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  • 1
    Electronic Resource
    Electronic Resource
    Size exclusion behavior of polymers in amide solvents (1995)
    Springer
    Polymer bulletin 34 (1995), S. 585-592 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The abnormal behavior of acrylonitrile polymers shown by size exclusion chromatography (SEC) in N,N-dimethylformamide (DMF) was investigated by using model polymers having variable degrees of sulfonated moieties as electric charged groups. The unexpected small retention volume and very high UV absorption at 280 nm were observed in the case of the samples with ionic sulfonate groups even in very small amounts, as chain ends. The abnormal behavior was confirmed to be due to impurities of DMF decomposition which interact with charged groups in the polymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423355
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  • 2
    Electronic Resource
    Electronic Resource
    Size exclusion behavior of polymers in amide solvents (1995)
    Springer
    Polymer bulletin 34 (1995), S. 593-598 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Size exclusion chromatography (SEC) procedure for the determination of molecular weight and molecular weight distribution of acrylonitrile polymers (PAN) is described. The Mark-Houwink-Sakurada parameters of PAN polymers in DMF and 0.01M LiBr-DMF at 60°C were estimated. The values of a parameters obtained by us for PAN prepared both by persulfate-metabisulfite aqueous system (PAN), and azo-bis-isobutyronitrile in DMF solution (PAN-A) were the same, while for PAN sample containing small amounts of sulfonated pendant groups (PAN-S) was higher. The addition of inorganic salt, such as LiBr, to DMF suppressed the abnormal SEC elution behavior observed in the solvent without the electrolyte although SEC of PAN-A showed almost the same results as in DMF with electrolyte. The universal calibration using monodisperse poly(ethylene oxide) standards as well as application of the Mark-Houwink-Sakurada parameters were satisfactory for the determination of the molecular weights.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423356
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative study on the lamellar crystal structure of high and low density polyethylenes (1997)
    Springer
    Polymer bulletin 38 (1997), S. 707-714 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A comparative study was undertaken on well characterized HDPE and LDPE samples in order to obtain a better understanding of the morphology of the crystalline phase. Thickness of the lamellae was determined by WAXS. The melting points were calculated by empirical and Gibbs-Thomson equations, considering either folded or extended chains, and compared to DSC data. The results confirm that in HDPE the chains are folded, the segment between folds containing about 100 carbon atoms, while in LDPE, the chains are extended, with segments of about 73 carbon atoms in the crystalline core, linked to the paracrystalline layer and amorphous zones, which contain long folds and chain ends, as proposed in the 3-phase model by Vile et al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050109
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  • 4
    Electronic Resource
    Electronic Resource
    Ethylene polymerization with heterogeneous Ziegler-Natta catalysts (1995)
    Springer
    Polymer bulletin 34 (1995), S. 563-567 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary TiCl4/SiO2, Ti(OC4H9)4/SiO2, MgCl2/TiCl4/SiO2 and MgCl2/Ti(OC4H9)4/SiO2 catalysts were prepared by treating silica gel with TiCl4, Ti(OC4H9)4, MgCl2/TiCl4 or MgCl2/Ti(OC4H9)4 in tetrahydrofuran (THF) solution. Ethylene polymerization was performed with these catalysts activated by common alkylaluminum compounds. The influence of magnesium dichloride on catalyst performance was investigated. MgCl2 has enhanced the catalyst activity for both titanium compounds. In addition, all catalyst systems were only active when they were washed with AlCl(C2H5)2 (DEAC).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423352
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  • 5
    Electronic Resource
    Electronic Resource
    Size exclusion behavior of polymers in amide solvents (1996)
    Springer
    Polymer bulletin 36 (1996), S. 729-735 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The size exclusion chromatography of neutral polymers and polymers containing ionic groups was investigated using N,N-dimethylacetamide (DMA) as mobile phase. As reported previously for N,N-dimethylformamide (DMF), acrylonitrile polymers containing charges, even those at terminal end groups, showed markedly small retention volumes and multimodal peaks by refractive index and 280 nm UV detectors. In DMA containing small amounts of LiBr the peaks of the ionic polymers were shifted to small retention volumes while neutral polymers with analogous chemical structures did not show the same behavior. As in the case of DMF the peculiarities observed in DMA were attributed to the formation of supramolecular structures by the interaction of the ionic groups in the polymer and the ionic species from DMA decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338637
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  • 6
    Electronic Resource
    Electronic Resource
    Ethylene polymerization with hafnocene adamantolate/MAO system (2000)
    Springer
    Polymer bulletin 45 (2000), S. 365-372 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new alcoholate of cyclopentadienyl metallocene with voluminous group as ligand substituting chlorine atoms and formula Cp2Hf(OMAd)2 (where Cp = cyclopentadienyl and OMAd = derived of 2-methyl-2-adamantol) was synthesized and employed as catalyst for olefin polymerization. The compound was evaluated in ethylene polymerization activated by methylaluminoxane (MAO) using several experimental conditions. These conditions were determined by a statistic method, and a model for dependent variables like catalyst activity and average molecular weight of polymers were developed. The hafnocene alcoholate produced polyethylenes with molecular weights in the same range of the corresponding metallocene dichloride. The new catalyst system showed high stability under temperature of 100°C. In the presence of H2 as molecular weight controlling agent, the catalyst showed a maximum of activity in the concentration range used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890070009
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  • 7
    Electronic Resource
    Electronic Resource
    Isospecific polymerization of styrene with supported nickel acetylacetonate/methylaluminoxane catalysts (1998)
    Springer
    Polymer bulletin 40 (1998), S. 689-694 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050309
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  • 8
    Electronic Resource
    Electronic Resource
    Large Surface Area Divinylbenzene Copolymers for Size Exclusion Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 63-66 
    Details
    ISSN: 0935-6304
    Keywords: Divinylbenzene copolymers ; exclusion limit ; size exclusion chromatography ; surface area ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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