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  • 1
    Electronic Resource
    Electronic Resource
    Effect of stoichiometry and diffusion on an epoxy/amine reaction mechanism (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 673-689 
    Details
    ISSN: 0887-624X
    Keywords: epoxy/amine mechanism ; crosslinking ; rate law ; diffusion limit ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bulk phase kinetics of an epoxy (DGEBA) /amine (DDS) thermoset have been studied using DSC, FTIR, and 13C-NMR. In the absence of catalyst, the reaction was found to involve a main exothermic reaction between epoxide and amine hydrogen and a side reaction between tertiary amine formed in the main reaction and epoxide. The main reaction was exothermic while the side reaction had no discernable exotherm. Etherification did not occur to any significant extent. Since only the main reaction is exothermic, DSC was very useful for studying the main reaction kinetics. FTIR was used for determining whether epoxide and amine hydrogen were consumed at different rates as a way of following the side reaction. An IR band previously unused by other investigators was used to monitor the amine hydrogen concentration. NMR confirmed the above mechanism by identifying the formation of a quaternary ammonium ion/alkoxide ion pair as a reaction product of tertiary amine and epoxide. This mechanism has been successfully fit to a rate law valid over the entire extent of reaction. The rate constant for the epoxy/amine addition reaction was found to depend on hydroxide concentration (extent), reaction temperature, and glass transition temperature and included contributions from uncatalyzed and autocatalyzed parts. The side reaction (quaternary ammonium ion formation) formed weak bonds which did not affect the overall system Tg. Both reactions were second order. The rate constants for the main reaction first increase with increasing extent due to autocatalysis by hydroxide before decreasing due to the diffusion limit caused by gelation and vitrification. © 1995 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330409
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    [N-Alkyl-(2-pyridyl)methanimine]copper(I) Complexes: Characterisation and Application as Catalysts for Atom-Transfer Polymerisation (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1799-1806 
    Details
    ISSN: 1434-1948
    Keywords: Atom-transfer polymerisation ; Methyl methacrylate ; Copper(I) ; Schiff base ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterisation of a series of novel bis(imine)copper(I) complexes and their use in atom-transfer polymerisation of methyl methacrylate is described. Several N-alkyl-(2-pyridyl)methanimines (alkyl = n-butyl, isobutyl, sec-butyl, n-propyl) and N-(n-propyl)-1-(2-pyridyl)ethanimine as ligands have been fully characterised. Three bis[N-alkyl-(2-pyridyl)methanimine]copper(I) complexes, [Cu{(C5H4N)CH=N(iBu)}2][BF4], [Cu{(C5H4N)C(CH3)=N(nPr)}2][PF6], and [Cu{(C5H4N)CH=N(sBu)}2][BF4] have been structurally characterised; all having a distorted tetrahedral arrangement of co-ordinating nitrogen atoms surrounding the metal centre. All of the catalysts were found to be effective atom-transfer polymerisation catalysts for the polymerisation of MMA in hydrocarbon solution. However, it was discovered that the performance of the catalysts containing n-alkyl substituents was superior to those containing branched alkyl substituents. The presence of branching in the alkyl substituent results in a reduction of reaction rate and a corresponding broadening of the polydispersity index.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Polymerisation of methyl methacrylate with tert-butyllithium and triisobutylaluminium in toluene: mechanism of initiation and termination by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI TOF MS) (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 725-732 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerisation of methyl methacrylate (MMA) using triisobutylaluminium/tert-butyllithium in hydrocarbon at 0°C and -78°C has been investigated by matrixassisted laser desorption ionisation time-of-flight mass spectrometry (MALDI TOF MS). Although the system gives extremely good control over molecular weight and narrow molecular weight distribution, initiation of polymerization can be complicated by formation of small amounts of tert-butyl isoprenyl ketone (1), and termination of polymerization can occur by end cyclisation of the end unit of 3. Both complications in initiation and termination can be avoided by suitable reaction conditions. Incorporation of 1 is suppressed by increasing the alkylaluminium content and by higher temperature. Termination by cyclisation has been found to occur over much longer time scales than propagation and can therefore be avoided by controlled termination after the appropriate reaction time.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030161004
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of methacrylic multi-arm star copolymers by “arm-first” group transfer polymerisation (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 871-881 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Methacrylic star polymers were synthesized by the “arm-first” method of star polymer formation by the addition of difunctional monomer, ethylene glycol dimethacrylate, to living linear poly(methyl methacrylate) as prepared by group transfer polymerisation (GTP). The effects of living polymer concentration and ratio of difunctional monomer to living polymer are discussed, and show how macromolecular design and control may be imposed on the number of arms and molecular weight of the star polymer. Diluting the difunctional crosslinking monomer with monomer has been examined with the view to establishing funtionalisation of the star core.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980317
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