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  • 1
    Digitale Medien
    Digitale Medien
    Influence of water on ethylene polymerization catalyzed by titanocene systems (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2553-2558 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1978.021791021
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  • 2
    Digitale Medien
    Digitale Medien
    Comparison of methods for determination of the number of active centers in Ziegler-Natta polymerizationsDedicated to Professor Ing. Dr. O. Wichterle on the occasion of his 70th birthday (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 1975-1985 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Four intrinsically different methods for the determination of the number of active centers were employed in propylene polymerization catalyzed by the typical heterogeneous system TiCl3/AlEt2Cl: (i) determination of M̄n (GPC method) and calculation of number of macromolecules therefrom; (ii) quenching with BuOT and determination of tritium in the polymer; (iii) quenching with CO or CO2 and determination of carbonyl groups in the polymer (IR spectroscopy); (iv) quenching with SO2 and determination of sulfur in the polymer. The first two methods exhibited a reasonable agreement for the number of active centers. Method (iii) gave much lower values, whereas method (iv) was found to be virtually unsuitable due to a high extent of side reactions of SO2 with the polymer. A similar comparison of the methods was made in ethylene polymerization catalyzed by the typical homogeneous systems Cp2TiEtCl/AlEtCl2 and Cp2TiEtCl/alumoxane. Method (ii) gave a much lower number of active centers than method (i), due perhaps to a low extent of alcoholysis of the Ti—C bond or to a high kinetic isotope effect. CO2 appeared to be entirely inert as a quenching agent and CO had been reported to show side reactions. It follows that none of the above quenching methods have universal application and thus literature data should be considered with caution.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1983.021841003
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  • 3
    Digitale Medien
    Digitale Medien
    Determination of the number of active centers in Ziegler-Natta polymerization of propene using sulfur-containing stoppers, 3.Part 2: cf.2. Carbon disulfide tagging - Its mechanism and applicability (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1519-1528 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This paper analyses in detail the dependence of the number of CS2 tags in polypropene (PP) on the relative polymerization rate upon addition of CS2. It is shown that centers of higher activity are subjected to a faster deactivation and tagging by CS2. It was deduced that their higher reactivity with CS2 is not likely to be connected with their stereospecificity. Irreversibility of the CS2-insertion reaction was documented, at least under the conditions of our experimentation. A mechanism of action of CS2 was outlined and adsorption coefficients were determined for the TiCl3/AlEt2Cl and TiCl3/AlEt3 systems. A direct proof of insertion of CS2 into the growing transition metal-carbon bond could not be obtained. An indirect method (employing COS as a poison) allowed us to conclude that in case of CS2 two atoms of sulfur are incorporated into the polymer per each deactivated center. On this basis, the number of centers was determined for both catalyst systems. A much higher propagation rate constant (kp) was found for the AlEt3-cocatalyzed polymerization. It was concluded that the above method is applicable to the determination of active centers, but caution must be exerted in widening its application to other systems.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1990.021910705
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  • 4
    Digitale Medien
    Digitale Medien
    Determination of active centers in heterogeneous Ziegler-Natta catalytic systems using carbon oxides (1977)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 261-266 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1977.021780127
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  • 5
    Digitale Medien
    Digitale Medien
    Polymerization of ethylene catalyzed by titanocene systems, 1. Catalytic systems Cp2TiEtCl/AlEtCl2 and Cp2TiEtCl/(AlEtCl2 + H2O) (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 2549-2561 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The kinetics of the ethylene polymerization catalyzed by the Cp2TiEtCl/AlEtCl2 system in toluene were investigated. Hydrolysis of AlEtCl2 in benzene was studied and the resulting oxyaluminium compounds were used as cocatalysts together with Cp2TiEtCl as catalyst for ethylene polymerization. A strong enhancement of the cocatalytic activity for the formation of oxyaluminium compounds was observed, accompanied by an increase of molecular weight. The catalyst efficiencies were found to be rather high in both the Cp2TiEtCl/AlEtCl2 and the Cp2TiEtCl/(AlEtCl2 + H2O) system. Transfer reactions are suppressed under the applied experimental conditions, but termination reactions, leading to non-stationary kinetic patterns, may be assumed for both systems.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1980.021811212
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  • 6
    Digitale Medien
    Digitale Medien
    Adsorption of propylene and allene on TiCl3·1/3 AlCl3 and polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1773-1779 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Adsorption of propylene and allene from the gas phase on TiCl3·1/3 AlCl3 and TiCl3·1/3 AlCl3/AlEt2Cl catalyst was measured volumetrically. In the ranges of 296-334 K and 1-100 kPa, the adsorbed amounts of both gases was found to be approximately proportional to the gas pressure. The adsorbed amount of allene is about twice as high as that of propylene under the same conditions. Low heats of adsorption of both propylene and allene support the assumption of the physical nature of the adsorption. Addition of AlEt2Cl to the TiCl3·1/3 AlCl3 catalyst did not change substantially the sorption properties of the catalyst. Polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl in heptane was found to be first order in monomer and the rate decreases with increasing yield. A mechanism of retardation by the polymer formed is probably operative. Both heptane-soluble and heptane-insoluble polyallenes are produced. The soluble polymer has M̄n ≈ 103 and a very narrow molecular weight distribution (M̄w/M̄n = 1,2 ± 0,2). Polyallene comprises mainly vinylidene units.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1987.021880801
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  • 7
    Digitale Medien
    Digitale Medien
    Determination of the number of active centers in Ziegler-Natta polymerization of propene using sulfur-containing terminating agents, 1. Application of carbon disulfide (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1489-1499 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polymerization of propene catalyzed with TiCl3 · 1/3(AlCl3)/AlEt2Cl or TiCl3 · 1/3(AlCl3)/AlEt3 systems in heptane at 323,2 K in the presence of CS2 was studied. It was demonstrated that the sharp decrease of rate, observed upon addition of CS2, is not due to a decrease of the organometal concentration, although some consumption of the organometal was evidenced by means of IR measurement. Tagging of the growing chains was monitored by determination of the sulfur content in the polymer. Side reactions of CS2, leading to a blank content of sulfur in polypropylene, were observed in the presence of catalytical components even after their deactivation. Thus, a thorough washing of the polymer was necessary. A substantial increase of heptane solubles observed upon addition of larger amounts of CS2 was found to be due to a much lower molecular weight of the polymer, while stereospecificity of the catalytical system was virtually preserved. It was concluded that CS2 behaves as a suitable terminating and tagging agent.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1989.021900629
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  • 8
    Digitale Medien
    Digitale Medien
    Determination of the number of active centers in Ziegler-Natta polymerization of propene using sulfur-containing terminating agents 2.Part 1: cf.1. Tagging of growing chains during retardation of polymerization by carbon disulfide (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 589-601 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The CS2-induced retardation of propene polymerization catalyzed by TiCl3/AiEt2Cl and TiCl3/AlEt3 systems was investigated. From the two systems, the latter was much more active in polymerization and also exceedingly more susceptible to retardation by CS2. At least for the TiCl3/AlEt2Cl-catalyzed polymerization, there is no diffusion limitation imposed on the reaction of growing chain with CS2. It was found that the number of sulfur tags introduced by the above CS2 treatment is dominantly related to the ratio of polymerization rates before and after CS2 addition. Monomer plays a dual role during the CS2 treatment: on one hand it enhances the CS2 insertion into the growing metal-polymer bond, on the other hand it competes with CS2 in the same reaction. CS2 reacts preferentially with centers of highest reactivity. It allows, in principle, the determination of the reactivity distribution of active centers. Several potential side reactions which might lead to an increase of the number of tags in polymer were considered. None of the side reactions play an important role except for a reaction of CS2 with chains formed via transfer with the organometal compound in AlEt3-cocatalyzed polymerization.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1990.021910314
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  • 9
    Digitale Medien
    Digitale Medien
    Polymerization of ethylene catalyzed by titanocene systems, 2.Part 1: cf.2. Catalytic systems Cp2 TiRCl/oxyaluminium compounds (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 1127-1134 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Ethylene polymerization, catalyzed by Cp2TiEtCl or Cp2TiMeCl and cocatalyzed by oxyaluminium compounds, formed via hydrolysis of AlEtCl2, AtEt2Cl, AlEt3, AlMeCl2, AlMe2Cl, AlMe3, and AlEt(OBu)Cl, was studied. The cocatalytic activity of oxyaluminium compounds was found to decrease with increasing number of alkyl substituents in the corresponding alanes. The only inactive cocatalyst from the oxyaluminium compounds studied is the one formed via hydrolysis of AlEt(OBu)Cl. Oxyaluminium compounds from methylalanes are substantially less active than those from ethylalanes. If the same aloxane cocatalyst is employed, the catalytic activities of both Cp2TiEtCl and Cp2TiMeCl are similar. The molecular weight distributions of polyethylene are narrow for the systems Cp2TiRCl/(oxyaluminium compounds from AlEtCl2); fairly broader distributions were found for systems Cp2TiRCl/(oxyaluminium compounds from AlMeCl2). Systems with oxyaluminium compounds from dialkyl- or trialkylalanes yield polyethylene with distinctly bimodal distribution curves. The mechanism of ethylene polymerization catalyzed by titanocene systems cocatalyzed by oxyaluminium compounds is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1981.021820413
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  • 10
    Digitale Medien
    Digitale Medien
    Retardation of the TiCl3·1/3 AlCl3/AlEt2Cl catalyzed propylene polymerization by allene and its relevance to the determination of the number of active centers (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1781-1794 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The retardation of the TiCl3/AlEt2Cl catalyzed propylene polymerization by allene was studied. On the basis of the results, a mechanism of the competitive chemisorption on active centers was proposed. A non-linear dependence of the polymerization rate on the amount of allene consumed can be described in terms of the existence of two types of active centers, their numbers being 2 and 20 mmol·mol-1Ti, respectively, differing very substantially in the adsorption coefficients. Copolymerization of propylene with allene was investigated, using the above catalytic system. Assuming identical active centers, the following copolymerization parameters were obtained: r1 = 0,66 ± 0,66 and r2 = 40 ± 30. Based on these results, the consumption of allene by copolymerization during the retardation of propylene polymerization was described in quantitative terms.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1987.021880802
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