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  • 1
    Digitale Medien
    Digitale Medien
    Superactive and stereospecific catalysts. IV. Influence of structure of esters on MgCl2 supported olefin polymerization catalystsPart III of this series: J. C. W. Chien and Y. Hu, J. Polym. Sci. Polym. Chem. Ed., in press. (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 273-284 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: CH-type catalysts were prepared by reacting MgCl2 · ROH, where ROH is 2-ethyl hexanol (EH), (R)-2-octanol (R-20), and (S)-2-octanol (S-20), with TiCl4 in the presence of di-i-butyl phthalate (BP), di-i-butyl terephthalate (BT), (-)-dimenthyl phthalate (MP), or (-)-dimenthyl terephthalate (MT). The MT catalysts were found to incorporate 8.9 to 13% Ti whereas the BP catalysts contain only 1.9 to 2.6% Ti. Comparison of the CH(EH, BP) and CH(EH, MT) catalysts showed that they have about equal number of isospecific active sites per gram of catalyst and the same rate constants of propagation for their nonspecific sites, however, the isospecific sites in the latter are less active by comparison. Consequently, the CH(EH, BP) catalysts is five times more active than the CH(EH, MT) catalysts and produces polypropylene which is 97% isotactic (reflux n-heptane insoluble) as compared to 84.7% for the latter. The catalysts derived from 2-octanols are much less active than the corresponding catalysts prepared with 2-ethyl hexanol due to lack of reactivity with phthalic anhydride which permits excessive incorporation of TiCl4 to form nonstereospecific catalytic sites as well as inactive Ti species.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1990.080280204
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of polarity of the medium on the stereospecific polymerization of propylene by ansa-zirconocene catalyst (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2049-2056 
    Details
    ISSN: 0887-624X
    Schlagwort(e): metallocenes ; olefin polymerizations ; Ziegler-Natta catalysts ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Propylene was polymerized with rac-ethylene-bis (1-η5-indenyl)dichlorozirconium/methylaluminoxane in solvents of different polarity. The poly (propylene) formed was separated by solvent extraction; 13C-NMR and DSC measurements were made on the polymer fractions. The poly(propylene) in each solvent fraction has its characteristic molecular weight steric pentad distributions, melting transition temperature, and enthalpy for fusion irrespective of the polymerization medium. The results suggest that the medium dielectric constant does not affect the polymerization rate or the intrinsic stereoselectivity, propagation and chain transfer rates a given catalytic species but can alter the occurrence of steric insertion errors through shifting of distributions of the propagating species producing poly(propylenes) of different stereoregularities. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1994.080321106
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  • 3
    Digitale Medien
    Digitale Medien
    Solid-State NMR characterization of a superactive supported ziegler-natta catalystThis is Part XXXI of the series on MgCl2-supported Ziegler-Natta catalyst. Part XXX was: J. Vizzini, F. Ciardelli, and J. C. W. Chien, “Stereoselective Polymerization of α-Olefins by Heterogeneous Chiral Ziegler-Natta Catalysts,” Macromolecules, 25, 3199 (1992). (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 2173-2179 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The formation of CH-type catalysts has been investigated by high-resolution and solid-state NMR. These catalysts are prepared from a soluble MgCl2 and 2-ethyl-1-hexanol adduct (MgCl2·3EH) by reaction with phthalic anhydride (PA) to form dioctylphthalate (DOP) and then with TiCl4 in the presence of di-i-butylphthalate (BP). In the model systems MgCl2·3EH/PA, MgCl2/BP, and MgCl2/TiCl4/BP, the ester is complexed with MgCl2 and /or TiCl4 in two or more states. Only single-ester C=O and OCH2 resonances are seen in TiCl4/BP, probably due to exchange of ester coordinations. CH-catalysts prepared by three different procedures exhibit a single mode of bonding for the ester. The chemical shift values are consistent for ester complexed with MgCl2. The most active and stereoselective catalyst has the most shielded chemical shift values for the C=O and  - OCH2 -  carbons, shortest TH1 and TH1p, and longest TCH relaxation times. These parameters change monotonically with the decrease of activity and stereoselectivity of the catalyst preparation. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1993.070481211
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  • 4
    Digitale Medien
    Digitale Medien
    Difference in stereoselective polymerization of 4-methyl-1-hexene by homogeneous and heterogeneous Ziegler-Natta catalysts (1992)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 13 (1992), S. 479-484 
    Details
    ISSN: 0173-2803
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/marc.1992.030131101
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  • 5
    Digitale Medien
    Digitale Medien
    Dynamics of a cascade of two continuous stirred tank polymerization reactors with a binary initiator mixture (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 333-352 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The dynamic behavior of two continuous stirred tank reactors in series has been investigated for free radical solution polymerization of styrene with a binary mixture of two initiators having different thermal decomposition activities. For a wide range of initiator feed composition, both reactors exhibit quite complex nonlinear steady state and transient behavior. When the reactor residence time is used as a bifurcation parameter, the second reactor can have up to five steady states. For certain range of reactor operating conditions, bifurcations to various types of periodic solutions have been observed, such as Hopf bifurcation, isolas, period doubling, period-doubling cascade, and homoclinics. The effects of other reactor variables, such as total initiator concentration, coolant temperature, and reactor volume ratio on the reactor dynamics, are illustrated to show the complex dynamic behavior of the two-reactor system catalyzed by a mixture of t-butyl perbenzoate and benzoyl peroxide.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760310506
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  • 6
    Digitale Medien
    Digitale Medien
    Dynamics of a continuous stirred tank reactor for styrene polymerization initiated by a binary initiator mixture. II: Effect of viscosity dependent heat transfer coefficient (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 494-505 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The dynamic behavior of the solution polymerization of styrene in a continuous stirred tank reactor is analyzed with a mixture of tert-butyl perbenzoate and benzoyl peroxide as an initiator system. In the modeling of the reactor, a viscosity dependent reactor wall heat transfer coefficient is used to account for the changing heat transfer efficiency as monomer conversion and polymer molecular weight increase. The steady state and bifurcation behaviors have been investigated with the reactor residence time, initiator feed composition, initiator concentration, feed solvent volume fraction, and coolant temperature as bifurcation parameters. Unlike the reactors with constant heat transfer coefficient, the present system exhibits relatively simple steady state and dynamic bifurcation behaviors. Oscillatory behavior is observed only when the solvent volume fraction in the feed exceeds 0.2. The dynamic simulation of the reactor also indicates that a feedback temperature controller may fail to maintain the reactor temperature when the heat transfer coefficient changes as a result of process disturbances.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760320707
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  • 7
    Digitale Medien
    Digitale Medien
    High mileage catalysts for olefin polymerization, 34Part 33: cf. 1. Methanolysis of titanium, vanadium and chromium olefin polymerization catalysts (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1639-1643 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: 14CH3O3H was used to quench ethylene polymerization by transition metal catalysts. 3H labeling occurred exclusively for Ti-containing catalysts, whereas more than 95% of the chains were labeled with 14CH3 for the Cr-containing catalysts. Both modes of labeling occurred with V-containing catalysts. The observed phenomena indicate a change of “coordinate-carbanionic” to “coordinate-carbocationic” character for the alkyls of Ti, V and Cr in this order.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940611
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  • 8
    Digitale Medien
    Digitale Medien
    Regio- and stereo-selective alternating copolymerization of carbon monoxide with propene (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2579-2603 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Compounds of palladium with ten different chelated bisphosphine ligands were investigated for their catalysis of alternating copolymerization of propene with carbon monoxide. The bisphosphine structure and chelate ring size influence strongly the activity, regio- and stereo-selectivity of the catalysts. Molecular mechanics calculations on the π-olefin complex showed that the non-bonded interaction between propene and the ligands on Pd is both regio- and stereo-selective. Primary insertion is about seven times more probable than secondary insertion for the Pd complex of bis(diphenylphosphino)butane ligand. The enantioselective catalysts favor the meso enchainment of propene. Gas chromatography/mass spectrometry (GC-MS) of oligomers showed that most chains are initiated by Pd—H species with less frequent initiation by Pd—OCH3 complexes; β-hydrogen elimination is the dominant chain termination process.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1993.021940915
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  • 9
    Digitale Medien
    Digitale Medien
    The flocculation of kaolin suspensions with anionic polyacrylamides of varying molar mass and anionic character, 2Part 1: cf.20.. Polarographic study of the adsorption of anionic polyacrylamides onto clay (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1067-1074 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A selective method using polarography was developed for the determination of the degree of adsorption of anionic polyacrylamides onto Kaolinite. Four polymers of the same anionic character but different molar mass were studied. Limiting adsorption of the polyacrylamides onto the clay increased with their molar mass.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1990.021910509
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  • 10
    Digitale Medien
    Digitale Medien
    An investigation into the nature of the electrochemical and surface properties of polyacrylamides and a study of their adsorption onto the surface of papermaking woodpulps using alternating-current polarography (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2875-2893 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A cationic polyacrylamide was examined using polarography, constant potential coulometry, photon correlation spectroscopy, electrocapillarity and potentiometric titrimetry. A polarographic response was found in differential-pulse polarography (DPP), direct-current and Kalousek modes at -1,7 V versus a silver/silver chloride electrode. In each case the magnitude of the response was a function of polymer concentration. However, it is thought that the response is not due to the polymer itself but impurities found with it. These were found to have a pK of 4,75. The polymer appears to develop a more open structure in LiCl solution (〈0,0013 mol/L). The unwashed polymer was found to greatly increase the interfacial tension at the mercury drop, but this effect was considerably reduced on washing the polymer in 70% acetone solution. Hydrolysis of the polymer seems to occur at pH 10. The suppression of the negative tensammetric peak of poly(ethylene glycol) (PEG200) by a range of cationic polyacrylamides was used for their analysis in the determination of their adsorption onto the surface of woodpulp. The adsorption was found to be a function of both their cationicity and mean molar mass. The rate of hemicellulose desorption from the woodpulp appears to be pH dependent. The impurity is thought to be mainly adipamic acidSystematic name: 5-carbamoylpentanoic acid..
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1991.021921204
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