MAO Cocatalyst Research Articles

The Effect of SiMe3 and SiEt3 Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide-Modified Half-Titanocenes.

Remarkable effects of SiMe3 and SiEt3 para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl2 (O-2,6-i Pr2 -4-R-C6 H2 ) [R=SiMe3 (6), SiEt3 (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81×105 kg-polymer mol-1 -Ti h, Mn =6.55-10.0×104 , DC-OH 2.3-3.6 mol %).

The Effect of SiMe3 and SiEt3Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide‐Modified Half‐Titanocenes

AbstractRemarkable effects of SiMe3 and SiEt3 para‐substituents in the phenoxide‐modified half‐titanocenes, Cp*TiCl2(O‐2,6‐iPr2‐4‐R‐C6H2) [R=SiMe3 (6), SiEt3 (7)], toward the catalytic activities in ethylene copolymerizations with 2‐methyl‐1‐pentene, 1‐decene, 1‐dodecene and with 9‐decen‐1‐ol (DC‐OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high‐molecular‐weight (HMW) ethylene copolymers incorporating DC‐OH (or 5‐hexen‐1‐ol, HX‐OH) has been attained in the copolymerization by 7, which showed better DC‐OH (HX‐OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene‐co‐DC‐OH)s, with high activities (activity 1.21–3.81×105 kg‐polymer mol−1‐Ti h, Mn=6.55–10.0×104, DC‐OH 2.3–3.6 mol %).

Finely Tuned α,α′-Bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridine-Based Practical Iron Precatalysts for Targeting Highly Linear and Narrow Dispersive Polyethylene Waxes with Vinyl Ends

One-pot template construction of α,α′-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl iron chlorides achieved by reacting α,α′-dioxo-2,3:5,6-bis(pentamethylene)pyridine and the corresponding anilines along with the respective iron chloride in acetic acid provided yields of 26–76%. All these complexes were characterized by FT-IR, elemental analysis, 1H NMR, and X-ray diffraction analysis. Distorted-square-pyramidal geometries are observed in the molecular structures of Fe1 and Fe6, respectively. When MAO or MMAO is used as a cocatalyst, Fe1–Fe5 display a high activity of 107 g with highly linear, low-molecular-weight, and narrow-polydispersity polyethylenes (PEs) being obtained by ethylene polymerization. The catalytic activity of Fe1 reached a maximum activity ((3.81–3.93) × 107 g of PE (mol of Fe)−1 h–1) by using the cocatalyst MAO or MMAO at Al/Fe ratio of 5000. All of the synthesized iron precatalysts Fe1–Fe8 containing sterically ortho benzhydryl and aryl (2,4,6-substituents of the aryl ring) groups...

Ethylene oligomerization reactions catalyzed by homogeneous and silica immobilized NˆO Fe(II) and Co(II) complexes

Treatment of 2-phenyl-2-((3(triethoxysilyl)propyl)imino)ethanol (L1) and 4-nitro-2-((3(triethoxysilyl)propyl)imino)methyl)phenol (L2) with MCM-41 support afforded the respective immobilized ligands (L1im) and (L2im). Reactions of synthons L1, L2, L1im and L2im with either FeCl2·4H2O or CoCl2 led to the formation of their respective homogeneous and immobilized metal complexes [Fe(L1)2] (Fe1), [Co(L1)2] (Co1), [Fe(L2)2] (Fe2), [Co(L2)2] (Co2), [Fe(L1im)2] (Fe1im), [Co(L1im)2] (Co1im), [Fe(L2im)2] (Fe2im), and [Co(L2im)2] (Co2im). The compounds were characterized by FT-IR, NMR, ESI-MS, SEM-EDX and elemental analysis. Activation of the Fe(II) and Co(II) complexes with EtAlCl2, resulted in active catalysts for the tandem ethylene dimerization and Friedel-Crafts alkylation of the toluene solvent to produce mainly alkyltoluenes. On the other hand, the use of chlorobenzene solvent and MAO co-catalyst led to the formation of mainly butenes. Generally, the immobilized catalysts exhibited lower catalytic activities, but with comparable selectivity to the homogeneous catalysts. Recycling studies established that the immobilized catalysts were active for three runs without loss of selectivity.

Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene dichloride complexes: Applications in ethylene polymerization

The alkenyl substituted zirconocene complexes, [Zr(η5-C5H4{CMeRCH2CH2CH = CMe2})2Cl2] (R = Me (1), Ph (2) were prepared from the reaction of the lithium derivative Li(C5H4{CMeRCH2CH2CH = CMe2}) (R = Me, Ph) with zirconium tetrachloride. The bulky alkyl substituted cyclopentadienyl ligand precursor was prepared as its fulvene derivative (C5H4) = CMeCH2CHMe2 (3) via the reaction of cyclopentadiene with 4-methyl-2-pentanone and then converted to Li(C5H4{CMe2CH2CHMe2}) (4) via nucleophilic attack of LiMe. The reaction of 4 with [TiCl4(THF)2] and ZrCl4 gave the metallocene complexes [M(η5-C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)), respectively. The ansa-ligand precursor, SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7), was prepared via the reaction of 4 with SiMe2(C5HMe4)Cl and subsequently converted to its dilithium derivate, Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8), using n-butyllithium. The ansa-zirconocene complex, [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9), was synthesized by the reaction of 8 with zirconium tetrachloride. Compounds 1–9 were characterized by 1H and 13C{1H} NMR spectroscopy. In addition, the molecular structures of 5, 6 and 9 were determined by single crystal X-ray diffraction studies. The metallocene complexes have been tested as catalyst (with co-catalyst MAO) in the polymerization of ethylene where the substituents on the cyclopentadienyl ligand have a direct influence on the catalytic activity.

Trimerization and tetramerization of ethylene in continuous gas-phase reaction using a Cr-based supported liquid phase catalyst

Selective tri- and tetramerization of ethylene in continuous operation was achieved by immobilization of the homogeneous chromium catalyst plus MAO co-catalyst in a thin film of high boiling hydrocarbons.

Concurrently Improving the Thermal Stability and Activity of Ferrous Precatalysts for the Production of Saturated/Unsaturated Polyethylene

The five unsymmetrical ligands 2-[1-(2,6-dibenzhydryl-4-tert-butylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine (aryl = 2,6-Me2C6H3 (L1), 2,6-Et2C6H3 (L2), 2,6-iPr2C6H3 (L3), 2,4,6-Me3C6H2 (L4), 2,6-Et2-4-MeC6H2 (L5)) and the symmetrical ligand 2,6-bis(1-(2,6-dibenzhydryl-4-tert-butylphenylimino)ethyl)pyridine (L6) have been prepared and characterized by FT IR and 1H/13C NMR spectroscopy and elemental analysis. The treatment of L1–L6 with FeCl2·4H2O afforded the corresponding ferrous chloride complexes (Fe1–Fe6) in excellent yields. A distorted-square-pyramidal geometry with a τ5 value of 0.13 is a feature of the X-ray structure of Fe3; broad paramagnetically shifted peaks are revealed in the 1H NMR spectra for all the iron complexes in solution. On activation with either MAO or MMAO cocatalyst, all iron complexes displayed high activities with modest variations in activities at elevated temperature (up to 12.0 × 106, 12.4 × 106, 12.8 × 106, and 13.1 × 106 g of PE (mol of Fe)−1 h–1 at 50, 60, 70, and ...

Excellent electrically conductive PE/rGO nanocomposites: In situ polymerization using rGO-Supported MAO cocatalysts

Superior electrically conductive PE nanocomposites were prepared with reduced graphene oxide(rGO)-supported MAO cocatalyst via in situ ethylene polymerization. The electrical conductivity of the composites was very high at 1.2 S/m. This value is the highest among reported rGO-filled composites. The cocatalyst system was prepared by modifying with alkoxysilane compound to prevent restacking of the GO plane in the reduction process and solvothermal reduction of GO. The effect of cocatalysts on the properties of nanocomposites and distribution of nanosheets in the polymer matrix was investigated in detail. The mechanical properties and thermal stability of PE/rGO nanocomposites were significantly increased via the addition of a small amount of rGO. These properties resulted from the restacked rGO layers exfoliated in situ by the ethylene insertion between the intercalated layers.

1,3-Dipolar cycloaddition 반응을 통해 기능화된 carbon nanotube 표면 위에 균일계 촉매 담지 및 에틸렌 중합

− In this study, CNT functionalized with pyrrolidine ring via 1,3-dipolar cycloaddition reaction with various amino acid and aldehyde was synthesized. Metallocene was subsequently immobilized on the functionalized CNT and CNT/polyethylene composite was prepared via in-situ ethylene polymerization. The polymerization activities of metallocene supported on CNT functionalized with glycine and benzaldehyde (Gly+BA-CNT) were similar to those of metallocene supported on CNT functionalized with N-benzyloxycarbonylglycine and paraformaldehyde (Z-Gly+PFA-CNT) although its Zr content was lower than that of Z-Gly+PFA-CNT. In the case of metallocene supported on Z-Gly+PFACNT, the even distribution of active sites hindered the diffusion of ethylene monomer and cocatalyst MAO due to steric hindrance during ethylene polymerization. Compared to polyethylene produced from homogeneous metallocene catalysts, CNT/PE composites had a higher initial degradation temperature (T onset ) and maximum mass loss temperature (T max ). It suggests that pyrrolidine functionalized CNT is uniformly dispersed and strongly interacted with the PE matrix, enhancing the thermal stability of PE.

A Novel Polymer Supported Catalyst for Preparation of Sydiopolystyrene

Poly (styrene-co-acrylonitrile) supported TiCl4 was prepared and characterized. IR analysis shows that the absorption of the acronitrile group shifted from 2233cm-1 to 2277cm-1 after its coordination to TiCl4. It is found that this catalyst shows a much higher catalytic activity than that of TiCl4 in the preparation of sydiopolystyrene, especially, it can be used to prepare a styrene rich poly (styrene-co-ethylene), the resulted poly (styrene-co-ethylene) is a crystalline polymer shown a Tm much lower than that of a homo sydiopolystyrene. The molecular simulation result shows that the coordinated metal in the polymer catalyst is more cationic, probably due to an electron withdraw group coordinated to the central metal. This result can help us to understand that the polymer catalyst is more active and there is less cocatalyst MAO was used in the polymerisation process. Based on the results both of the experiment and the molecular simulation, we can give a conclusion that the polymer backbone stabilized the central metal Ti and make it difficulty to be reduced to a TiII complex, and the later shows no activity in the polymerisation. The stabilization is from the coordination of the polymer backbone and not due to an electron donor ligand which is in a normal metallocene.

Synthesis of 4-arms hydroxy-functionalized PMMA-b-PE through combining free radical polymerization with coordination polymerization

The copolymerization of MMA with ethylene was promoted by metallocene complex in the presence of initiator tetra(2,3-epoxy propoxy)silane (Is), reducing agent Zn and cocatalyst MAO, combining free radical polymerization with coordination polymerization via sequential monomer addition strategy in one-pot to produce 4-arms hydroxy-functionalized PMMA-b-PE. The effects of polymerization conditions such as temperature, time, ethylene pressure and Al/Ti molar ratio on the polymerization performance were investigated. 4-Arms hydroxy-functionalized PMMA-b-PE was obtained by solvent extraction and determined by GPC, MALLS, DSC, FT-IR, WAXD and 1H(13C) NMR. The DSC result indicated that the 4-arms hydroxy-functionalized PMMA-b-PE had one Tg at 87.0°C and one Tm at 117.0°C which attributed to Tg of PMMA segment and Tm of PE segment, respectively. The microstructure of 4-arms hydroxy-functionalized PMMA-b-PE was further confirmed by WAXD, FT-IR, and 13C NMR analysis. These results demonstrated that the obtained 4-arms block copolymer consisted of PMMA segment and crystalline PE segment.

Introduction of reactive functionality by the incorporation of divinylbiphenyl in ethylene copolymerization with styrene or 1-hexene using aryloxo-modified half-titanocenes and MAO catalysts

An efficient introduction of vinyl group into poly (ethylene-co-styrene) or poly(ethylene-co−1-hexene) has been achieved by the incorporation of 3,3′-divinylbiphenyl (DVBP) in terpolymerization of ethylene, styrene, or 1-hexene with DVBP using aryloxo-modified half-titanocenes, Cp′TiCl2(O−2,6-iPr2C6H3) [Cp′ = Cp*, tBuC5H4, 1,2,4-Me3C5H2], in the presence of MAO cocatalyst, affording high-molecular-weight polymers with unimodal distributions. Efficient comonomer incorporations have been achieved by these catalysts, and the content of each comonomer could be varied by its initial concentration charged. The postpolymerization of styrene was initiated from the vinyl group remained in the side chain by treatment with n-BuLi. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2581–2587

Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems

The effect of ligand and Al cocatalysts in ethylene polymerization, using V(N-1-adamantyl)Cl2(L) [L = 2-(2,6-Me2C6H3)NCH2(C9H6N), 8-(2,6-Me2C6H3)NCH2(C9H6N)] and V(N-2-MeC6H3)Cl2[2-(2,6-R'2C6H3)NCH2(C5H4N)] (R' = Me, iPr), has been explored. The reaction products in the presence of Et2AlCl or Me2AlCl cocatalyst were polyethylene whereas the reaction product of the 2-methylphenylimido analogues in the presence of MAO cocatalyst was 1-butene with high selectivity, suggesting that the catalyst/cocatalyst nuclearity effect plays a role in this catalysis.

Ethylene copolymerization by half-titanocenes containing imidazolin-2-iminato ligands–MAO catalyst systems

Ethylene copolymerization with 1-hexene, styrene using half-titanocenes containing 1,3-dialkyl- and 1,3-diarylimidazolin-2-iminato ligands, Cp′TiCl2[1,3-R2(CHN)2CN] [Cp′=Cp (1), tBuC5H4 (2); R=tBu (a), 2,6-iPr2C6H3 (b)], have been explored in the presence of MAO cocatalyst. Complex 1a exhibited remarkable catalytic activity for ethylene/1-hexene copolymerization, affording ultrahigh molecular weight copolymers with uniform molecular weight distributions (Mn=1.07–1.31×106, Mw/Mn=1.43–1.82). An opposite trend for effect of N-substituents in 1a,b toward the activity in ethylene and styrene homopolymerization was observed. The ethylene/styrene copolymerizations afforded poly(ethylene-co-styrene)s with uniform compositions and the polymerization by the tBu analogues (1a,2a) proceeded in a living manner with moderate activities, whereas the imidazolidin-2-iminato analogues, CpTiCl2[1,3-R2(CH2N)2CN] (R=tBu, Ph, 2,6-Me2C6H3), afforded a mixture of copolymer and homopolymers or exhibited negligible activity under the same conditions.

Carboranylimine-complexed titanium (IV) organometallics: An investigation of synthesis, structure and catalytic polymerization

The condensation reaction of carboranylmethyl ammonium chloride, 1-(CH2NH3Cl)-1,2-C2B10H11 (1) with phenyl aldehydes produced phenyl(carboranylmethyl)imine ligands, 1-(CH2N = CC6H4R-2)-1,2-C2B10H11 (2 R = H; 3 R = OH). Deprotonation of 2 and 3 with n-BuLi followed by metalation with TiCl4 led to the formation of phenyl(carboranylmethyl)imidotitanium (IV) chlorides, [1-(CH2N = CC6H4R-2)-1,2-C2B10H10]TiCl3 (4 R = H; 5 R = O). Compounds 4 and 5 were found to catalyze the polymerization of ethylene in the presence of co-catalyst MAO to produce high molecular weight polyethylene. In addition, compounds 4 and 5 were also active for copolymerization of ethylene and methyl-10-undecannoate to generate corresponding copolymers.

2-Aldiminophenoxytitanium chloride complexes: Synthesis, characterization, and ethylene (co-)polymerization behavior

A series of trichlorotitanium 2-aldiminophenoxylate complexes (C1–C6) was synthesized by the stoichiometric reaction of TiCl4(THF)2 with the potassium salts of 6-alkyl-2-aldiminophenolates derived from ligands (L1–L6) bearing a bulky benzhydryl substituent, whereas the bis(2-aldiminophenoxy)titanium dichloride (C7) was isolated in the reaction of a ligand L6 with 0.5 equivalents of TiCl4(THF)2. All titanium complexes were characterized by 1H/13C NMR spectroscopy and elemental analysis. Single-crystal X-ray diffraction revealed distorted octahedron geometries around the titanium center for complexes C2, C4 and C7. Upon activation with the co-catalyst MAO, all titanium pre-catalysts exhibited good to high activities (up to 1.3 × 106 g mol (Ti)−1 h−1) for ethylene polymerization at 70 °C, producing polyethylene products with high molecular weights. Furthermore, co-polymerization of ethylene with either α-olefins or norbornene was achieved with activities in the range of 105 g mol (Ti)−1 h−1 by these titanium pre-catalysts along with good incorporation of co-monomer, typically 4.5 mol % for 1-hexene or 13.5 mol % for norbornene, respectively.

Titanium complex bearing 8‐anilino‐1‐naphthalenesulfonate ligand: Synthesis and catalytic behavior toward ethylene (co‐)polymerization

AbstractA novel titanium complex bearing 8‐anilino‐1‐naphthalenesulfonic acid was synthesized. The effects of cocatalyst and reaction conditions on ethylene polymerization were studied. The synthesized titanium complex exhibited high polymerization activity in the presence of MAO cocatalyst. The synthesized titanium complex/MAO catalyst system showed a uniform active site and was very stable at high polymerization temperature. In addition, the copolymerization of ethylene and norbornene was investigated. With the introduction of norbornene, the catalyst activity slightly decreased with MAO as cocatalyst but increased with TEA as cocatalyst. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Crystallization kinetics of PE‐b‐isotacticPMMA diblock copolymer synthesized using SiMe2(Ind)2ZrMe2 and MAO cocatalyst

Polyethylene‐b‐poly(methyl methacrylate) (PE‐b‐PMMA) diblock copolymer has important interfacial applications. Hence, a PE‐b‐isotactic PMMA diblock copolymer was synthesized using SiMe2(Ind)2ZrMe2 and MAO cocatalyst. The polymerization mechanism and the origin of PMMA isotacticity were duly explained. An appropriate nonisothermal Avrami‐Erofeev crystallization model was developed to compare the crystallization kinetics of the above copolymer with that of a PE homopolymer. For both polymers, the model well matched the entire differential scanning calorimeter crystallinity profile, notably for a single Avrami‐Erofeev index, and predicted cylindrical crystal growth. This model particularly overcomes the limitations of the published nonisothermal crystallization models, and provides interesting insight into PE crystallization. The PMMA block significantly decreased the heats of crystallization and fusion, % crystallinity, and the relative crystallization function; increased the nonisothermal crystallization rate constant; and introduced minimal dilution effect whereas the PE block formed a continuous or percolated phase. This study correlates catalyst structure, copolymer block tacticity, and PE nonisothermal crystallization and melting behavior. © 2012 American Institute of Chemical Engineers AIChE J, 59: 200–214, 2013

Thio-Pybox and Thio-Phebox complexes of chromium, iron, cobalt and nickel and their application in ethylene and butadiene polymerisation catalysis

A series of bis(thiazolinyl)- and bis(thiazolyl)pyridine Thio-Pybox ligands and their metal complexes of chromium(III), iron(II), cobalt(II) and nickel(II) has been prepared, as well as a nickel(II) complex containing a monoanionic bis(thiazolinyl)phenyl Thio-Phebox ligand. These new metal complexes have been characterised and used as catalysts, in combination with the co-catalyst MAO, for the polymerisation of ethylene and for the polymerisation of butadiene. In the case of ethylene polymerisation, the Thio-Pybox and Thio-Phebox metal complexes have shown relatively low polymerisation activities, much lower compared to the related bis(imino)pyridine complexes of the same metals. In the polymerisation of butadiene, several Thio-Pybox cobalt(II) complexes show very high activities, significantly higher than the other metal complexes with the same ligand. It is the metal, rather than the ligand, that appears to have the most profound effect on the catalytic activity in butadiene polymerisation, unlike in the polymerisation of ethylene, where bis(imino)pyridine ligands provide highly active catalysts for a range of 1st row transition metals.

Olefin Polymerization by Half-Titanocenes Containing η2-Pyrazolato Ligands−MAO Catalyst Systems

A series of half-titanocenes containing pyrazolato ligands, Cp′TiCl2(3,5-R2C3HN2) (1a−d, 2a−c, 3a−c) [Cp′ = Cp (1), Cp* (2), tert-BuC5H4 (tert-BuCp, 3); R = H (a), Me (b), iPr (c), Ph (d)], have been employed as the catalyst precursors for ethylene polymerization, syndiospecific styrene polymerization, and copolymerization of ethylene with 1-hexene, styrene, and norbornene (NBE) in the presence of MAO cocatalyst. The Cp* analogues, especially 2a,b, exhibited high catalytic activities for ethylene polymerization affording the polymer with unimodal molecular weight distributions, whereas the Cp analogue (especially 1b,c) and the tert-BuCp analogues (3a−c) exhibited high catalytic activities for syndiospecific styrene polymerization. The ethylene/styrene copolymerization using the tert-BuCp−diisopropyl analogue (3c) −MAO catalyst system proceeds in a living manner, irrespective of the styrene concentration employed (in toluene at 25 °C), and the same system exhibited relatively high catalytic activity for the ethylene/NBE copolymerization with highly efficient NBE incorporation.