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  • Chemistry  (5)
  • 1995-1999  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 2.Part 1: cf. ref.6 Kinetic investigations with methyl methacrylate in toluene (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 399-406 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the polymerization of methyl methacrylate initiated by lithium alkyls (tert-butyllithium or ethyl α-lithiobutyrate) was investigated in the presence of aluminium alkyls (triethylaluminium or triisobutylaluminium) in toluene at -78°C. The rate of polymerization decreases considerably once the living dimer is formed. This suggests that the aluminate end-group coordinates with the penultimate ester group of the polymer chain, thus decreasing reactivity. The results are at variance with an activated monomer mechanism.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030160601
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Mean square radius of gyration and hydrodynamic radius of jointed star (dumbbell) and H-comb polymers (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 759-769 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Equations for the mean square radius of gyration and the hydrodynamic radius for jointed stars (dumbbells) and H-combs are derived, based on random flight statistics for each subchain. Comparision with literature data on computer simulations and experimental data for H-combs show good agreement for the g-value of the mean square radius of gyration even in good solvents. This suggests that for the mean square radius of gyration the relative dimension of a H-comb relative to the linear molecule of the same degree of polymerization is not altered significantly by long range interactions, as in the case of star polymers. For the hydrodynamic radius the situation is different. Fair agreement is found when comparing our results with viscosity measurements under θ conditions, while in good solvents the viscosity of the branched molecule is more reduced than predicted by our results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1996.040050409
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of linear and three-arm star tert-chlorine-telechelic polyisobutylenes by a two-step conventional laboratory process (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 417-425 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A two-step conventional laboratory process was developed for the synthesis of mono- and difunctional linear and three-arm star tert-chlorine-telechelic polyisobutylenes (PIB) with desired molecular weights (MW) and narrow molecular weight distribution (MWD) by living carbocationic polymerization (LCCP). This polymerization method applies easy to handle operations and chemicals. LCCP of isobutylene (IB), was carried out in CH2Cl2 as solvent and with BCl3 as coinitiator in the first step to obtain soluble low MW PIB prepolymer with narrow MWD. This was followed by addition of hexane, TiCl4 and additional monomer in the second step to prepare PIBs with desired MW and narrow MWD in practically any suitable MW region. Comparison of the one-step and two-step processes is also described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180509
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  • 4
    Electronic Resource
    Electronic Resource
    Hyperbranched methacrylates by self-condensing group transfer polymerization (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 865-873 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of hyperbranched methacrylates was achieved by self-condensing group transfer polymerization of 2-(2-methyl-1-triethylsiloxy-1-propenyloxy)ethyl methacrylate (1). “Back-biting” is shown to be the predominant side reaction. In spite of this, the compact nature of the hyperbranched molecules was demonstrated through SEC-viscosity measurements and comparison with a linear analogue. The degree of branching can be controlled by copolymerization with conventional monomers, e.g. MMA, and the living polymers can be used as macroinitiators for star-shaped polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180915
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of reaction conditions on the chain end structure and functionality during dehydrochlorination of tert-chlorinetelechelic polyisobutylene by potassium tert-butoxide (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 661-663 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dehydrochlorination of tert-chlorine-telechelic polyisobutylene with potassium tert-butoxide in refluxing tetrahydrofuran is quantitative after 22 h, but results in ca. 3% endo olefin chain ends which are not reactive in some subsequent functionalization reactions. The formation of these undesired structures is most likely due to simultaneous thermally induced HCl loss. Lower temperatures and longer reaction times led to exclusive formation of external double bonds in some cases but to incomplete dehydrochlorination.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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