weight polyethylene via solid‐state (solvent‐free) deformation processing.

Synthesis and characterization of isotactic poly(p-hydroxystyrene)- block-1,4-trans-polybutadiene by sequential monomer addition using titanium complex with an [OSSO]-type Bis(phenolate) ligand

Herein, we demonstrated the synthesis and characterization of a well-defined diblock copolymer consisting of isotactic poly(p-hydroxystyrene) (iP(p-HOS)) and 1,4-trans-polybutadiene (1,4-trans-PBD), iP(p-HOS)-b-1, 4-trans-PBD, by the combination of sequential monomer addition and deprotection. Isospecific living polymerization of p-tert- butyldimethylsilyloxystyrene and living trans-1,4-polymerization of 1,3-butadiene were catalyzed by 1, 4-dithiabutandiyl-2, 2ʹ-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by methylaluminoxane (MAO) at room temperature to provide highly stereospecific isotactic poly(p-tert-butyldimethylsilyloxystyrene) (iP(p-TBDMSOS)) and 1,4-trans-polybutadiene (1,4-trans-PBD) with narrow molecular weight distribution. Furthermore, the iP(p-TBDMSOS)-b-1, 4-trans-PBD was prepared via sequential monomer addition in the presence of complex 1 and MAO. The deprotection of the iP(p-TBDMSOS) block was promoted by concentrated hydrochloric acid to produce iP(p-HOS)-b-1, 4-trans-PBD. In addition, the resultant diblock copolymer and intermediate polymers were characterized by gel permeation chromatography, nuclear magnetic resonance and differential scanning calorimeter.

Synthesis and self-assembly of a novel amphiphilic diblock copolymer consisting of isotactic polystyrene and 1,4-trans-polybutadiene-graft-poly(ethylene oxide).

Herein, a novel amphiphilic diblock copolymer consisting of isotactic polystyrene (iPS) and 1,4-trans-polybutadiene-graft-poly(ethylene oxide) (1,4-trans-PBD-g-PEO), iPS-b-(1,4-trans-PBD-g-PEO), was synthesized by the combination of living coordination copolymerization and graft copolymerization. iPS-b-1,4-trans-PBD was firstly synthesized via sequential monomer addition in the presence of 1,4-dithiabutandiyl-2,2′-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by triisobutyl aluminum modified methylaluminoxane (MMAO). Moreover, hydroboration of double bonds in the 1,4-trans-PBD blocks were performed with 9-borabicyclo[3.3.1]nonane (9-BBN) and subsequent oxidation by NaOH/H2O2 to form hydroxyls. Consequently, PEO was grafted into the hydroxylated 1,4-trans-PBD block in terms of ring-opening polymerization of ethylene oxide with potassium/naphthalide as initiatior. We also described solvent-evaporation-induced self-assembly of iPS-b-1,4-trans-PBD in n-dodecane and iPS-b-1,4-trans-PBD-g-PEO in aqueous solution, which were selective solvent for 1,4-trans-PBD and for 1,4-trans-PBD-g-PEO blocks, respectively. In these cases, tetrahydrofuran (THF) was used as good and volatile solvent. These resultant iPS-containing diblock copolymers could self-assemble into spherical nano-micelles with an iPS core as amorphous agglomeration or a very low degree of crystallinity resulting from slow crystallization rate and nanoconfinement. In addition, after isothermal crystallization of iPS in the micellar cores self-assembled in n-dodecane at 120 °C for 3 hours, the micellar morphology changed from sphere-like to platelet-like. It was believed that isothermal crystallization of iPS induced the deformation of the micelles.

Synthesis of isotactic polystyrene-block-polyethylene by the combination of sequential monomer addition and hydrogenation of 1,4-trans-polybutadiene block

Herein, we demonstrate the synthesis of a well-defined diblock copolymer consisting of isotactic polystyrene (iPS) and linear polyethylene, isotactic polystyrene-block-polyethylene (iPS-b-PE), by the combination of sequential monomer addition and hydrogenation. Isospecific living polymerization of styrene and living trans-1,4-polymerization of 1,3-butadiene were catalyzed by 1,4-dithiabutandiyl-2,2′-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by triisobutyl aluminum modified methylaluminoxane (MMAO) at room temperature to provide highly isotactic polystyrene (iPS) and 1,4-trans-polybutadiene (1,4-trans-PBD) with narrow molecular weight distribution. Furthermore, the iPS-b-1,4-trans-PBD was synthesized via sequential monomer addition in the presence of complex 1 and MMAO. The hydrogenation of the 1,4-trans-PBD block was promoted by RuCl2(PPh3)3 used as a catalyst to produce iPS-b-PE.

Novel diamine-bis(phenolate) Ti(IV) complexes – tuning the complex structure to control catalytic properties in α-olefin polymerization

Four monomeric titanium(IV) dichloride complexes of amine-bis(phenolate) ligands having an extra donor arm (2a–2d) and one oxo-bridged complex 3 were successfully synthesized in the reaction of TiCl4 with a sodium salt of the appropriate ligand, and they were characterized by 1H NMR spectroscopy. The ligands had either a dimethylamino side‐arm donor and t-Bu substituents on both (1a) and one (1d) phenolate rings or a diisopropylamino side-arm donor and t-Bu (1b) and t-Bu along with OMe (1c) phenolate substituents. All complexes upon activation with [Ph3CB(C6F5)4] and MAO were used to catalyze polymerization of 1-octene (in liquid monomer) into poly(1-octene). Their activities as well as product microstructures were found to be highly dependent on the structure of the diamine-bis(phenolate) ligand. The catalytic activities of the complexes towards 1-olefin polymerization decreased in the following order: 2a>>2b>2c>2d. The polymers produced were atactic or isotactic with the [mmmm] pentad content varied from about 4 up to 90%. The highest isotacticity was exhibited by poly(1-octene) synthesized by 2d. The catalytic activities increased and polymer molecular weight decreased with the increasing reaction temperature. Moreover, catalyst 2a/Al(iBu)3Ph3CB(C6F5)4 was used in the bulk polymerization of other α-olefin and it was found that the monomer conversion decrease in the order: 1-octene>1-decene>1-dodecene>1-hexene>>4-methyl-1-pentene.

Activity of phenoxy-imine titanium catalysts in ethylene polymerization: A quantum chemical approach

The mechanism of ethylene polymerization on phenoxy-imine (FI) titanium catalysts was studied theoretically to identify the major factors affecting the catalytic activity. Geometry optimizations of FI ligands, octahedral titanium dichloride complexes, active cationic species, and their π‐complexes with ethylene as well as calculations of the energy profile of chain propagation were performed at the BP86-D3 level. We found that the calculated energy gaps between frontier orbitals (HOMO and LUMO) in the active cations of the catalysts correlate with the experimental activity values. High activities of FI catalysts with α‐Cumyl groups were attributed to smaller HOMO-LUMO gaps due to hyperconjugation between π-systems of α‐Cumyl and (N‐aryl)salicylaldimine moieties in the active cations. The correlation provides a qualitative estimate of the catalytic activity for further design of new FI titanium complexes.

Synthesis of Imidazolin-2-iminato Titanium Complexes Containing Aryloxo Ligands and Their Catalytic Performance in the Polymerization of α-Olefins

The synthesis of mixed (aryloxo)(imidazolin-2-iminato)titanium dichloride complexes is presented. Full characterization of the complexes, including solid-state X-ray diffraction analysis of four complexes, is reported. Their catalytic activity in the polymerization of ethylene, propylene, 1-hexene, and 1-octene was studied. The different substituents at the aryloxo moiety were found to have a substantial impact on the reactivity of the complexes, indicating the need for a balance of steric and electronic effects. The complex (1,3-di-tert-butylimidazolin-2-iminato)(2,6-di-tert-butyl-4-methylphenoxide)titanium dichloride (1) was found to be the most active in the polymerization of ethylene, whereas the complex (1,3-di-tert-butylimidazolin-2-iminato)(2,6-di-tert-butylphenoxide)titanium dichloride (2) was found to be the most active in the polymerization of propylene. Interestingly, all complexes were more active in the polymerization of propylene than in that of ethylene.

Synthesis of half-titanocenes containing 1,3-imidazolidin-2-iminato ligands of type, Cp*TiCl2[1,3-R2(CH2N)2CN]: highly active catalyst precursors in ethylene (co)polymerisation

Cp*TiCl2[1,3-(2,6-Me2C6H3)2(CH2N)2CN] showed remarkable catalytic activities for ethylene/1-hexene copolymerisation with efficient comonomer incorporation (ex. activity 1 750 000 kg-polymer per mol-Ti per h).

Homo- and Heteroligated Salicylaldiminato Titanium Complexes with Different Substituents Ortho to the Phenoxy Oxygens for Ethylene and Ethylene/1-Hexene (Co)polymerization

A series of homoligated (1c–1e) and heteroligated (2a–2e) salicylaldiminato titanium dichloride complexes with different substituents ortho to the phenoxy oxygens were efficiently prepared. X-ray diffraction studies on these new dichloride complexes 2b, 2d, and 2e reveal a distorted octahedral coordination of the central metal. In the presence of dried methylaluminoxane, all the complexes exhibit high ethylene polymerization productivities. Surprisingly, complex 1d incorporating an o-(trimethylsilyl)ethynyl group displays the highest activity [5.26 × 103 kg of polyethylenes (mol Ti)−1 h–1]. In ethylene/1-hexene copolymerization, the heteroligated complexes 2a–2e display improved activities and intermediate incorporation ability compared with their homoligated counterparts 1a–1f. The activity and incorporation ability for 1-hexene are highly dependent on the nature of the ortho-substituents. Among them, (trimethylsilyl)ethynyl-substituted precatalyst (1d) achieves the highest incorporation ratio (27.3 mol %), while ethynyl-substituted precatalyst (2c) achieves the highest copolymerization activity [2.89 × 103 kg of copolymers (mol Ti)−1 h–1].

Crystallization behavior of ultrahigh‐molecular‐weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites prepared by ethylene in situ polymerization

ABSTRACTA [3‐t‐Bu‐2‐OC6H3CHN(C6F5)]2TiCl2 catalyst (bis(phenoxyimine)titanium dichloride complex – FI catalyst) was immobilized on disilanolisobutyl polyhedral oligomeric silsesquioxane (OH‐POSS) to prepare ultrahigh molecular‐weight polyethylene (UHMWPE)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites during ethylene in situ polymerization. The dispersion state of POSS in the UHMWPE matrix was characterized by X‐ray diffraction measurements and transmission electron microscopy. It was shown that the OH‐POSS achieved uniformed dispersion in the UHMWPE matrix, although its polarity was unmatched. The isothermal and nonisothermal crystallization behavior of the nanocomposites was investigated by means of differential scanning calorimetry. The crystallization rate of the nanocomposites was enhanced because of the incorporation of POSS during the isothermal crystallization. POSS acted as a nucleus for the initial nucleation and the subsequent growth of the crystallites. For nonisothermal studies, POSS showed an increase in the crystallinity. The crystallization rate of the nanocomposites decreased because the presence of POSS hindered the crystal growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40847.

Titanium (IV) and zirconium (IV) chloride complexes on the base of chiral tetraaryl-1,3-dioxolane-4,5-dimetanol ligands in the polymerization of ethylene: The promoting role of lithium and magnesium chloride

Coordination compounds of titanium (IV) and zirconium (IV) with tetra-aryl-1,3-dioxolan-4,5-dimethanol (1,2) derivatives were synthesized and characterized by NMR- and IR-spectroscopy and X-ray crystallography. It was demonstrated that titanium dichloride complexes (5–6, 9–12) when treated with MAO, TMA or TIBA are inactive in ethylene polymerization catalysis. However, these compounds become catalytically active in presence of lithium or magnesium chlorides. It was found that the magnitude of the resulting catalytic activity correlates with the following factors: mode of non-transition metals chlorides introduction to the reaction mixture, the nature of activator, and its overall amount. Resulting catalytic activity varied between 54 and 3500 kg PE/mole Ti٠h٠bar. Formed polymer was a linear polyethylene of high and ultrahigh molecular weight (over 5.95 105 g/mole) with high polydispersity index. Possible mechanisms of lithium and magnesium chlorides ability to promote the catalytic process were proposed.

Mechanism of Isotactic Styrene Polymerization with a C6F5-Substituted Bis(phenoxyimine) Titanium System

We report a combined, experimental and theoretical, study of styrene polymerization to clarify the regio- and stereocontrol mechanism operating with a C6F5-substituted bis(phenoxyimine) titanium dichloride complex. Styrene homopolymerization, styrene–propene and styrene–ethene–propene copolymerizations have been carried out to this aim. A combination of 13C NMR analysis of the chain-end groups and of the microstructure of the homopolymers and copolymers reveals that styrene polymerization is highly regioselective and occurs prevalently through 2,1-monomer insertion. DFT calculations evidenced that steric interaction between the growing chain and the monomer in the transition state insertion stage is at the origin of this selectivity. The formation of isotactic polystyrene with a chain-end like microstructure is rationalized on the base of a mechanism similar to that proposed for the syndiospecific propene polymerization catalyzed by bis(phenoxyimine) titanium dichloride complexes. Finally, a general stereocontrol mechanism operative in olefin polymerization with this class of complexes is proposed.

Bis(1,3-di-tert-butylimidazolin-2-iminato) Titanium Complexes as Effective Catalysts for the Monodisperse Polymerization of Propylene

The use of bis(1,3-di-tert-butylimidazolin-2-iminato) titanium dichloride (1) and dimethyl (2) complexes in the polymerization of propylene is presented. The complexes were activated using different amounts of methylalumoxane (MAO), giving in each case a very active catalytic mixture and producing polymers with a narrow molecular weight distribution (polydispersity = 1.10). The use of the cocatalyst triphenylcarbenium (trityl) tetra(pentafluorophenyl)borate totally inhibits the reaction, producing the corresponding bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(III) methyl complex, the trityl radical ((•)CPh(3)), the anionic MeB(C(6)F(5))(4)(-), B(C(6)F(5))(3), and the bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(IV) dimethyl·B(C(6)F(5))(3) complex. The use of a combination of physical methods such as NMR, ESR-C(60), and MALDI-TOF analyses enabled us to propose a plausible mechanism for the polymerization of propylene, presenting that the polymerization is mainly carried out in a living fashion. In addition, we present a slow equilibrium toward a small amount of a dormant species responsible for 2,1-misinsertions and chain transfer processes.

Polymerization of higher α-olefins with the catalytic system (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-bis(perfluorophenyldimethanolate) titanium(IV) dichloride-organoaluminum compound

The catalytic activity of the titanium(IV) dichloride complex with the (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-bis(perfluorophenyldimethanol) ligand in the presence of a cocatalyst (polymethylaluminoxane, triethylaluminum, or triisobutylaluminum) in the polymerization of higher α-olefins (1-hexene, 1-octene, 1-decene) is investigated. It is shown that, depending on the types of cocatalyst and monomer and the molar ratio of components of the catalytic system, high- or ultrahigh-molecular-mass poly(α-olefins) with Mw = (4 × 105)−(3 × 106) can be prepared. The chain microstructure of polyhexene is examined.

Easy and Selective Method for the Synthesis of Various Mono-O-functionalized Calix[4]arenes: De-O-functionalization Using TiCl4

An efficient and selective method for the monofunctionalization of p-tert-butylcalix[4]arene is described. A mono-de-O-functionalization of disubstituted p-tert-butylcalix[4]arenes using titanium tetrachloride was developed to synthesize a series of monosubstituted p-tert-butylcalix[4]arenes with the pendant functions being ethoxycarbonylmethyloxy, 3-ethoxycarbonylpropyloxy, cyanomethyloxy, 3-cyanopropyloxy, 4-bromobutyloxy, 3-hydroxypropyloxy, propyloxy, 2-methylpropyloxy, 3-butynyloxy, and 3-cyanopropyloxy groups. The reaction mechanism of the formation of 5,11,17,23-tetra-tert-butyl-26,27,28-trihydroxy-25-(3-ethoxycarbonylpropyloxy) calix[4]arene was studied by (1)H NMR and GC/mass spectroscopy monitoring. Reaction of TiCl4 with the disubstituted p-tert-butylcalix[4]arene produced the corresponding dioxocalix[4]arene titanium dichloride complex, which undergoes elimination of ethyl 4-chlorobutyrate, leading to a trioxocalix[4]arene titanium dichloride complex and to monosubstituted calix[4]arene after hydrolysis. These two complexes were also synthesized, isolated, and fully characterized.

ChemInform Abstract: Asymmetric Epoxidation of Unfunctionalized Alkenes Using the New C2- Symmetrical 1,1′-Binaphthyl-2,2′-dimethylene-Bridged ansa-Bis(1- indenyl)titanium Dichloride Catalyst.

Abstract The asymmetric catalytic epoxidation of various unfunctionalized alkyl and aryl alkenes has been accomplished using the new C 2 -symmetrical 1,1′-binaphthyl-2,2′-dimethylene-bridged ansa -Bis(1-indenyl)titanium dichloride complex. Enantiomeric excesses of 22% and activities up to 61 turnovers were observed using the (R)(−)-BpDM-(1-ind) 2 TiCl 2 catalyst.

Effect of cocatalysts on ethylene polymerization with fluorinated bisphenoxyimine titanium as a catalyst

AbstractIn this study, we examined various alkylaluminums, including triethylaluminum (TEA), triisobutylaluminum (TIBA), and diethylaluminum chloride (DEAC), as cocatalysts for the activation of ethylene polymerizations in the presence of a fluorinated Fujita group invented titanium (FI‐Ti) catalyst, bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato] titanium(IV) dichloride (complex 1). DEAC, because of the strong Lewis acidity, was an efficient cocatalyst for activating complex 1 for the ethylene polymerizations, whereas TEA and TIBA as cocatalysts could hardly polymerize ethylene. The effects of the polymerization temperature and Al/Ti molar ratio on the formation of active species, properties, and molecular weight of the resulting polyethylene were investigated. In the complex 1/DEAC catalyst system, the oxidation states of Ti active species were determined by electron paramagnetic resonance. The results demonstrated that Ti(IV) active species were inclined to polymerize ethylene and yielded high‐molecular‐weight polyethylene. Comparatively, Ti(III) active species resulted from the reduction of Ti(IV) by DEAC and afforded oligomers. Moreover, the bigger steric bulk for the cocatalysts was necessary to achieve ethylene living polymerization with the fluorinated FI‐Ti catalyst. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011