Search results for "polymerization"

Effect of silica-type sol–gel carrier’s structure and morphology on a supported Ziegler–Natta catalyst for ethylene polymerization

2006

Abstract Silica xerogels with different structures and morphology, synthesized using a sol–gel procedure, were used as a carrier of vanadium catalysts (VOCl 3 /AlEt 2 Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated.

Constrained formation of 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridines and their cobalt(ii) chloride complexes: synthesis, chara…

2015

A series of 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridine derivatives (L1-L5) was synthesized, and individually reacted with cobalt(II) chloride to form the corresponding cobalt chloride complexes (C1-C4). These compounds were characterized, and the single crystal X-ray diffraction for two representative cobalt complexes was carried out. The molecular structures indicate that 2,7-bis(arylimino)cyclopentapyridines act as tridentate ligands; however, one of the Co-N coordinative bonds is weak due to the spatial separation of nitrogen atoms. Upon activation with either MAO or MMAO, all cobalt complexes exhibit catalytic activities toward ethylene. Polymerization takes place…

Tritylpyridinium tetrakis(pentafluorophenyl)borate as an efficient activator for “constrained-geometry” catalysts in ethylene polymerization

2004

Abstract Ethylene polymerization with linked amido-cyclopentadienyl or “constrained-geometry” titanium catalysts, Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 N t Bu)X 2 (X=Me, Bz, Cl), activated by tritylpyridinium tetrakis(entafluorophenyl)borate, [Ph 3 C(NC 5 H 5 )] [B(C 6 F 5 ) 4 ], and silica-supported tritylpyridinium tetrakis(entafluorophenyl)borate (PySTB) was found to proceed with high activity. 1 H NMR spectra in CD 2 Cl 2 suggest that ([Ti(η 5 :η 1 -C 5 Me 4 ,SiMe 2 N t Bu)Me (NC 5 H 5 )] + is formed as the main cationic species. Using the heterogeneous cocatalyst PySTB in hexane, unexpectedly high ethylene polymerization activity was achieved, giving high molecular weight polyethylenes with exc…

Non-bridged amido cyclopentadienyl complexes of titanium: synthesis, characterization, and olefin polymerization catalysis

2000

Alkylation of Ti(η 5 -C 5 Me 5 )(NMe 2 )Cl 2 gives thermally stable, crystalline dialkyl complexes Ti(η 5 -C 5 Me 5 )(NMe 2 )R 2 (R=Me, CH 2 Ph, Ph). The molecular structure of the dibenzyl complex reveals an unprecedented conformation of the doubly bonded NMe 2 group which is turned parallel to the η 5 -C 5 Me 5 ligand, according to single-crystal X-ray diffraction studies. Treatment of the dibenzyl complex with B(C 6 F 5 ) 3 in d 5 -bromobenzene solution results in the quantitative formation of a thermally (>10°C) unstable monobenzyl cation as solvent-separated ion pair [Ti(η 5 -C 5 Me 5 )(NMe 2 )CH 2 Ph] + [PhCH 2 B(C 6 F 5 ) 3 ] − which efficiently polymerizes styrene syndiospecifically…

Dialkyl titanium complexes that contain a sulfur-linked bis(phenolato) ligand:

2002

Abstract The sulfur-linked bis(phenol) 2,2′-thiobis(2-tert-butyl-4-methylphenol), tbmpH2, reacted cleanly with titanium tetrachloride to give the orange titanium dichloro complex [Ti(tbmp)Cl2]2 in virtually quantitative yield. Reaction of the dichloro complex [Ti(tbmp)Cl2]2 with methyllithium at low temperature gave the unexpectedly thermally robust, yellow dimethyl complex [Ti(tbmp)Me2]. The reaction of the dichloro complex with benzyl Grignard reagent in pentane afforded the highly crystalline dibenzyl complex [Ti(tbmp)(CH2Ph)2] as a 1,4-dioxane adduct. The single crystal X-ray crystallography revealed a centrosymmetric 1,4-dioxane-bridged molecule that contains two fragments containing s…

Copolymerization of ethylene with norbornene or 1-octene using supported ionic liquid systems

2016

Copolymerization of ethylene with norbornene (E/NB) and ethylene with 1-octene (E/Oct) is performed using supported ionic liquid (SIL) systems, in which metallocene (Cp2VCl2) or post-metallocene [VCl2(salenCl2)] vanadium catalysts are immobilized in pyridinium chloroaluminate ionic liquid supported on silica. The studied SIL catalysts show higher activities as well as stability than their non-supported analogues. In addition, higher activities and better comonomer incorporation are observed for norbornene (above 30 mol%). The comonomer incorporation has considerable influence on copolymer molecular weight (M w), melting temperature, crystallinity degree, and microstructure of the copolymers…

The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler–Natta catalysts supported on MgCl2(THF)2

2000

Abstract The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with α-olefin over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated by Et2AlCl was studied. The results show that the introduction of a longer α-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of α-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer i…

Structural analysis of linear/branched ethylene block copolymers

2017

Synthesis and structural characterization of ethylene copolymers containing double-decker silsesquioxane as pendant groups and cross-linkage sites by…

2018

Abstract The copolymers of ethylene with the double-decker silsesquioxane (DDSQ) were synthesized by copolymerization with the use of metallocene and bis(phenoxy-imine) catalysts. The influence of the kind of the catalyst and polyreaction conditions on the performance of copolymerization as well as on the properties of the copolymers was studied. Depending on polyreaction parameters, the DDSQ contents in the copolymer varied in the range of 0.93–11.53 wt% which determined the compositions and the structural properties of copolymers. DDSQ incorporated into the polymer chain could constitute pendant groups in the main chain or it could act as a cross-linking agent. The ethylene/DDSQ copolymer…

Titanium complexes having chelating diaryloxo ligands bridged by tellurium and their catalytic behavior in the polymerization of ethylene

2000

A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-R-6-R‘-C6H2O)2}]2 (5b, X = Cl, R = Me, R‘ = tBu; 6a, X = OiPr, R = R‘ = H; 6b, X = OiPr, R = Me, R‘ = tBu), were prepared. 5b and 6b were determined by X-ray crystallography to have chloro- and isopropoxo-bridged dimeric structures. The structural data for these complexes indicated that the Ti−Te coordination bonds were stronger than the similar Ti−S coordination bonds in the corresponding sulfur-bridged complexes. The reaction of (C5R5)TiCl3 (R = H, Me) with 2,2‘-Te(4-R-6-R‘-C6H2OLi)2 gave monocyclopentadienyl derivatives, (C5R5)TiCl{2,2‘-Te(4-Me-6-tBu-C6H2O)2} (7, R = H; 8, R = Me). The…