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  • 1985-1989  (62)
  • 1960-1964  (10)
  • Polymer and Materials Science  (55)
  • Life and Medical Sciences  (17)
  • 11
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high-mileage catalysts for olefin polymerization. X. Effect of hydrogen and catalytic site deactivation (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 2707-2727 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of H2 on propylene polymerization initiated by a MgCl2/EB/PC/AlEt3/TiCl4-3 AlEt3/MPT catalyst was studied. Hydrogen increases significantly the initial rate during the early stage of the polymerization to give a higher yield of polymer than reactions without H2. But H2 reduces the yield toward the latter stages so that the net effect on the total yield can be quite small. There is no appreciable effect of H2 on either the isotacticity index or polydispersity of the products. It decreases molecular weight proportional to (pH2)1/2. The chain transfer by H2 resulted in a decrease of total metal polymer bond concentration with time of polymerization. The rate constants of hydrogen chain transfer for the two kinds of isospecific and nonspecific sites are \documentclass{article}\pagestyle{empty}\begin{document}$ k_{tr1^{\rm i}}^{\rm H} $\end{document} = 5.1 × 10-3, \documentclass{article}\pagestyle{empty}\begin{document}$ k_{tr2^{\rm i}}^{\rm H} $\end{document} = 2.7 × 10-3, \documentclass{article}\pagestyle{empty}\begin{document}$ k_{tr2^{\rm a}}^{\rm H} $\end{document} = 7.5 × 10-3, \documentclass{article}\pagestyle{empty}\begin{document}$ k_{tr2^{\rm a}}^{\rm H} $\end{document} = 4.4 × 10-3, in units of torr1/2 sec-1 at 50°. Hydrogen assists in the deactivation of the catalytic sites as does propylene; rates of the former and the latter vary with (pH2)1/2 and [C3H6]1/2, respectively, with ktH = (12.1 ± 0.9) M-1 torr-1/2 sec-1 and ktM = (65.3 ± 3.3) M-3/2 sec-1 at 50° and A/T = 167. The mechanism for deactivation of catalytic sites are discussed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080241101
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  • 12
    Electronic Resource
    Electronic Resource
    Phenyl thiazyl compounds: Synthesis and electrical conductivity (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1433-1443 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of substituted phenylene-dithio-bis(phenyldithiazyl) (PDBPD) and phenylthiophenyldithiazyl (PTPD) compounds have been synthesized utilizing the facile reaction between N-trimethyl silylimides and aromatic sulfenyl chlorides. The compounds are insulators with conductivities of 10-8-10-12 (Ω cm)-1. However, they can be oxidized with Br2 to conductivities of 10-3-10-5 (Ω cm)-1 for pressed pellets. Electron donating and withdrawing substituents on the phenyl ring markedly alter the electrical transport properties. While PTPD compounds are soluble in many solvents, the PDBPD derivatives are only sparingly soluble.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250519
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  • 13
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high-mileage catalysts for olefin polymerizations. XVIII. Effect of hydrogen and lewis bases (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2881-2892 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen has been found earlier to increase the initial rate of polymerization by MgCl2/EB/PC/AlEt3/TiCl4-AlEt3/MPT, CW-catalyst (+Bi, +Be) (EB, ethyl benzoate; PC, p-cresol; MPT, methyl-p-toluate), but decays more rapidly as compared to polymerizations in the absence of H2. In this study the effect of H2 was studied when either the internal Lewis base, EB Bi, or the external Lewis base, MPT Be, or both are deleted from the CW-catalyst. H2 does not affect the stereospecificity of all the catalysts, but causes a slight increase of polymer yield, whereas the yield is virtually unchanged by H2 for the catalysts activated with Be. Unlike the catalyst (+Bi, +Be) where H2 increases active site concentrations [Ti*] about threefold, it affects [Ti*] negligibly when Be is absent. The rate constants of propagation is about the same with or without H2 for the CW-catalyst (+Bi, -Be) or (-Bi, -Be); the same statement can be said about the rate constant of chain transfer with AlEt3 or with H2. Hydrogen increases the rate of catalyst site deactivation for the various catalysts in the order of(+Bi, +Be) 〉 (-Bi, -Be) 〉 (+Bi, -Be).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251022
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  • 14
    Electronic Resource
    Electronic Resource
    A mechanistic study of polyimide formation from diester-diacids (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2175-2183 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous work by a number of researchers has noted the presence of anhydride during the imidization step of polyimide polymer processing from diester-diacids and diamines. This has been often, and incorrectly, dismissed as being due to the reversion of the intermediate amide-acid. Comparison of the relative rates of reactions among model compounds demonstrates the intermediacy of anhydride in the imidization reaction. When creation of the anhydride is blocked, the production of amide-acid is greatly slowed. Infrared and NMR observations of mixtures of monomers confirm the production of anhydride as a necessary intermediate in the imidization reaction occuring during the production of polyimide polymers from diester diacids.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250814
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  • 15
    Electronic Resource
    Electronic Resource
    Metallocene-methylaluminoxane catalysts for olefin polymerization. I. Trimethylaluminum as coactivator (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 3089-3102 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethylene was polymerized by Cp2ZrCl2-methylaluminoxane (MAO) catalysts where a portion of the MAO was replaced with trimethyl aluminum (TMA). At a total Al to Zr ratio of 1070, there is neither appreciable loss of productivity nor change in polymerization profile for TMA/MAO ≤ 10. The productivity is reduced only by two- to three-fold for TMA/MAO ≤ 100 accompanied by a 10 min induction period. Aging of this catalyst did not affect the induction period, but improves its productivity. The kinetic isotope effect for radiolabeling with tritiated methanol is 2.0. About 40% of the Zr is active for the catalyst with {99 [TMA] + 1[MAO]} to Zr ratio of 100. The rate constants for propagation and chain transfer were obtained. The mechanisms for the mixed TMA and MAO cocatalyst system are discussed. The results of this work have important practical significance. MAO is a hazardous material to synthesize and only in low yields. The replacement of 〉 90% of MAO with TMA represents a substantial saving since as much as 0.1M of the former is commonly used for a polymerization.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080261117
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  • 16
    Electronic Resource
    Electronic Resource
    Superactive and stereospecific catalysts. II. Kinetics of propylene polymerizations (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 2973-2989 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of propylene polymerization by superactive CH-catalyst prepared from toluene solution of MgCl2 · EH/PA/TiCl4-TEA/PES was investigated. The results are compared with CW-catalyst prepared from crystalline MgCl2/EB/PC/TEA/TiCl4-TEA/MPT (abbreviations given in the text). The former is four times more active than the latter and produces more isotactic polypropylene. The CH-catalyst has 25% of the Ti as isospecific sites as compared to 6.7% for the CW-catalysts. These sites have the same rate constant of propagation so that the higher polymerization activity of the CH-catalyst is attributable simply to a greater number of active sites. Differences in the kinetics of deactivation and of chain transfer for the two catalysts are described.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080261109
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  • 17
    Electronic Resource
    Electronic Resource
    Magnesium chloride-supported high-mileage catalysts for olefin polymerization XI. Determinations of poly(decene-1) molecular weight chain dimension and thermal transitions (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 2217-2230 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decene-1 was polymerized with the CW catalyst and fractionated by precipitation technique. Light-scattering and viscometric measurements on these fractions established the relationship [η] = 5.19 × 10-3 Mw0.77. The unperturbed mean square end-to-end distance is (〈Ro2〉/M)1/2 = (6.17 ± 0.34) × 10-9. Light-scattering data is consistent with a relatively stiff molecule with length of L = 1.75 × 10-5 cm for poly(decene-1) with MW = 397,000. Its mean square radius of gyration 〈Rg2〉 is 2.79 × 10-11 cm.2 The ratio of L2/〈Rg2〉 = 11 is close to the theoretical ratio of 12 for this kind of macromolecule.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240916
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  • 18
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high mileage catalysts for olefin (decene-l) polymerization XIV. Propagation and chain transfer (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 919-934 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decene-l was polymerized with the MgCl2/ethylebenzoate/p-cresol/AIEt3/TiCl4-AlEt3/methyl-p-toluate catalyst at 50° using an A/T ratio of 167 and a range of monomer concentration. The concentration of the two kinds of active sites are [Ti1*] = 12% and [Ti2*] = 4% of the total titanium. The rate constants of propagation are 24 M-1 s-1. Chain transfers to AIEt3, monomer, and by β-hydride elimination have rate constant values of 1.7 × 10-3 M-1 s-1, 1.34 × 10-2 M-1 s-1, and 1.7 × 10-2 s-1, respectively. Poly(decene-l) have relatively narrow MW which are unchanged during the course of a polymerization. Therefore, the active site concentrations in the CW catalyst for propylene and decene polymerization are identical and their rate constant values agree within a factor of 2. However, the rate of decene polymerization depends on fractional order of monomer concentration and decreases with the increase of activator concentration. Furthermore, the formation of metal polymer bonds has a rate independent of these concentrations. These kinetic behaviors are a manifestation of absorption processes of these species which are not seen in propylene polymerizations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250316
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  • 19
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high mileage catalysts for olefin (decene-1) polymerization XV. Termination and energetics (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1011-1026 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerizations of decene-1 were carried out from 0° to 70° at A/T = 167 and [M] = 0.75 M initiated by 0.17, 0.34, and 0.69 mM of Ti contained in the MgCl2/ethylbenzoate/p-cresol/AlEt3/TiCl4-AlEt3/methyl-p-toluate catalyst. The rate of polymerization is directly proportional to the catalyst concentration. About 12% of the Ti in the catalyst is initially active at 50°; they are 1.4%, 8.8%, and 9.4% at 0°, 25°, and 70°, respectively. The changes of Rp with temperature parallels the variations in the active site concentration. The decline of Rp with time has second-order plots with slopes which are inversely proportional to the catalyst concentration, but the rate constants for these deactivations are nearly the same for decene and propylene polymerizations. These results strongly support a mechanism of deactivation involving two adjacent sites in the catalyst particle surfaces. The rate constants of propagation and of chain transfer to AlEt3, the energetics for these processes, and MW and MW distribution data have been obtained.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250407
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  • 20
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high-mileage catalysts for olefin polymerization. XVII. Effect of lewis base on propylene polymerization (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2847-2870 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A systematic study has been made on the functions of external Lewis base (Be, methyl-p-toluate, MPT) and internal Lewis base (Bi, ethyl benzoate, EB) for the CW-catalyst system MgCI2/EB/PC/AlEt3/TiCl4-AlEt3/MPT (PC, p-cresol). Bi is a nonstereoselective modifier. It increases the active site concentrations and rate constants of propagation, kp, of both the isospecific and nonspecific sites, and thus the productivities of the stereoregular and irregular polypropylenes by five- to tenfold. It seems that Bi complexes with the MgCl2 support to lower the electronegativity of the surface Mg atoms. It also acts to lower the rate constant of chain transfer to aluminum alkyl, kAtr, by two- to fourfold. The action of Be is highly stereospecific. The isotacticity index of polypropylene is ≫ 95% in the presence of Be but ≪ 68% without it. Addition of Be decreases nonspecific [Ti*]a by about (11 ± 2)-fold; there is only about a twofold reduction of the isospecific [Ti*]i. It decreases kp,a about three times but has no effect on kp,i, so that the latter is (21 ± 4) times the former. Be decreases kAtr,i for transfer with aluminum alkyl much more than it does to kAtr,a; but it does not affect the rates of chain transfer with monomer and by β-hydride elimination or the rate of catalyst deactivation. The number of active sites without Be is [Ti*]i = 15% and [Ti*]a = 55% for a total of 70%. In the presence of Be they are both about 6%. Optimum performance in propylene polymerizations requires both Bi and Be in the case of the CW-catalyst.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251020
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