The polymerization of hexene-1, octene-1 and decene-1 with a modified Ziegler catalyst based on the product of interaction of TiCl4, Et2AlCl, and n-Bu2O in toluene has been studied. Et2AlCl, i-Bu2AlCl, and a combination of Et2AlCl with MgBu2 were used as cocatalysts. The addition of a small amount of MgBu2 to Et2AlCl resulted in a sharp increase in the catalytic system activity along with decreases in the molecular masses of the formed polymers. It has been shown that a change of [Mg]/[Al] ratio makes it possible to produce polyolefins in a wide range of molecular masses with high effectiveness. The above mentioned polymers are amorphous ultrahigh molecular materials with predominantly isotactic structure.

Effect of cocatalysts on the performance of three post-metallocene catalysts based on complexes I–III in Scheme 1 is studied by comparing their activity in the presence of two cocatalysts, MAO and a combination of AlEt2Cl and MgBu2, in propylene polymerization reactions. The second cocatalyst produces significantly more active catalysts. Analysis of GPC, DSC and 13C NMR data for the polymers suggests that the activity increase is caused by the formation of new types of active centers. Some of the new centers are isospecific and operate according to the enantiomorphic stereocontrol mechanism.

The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl2 · MgCl2 and [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra-(perfluorophenyl-1,3-dioxolane-4,5-dimethanol]TiCl2· (LiCl)2 are studied. The first catalyst shows higher activity in both reactions and forms a lower molecular mass PP. This PP is characterized by a wide molecular-mass distribution that can be described by a set of five or six Flory components with different average molecular masses. Along with heterogeneity with respect to kinetic parameters, there is heterogeneity with respect to stereospecificity. Some of the sites form a high-molecular-mass highly isotactic polymer whose melting point is ≥150°C, whereas other sites produce syndiotactic and atactic PPs. For the most isospecific sites, a stereocontrol mechanism similar to the mechanism typical for metallocene catalysts with C 1-symmetry is advanced. The catalysts under study are composed of the [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl2 complex supported on LiCl and MgCl2, respectively.

The structural characteristics of polypropylene samples prepared with two post-metallocene catalysts based on complexes bis-{M-(3,5-di-tert-butyl-salicylidene)-4-[bis-(5-methyl-2-furyl)methyl]aniline}titanium dichloride and [(4R,5R)-2,2-dimethyl-alpha,alpha,alpha',alpha'-tetra(pentafluorophenyl)-1,3-dioxalan-4,4-dimethanol)titanium dichloride are investigated by GPC, C-13 NMR, IR, DSC, and XRD methods. A combination of the first complex and MAO forms a single-center catalyst which polymerizes propylene to a nearly perfectly atactic polymer. A combination of the second complex and MAO forms a multicenter catalyst system producing polymer mixtures with broad molecular weight distributions containing five to six Flory components with different average molecular weights. Relative contents of the Flory components strongly depend on the type of solvent in the polymerization reactions. Some of the active centers produce high molecular weight, highly isotactic crystalline material with the melting point over 154 degrees C. The nature of steric errors in these polymer fractions (determined by C-13 NMR) can be explained by a variant of stereocontrol similar to that exerted by metallocene catalysts of the C-1 symmetry. (C) 2009 Elsevier Ltd. All rights reserved.

Исследована полимеризация пропилена, этилена и сополимеризация этих олефинов на постметаллоценовых катализаторах [(4R,5R)-2,2-диметил- ’, -тетра(перфторфенил)-1,3-диоксолан-4,5-диметанол]титан(IV) дихлорид и бис-{N-(3,5-ди-трет-бутилсалицилиден)-4-[бис-(5-метил-2-фурил)метил]анилин}титан(IV) дихлорид. Полимеризация пропилена и его сополимеризация с этиленом проведены в среде жидкого мономера, а полимеризация этилена – в толуоле при постоянной концентрации мономера. В качестве сокатализатора использован полиметилалюмоксан. Активность катализаторов в полимеризации пропилена и этилена при 50°С равна 10 и 45 кг ПП/моль Ti ч моль С3Н6/л, 178.5 и 2700 кг ПЭ/моль Ti ч моль С2Н4/л соответственно. Показано, что при сополимеризации пропилена с этиленом активные центры обоих катализаторов избирательно полимеризуют этилен. Полученные сополимеры имеют блочное строение (r1r2 = 4.6), в результате чего в их структуре формируется кристаллическая фаза полиэтилена. Полипропилен и сополимеры пропилена с этиленом являются эластомерными материалами. Образцы полипропилена, синтезированные на [(4R,5R)-2,2-диметил- ’, -тетра-(перфторфенил)-1,3-диоксолан-4,5-диметанол]титан(IV) дихлориде, наряду с хорошими эластичными свойствами имеют высокую температуру плавления 150–157°C. Полиэтилен представляет собой линейный полимер со степенью кристалличности 37–45% и температурой плавления 133–134°C. Изучены механические свойства полимеров и сополимеров.

The polymerization of propylene and ethylene and the copolymerization of these olefins with postmetallocene catalysts [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol] titanium(IV) dichloride and bis{ N -(3,5-di tert -butylsalicylidene)-4-[bis(5-methyl-2-furyl)methyl]aniline}titanium( IV) dichloride have been studied. The polymerization of propylene and its copolymerization with ethylene have been carried out in a liquid monomer, while the polymerization of ethylene has been performed in toluene at the constant concentration of the monomer. Polymethylaluminoxane has been used as a cocatalyst. The activity of the catalysts in the polymerization of propylene and ethylene at 50°C is ∼ 10 and ∼45 kg PP/mol Ti h mol C 3 H 6 /l and 178.5 and 2700 kg PE/mol Ti h mol C 2 H 4 /l, respectively. It has been established that, in the copolymerization of propylene with ethylene, the active sites of both catalysts selectively polymerize ethylene. The resulting copolymers have a block structure ( r 1 r 2 = 4.6); as a result, the crystalline phase of polyethylene is formed in them. Polypropylene and propylene-ethylene copolymers are elastomeric materials. Polypropylene samples synthesized with [(4R,5R)-2,2-dimethyl-α,α,α′,α′-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]titanium(IV) dichloride demonstrate a high melting point (150–157°C) in combination with good elastic properties. Polyethylene is a linear polymer with the degree of crystallinity varying from 37 to 45% and a melting point of 133–134°C. The mechanical properties of the polymers and copolymers have been investigated.

The polymerization and copolymerization of vinylcyclohexane with α-olefins in the presence of several heterogeneous and homogeneous catalytic systems were studied. It was shown that, with respect to activity in the polymerization of vinylcyclohexane, the tested catalysts can be arranged in the following order: α-TiCl3 < titanium-magnesium catalyst < metallocene catalyst. Poly(vinylcyclohexane) prepared with heterogeneous catalytic systems is a solid semicrystalline polymer. The properties of polymers synthesized with homogeneous systems differ substantially depending on the type of the metallocene used. In the presence of metallocenes with a C2 symmetry, crystalline powderlike products arise, while in the case of metallocenes with C1 and C s symmetries, polymerization yields amorphous viscous products. Molecular-mass distributions of poly(vinylcyclohexane) samples prepared using both heterogeneous titanium-magnesium catalysts and homogeneous metallocene complexes show a bimodal pattern, indicating the heterogeneity of active centers of these catalysts. Upon introduction of a comonomer (ethylene, propylene, and 1-hexene) into the reaction mixture, the activity of all studied catalytic systems increases. When Me2C(3-Me-Cp)(Flu)ZrCl2 and rac-Me2SiInd2ZrCl2 are used as catalysts, the degree of crystallinity of the copolymers grows owing to the presence of ethylene or propylene units in poly(vinylcyclohexane) chains.

The effect of a direct current discharge on the films of polypropylene and copolymers of propylene and hexene-1 synthesized with an isospecific catalytic system, rac-Me2SiInd2ZrCl2–polymethylaluminoxane, was investigated. The treatment of isotactic polypropylene films by the discharge did not affect the ratio of crystalline phases in the polymer to a measurable extent. However, for the plasma treated films of copolymers of propylene and hexene-1 (the hexene-1 content of 1–2mol%), a structural transformation of γ-modification into α-modification has been noticed. The observed phase transition has no apparent relation to any changes in microstructure of the copolymer chain because melting temperature values and the stereoregularity parameters of the samples remained practically unchanged. An experimental investigation of the specific influence exerted by individual components of a direct current discharge on the crystalline structure of copolymers has been undertaken. The exposure to a quantum component of the discharge did not induce any changes in the phase composition of the irradiated samples. The heating of the samples led to a negligible change of their phase composition. It has been determined that the surface of polypropylene and propylene/hexene-1 copolymer films facing the cathode in the course of the direct current discharge treatment had an accumulated negative charge Q>10nC/cm2 which persisted for a long time afterwards. It has been suggested that the electrical field of a negative discharge may be the main cause of the γ-into α-phase transition in propylene/hexene-1 copolymers under the plasma effect. To verify this assumption, a propylene/hexene-1 copolymer film was charged under electron beam with energy of 4keV. The electron beam treatment of the film resulted to the negative charge value of 11nC/cm2. The electron beam irradiation has induced the phase transition which was quite similar to the transition observed as the result of plasma treatment. So, it may be concluded that the phase transition from crystal γ-modification to α-modification under the effect of direct current discharge which has been investigated for copolymers of propylene and hexene-1 is induced by electric field of the negative charge accumulated at the surface layers of the films of the copolymers.

The copolymerization of propylene and 1-hexene initiated by isospecific catalytic systems containin ansa-metallocene complexes with a C-2 symmetry, rac-Me2Si(Ind)(2)ZrCl2 and rac-Me2Si(4-Ph-2-Me-Ind)(2)ZrCl2), and a syndiospecific catalytic system based on a C-s symmetric complex Ph2C(Cp)(Flu)ZrCl2 was studied. Polymethylaluminoxane or a mixture of polymethylaluminoxane and Al-i-Bu-3 was used as a cocatalyst. The addition of small amounts of 1-hexene to the reaction mixture brings about activation of isospecific catalytic systems. The activity of 1-hexene in copolymerization varies in the sequence: rac-Me-2 Si(Ind)(2)ZrCl2 < rac-Me2Si(4-Ph-2-Me-Ind)(2)ZrCl2 < Ph2C(CP)(Flu)ZrCl2. It was shown that the resulting copolymers are characterized by a monomer unit distribution close to random (r(1)r(2) = 0.7-1.9). An optimum Al-i-Bu-3 : Zr ratio ensuring a marked reduction in the consumption of poly methylaluminoxane with a concomitant increase in the copolymer yield was determined. It was shown that the incorporation of even small amounts of 1-hexene (0.9-12.0 mol %) into PP chains leads to a decrease in its melting temperature and degree of crystallinity and causes an appreciable rise in the elasticity and impact strength of the final polymers.

The polymerization of 3-methyl-1-butene with heterogeneous titanium-magnesium and homogeneous metallocene catalysts that differ in symmetry type, such as Me2C(3-Me-Cp)(Flu)ZrCl2 (C-1 symmetry) and Ph2C(Cp)(Flu)ZrCl2 (CS symmetry), was studied. The activity of metallocene catalysts is much higher than that of titanium-magnesium systems under comparable conditions. Poly(3-methyl-1-butene) prepared using titanium-magnesium catalysts and Me2C(3-Me-Cp)(Flu)ZrCl2 is an isotactic polymer with a degree of crystallinity of 28.5-54%. A polymer synthesized in the presence of Ph2C(Cp)(Flu)ZrCl2 is virtually amorphous. It was shown that the regularity of poly(3-methyl-1-butene) chains depends on the type of metallocene catalyst used.

The activity and stereospecificity of the catalytic system TiCl4-Et2AlCl of propylene polymerization was studied in relation to the nature of carbon-containing supports like graphite, fullerene C-60, anthracene, polyacetylene, and fullerene soot. Graphite and fullerene soot were most effective supports. Isotactic polypropylene was formed at a high rate at definite (transition metal)/support ratios. The active centers of graphite and fullerene soot tt ere shown to be different, the catalytic activity being higher in graphite.

Studies of activity and stereospecificity in polymerizations of propylene and butene-1 with several metal-complex catalysts fixed on a graphite surface are reported. High catalytic activity was observed at a strictly determined Ti: graphite ratio. Maximum stereospecificity is observed at the maximum of catalytic activity. Characterization of the catalyst obtained from the interaction of TiCl4(C2H5)2AlCl with graphite by Chromatographic, polarographic, X-ray and ESR techniques was directed to the origin of the modifying effect of graphite. These results indicated the formation of stable metal complexes containing Ti compounds with TiC2H5 moieties in the sites of crystal-lattice defects. Some electrophysical and mechanical properties of polypropylene-graphite sample are also presented.

Electrophysical and physicomechanical properties of polymerizationally filled composites containing natural or synthetic graphite were compared with those of composites prepared by blending. A more uniform distribution of graphite particles in polymerizationally filled composites resulted in a linear dependence of resistance on sample length; this was not the case with the blended composites. Temperature coefficients of resistance of composites were measured at 4.2 - 423 K. Contrary to blended composites, polymerizationally filled composites sustained multiple temperature jumps from 4.2 K to ambient temperature. Significant difference in mechanical properties of polymerizationally filled and blended composites was explained by different polymer-to-graphite adhesion. Polymetizationally filled composites displayed higher electric and heat conductivities than the blended composites of the same composition.