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  • 1
    Electronic Resource
    Electronic Resource
    Dual functional catalysis for ethylene polymerization to branched polyethylene. I. Evaluation of catalytic systems (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3027-3042 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of low-density polyethylene, that is, a density of less than 0.925 g/cm3, has traditionally been accomplished by the use of free-radical initiators at high ethylene pressures or of an alpha olefin comonomer such as 1-butene at lower pressures. We investigated an alternative route to branched, low-density polyethylene with a single monomer, ethylene, as the feed in conjunction with multicomponent catalyst systems capable of in situ dimerization of ethylene and subsequent copolymerization to produce low-density polyethylene. This article discusses the details of the evaluation of a number of dual-functional systems based on Ziegler-Natta catalysts. Specific, well defined, dual-functional catalyst systems which could easily produce branched, low-density polyethylene with levels of 20-30 branches per 1000 carbon atoms were developed. Variations in the relative number of component catalysts resulted in systematic, predictable changes in the properties of the polyethylene produced, which demonstrated the utility of the dual-functional catalyst concept.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170221125
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  • 2
    Electronic Resource
    Electronic Resource
    Dual-functional catalysis for ethylene polymerization to branched polyethylene. II. Kinetics of ethylene polymerization with a mixed homogeneous-heterogeneous Ziegler-Natta catalyst system (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 1069-1084 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The previous paper in this series described several catalytic systems which can be used for simultaneous ethylene dimerization to 1-butene and copolymerization of the in situ-formed olefin with ethylene to form branched polyethylene. Such catalytic systems allow the synthesis of linear low-density polyethylene from a single monomer source. This article presents a more detailed description of one of the dual-functional catalyst systems studied, a mixed homogeneous-heterogeneous Ziegler-Natta catalyst, Al(C2H2)3-Ti(Oi-C3H7)4-TiCl4/MgCl2/polyethylene, at 90°C. Discussed are kinetics of ethylene dimerization with the soluble component, Al(C2H5)3-Ti(Oi-C3H7)4, and the effects of aluminum alkoxides on the system. Addition of the ethylene dimerization catalyst to the solid component, Al(C2H5)3-TiCl4/MgCl2/polyethylene, results in a partial decrease in polymerization activity. Some of the decrease can be attributed to the presence of 1-butene in the reaction medium. Measurement of the reactivity ratio kEE/kEB for two catalytic systems, the solid component and the title dual-functional catalyst, demonstrated that the presence of the dimerization component results in a twofold increase in the reactivity ratio, from 20 to ca. 40.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240601
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  • 3
    Electronic Resource
    Electronic Resource
    Oligomerization of ethylene with a homogeneous sulfonated nickel ylide-aluminum alkoxide catalyst (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 147-155 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various organoaluminum compounds strongly affect reactivity of a sulfonated nickel ylide complex in its reactions with ethylene. The complex, if used alone, is an active single-component catalyst for ethylene oligomerization to linear 1-alkenes. Al(C2H5)3 and tetraethylaluminoxane completely deactivate the catalyst by reducing it to Ni(O). Alkylaluminum halides, such as Al(C2H5)2Cl and Al(C2H5)Cl2, convert the nickel complex into a very active catalyst for ethylene dimerization to mixtures of butenes. Aluminum alkoxides, e.g., Al(C2H5)2OC2H5, AlC2H5(OC2H5)2, and Al(OC2H5)3, significantly increase oligomerization activity by a factor of 20-100. The distribution of 1-alkenes (in the C4—C40 + range) produced with the sulfonated nickel ylide-aluminum alkoxide catalyst follows the Flory molecular weight distribution law. The ratio of the chain termination to chain propagation rate constants is ca. 0.3 and is not temperature-sensitive in the 50-120°C range. Kinetic analysis of the ethylene oligomerization reaction with the binary catalytic system showed that the number of active centers is proportional to the nickel complex concentration. The effective activation energy of ethylene oligomerization with the catalyst is ca. 27 kJ/mol. The oligomerization catalysts loose their activity in time. The activity decay follows the first-order kinetic law. The rate of the decay increases with increasing temperature and is caused mainly by the intrinsic instability of active species.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270113
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  • 4
    Electronic Resource
    Electronic Resource
    An analysis of circular intensity differential scattering measurements: Studies on the sperm cell of eledone cirrhosa (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2043-2064 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study represents the first systematic attempt to characterize the possible sources of artifacts that can interfere with the measurement of circular intensity differential scattering (CIDS) as a function of the scattering angle. A theoretical analysis of the effect of imperfect incident circular polarizations in the measurement of baselines from nonchiral scatterers and in the signals from chiral samples is derived. From this analysis the requirements of the tolerance on the quality of the incident circular polarizations to unequivocally measure the CIDS effect are established. The protocol for alignment of the CIDS instrument and the characterization of the incident polarizations utilized in these studies are described in detail. CIDS measurements on suspensions of helical sperm cells are presented. The experimental results are modeled computationally with the use of the current CIDS theory. Good agreement between the data and the computations is obtained. The results clearly indicate the ability of CIDS to provide information on the long-range chiral organization of samples in solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251103
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    Paper (German National Licenses)
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