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  • 1
    Electronic Resource
    Electronic Resource
    Microgel formation in emulsion copolymerization. I. Polymerization without seed latex (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1403-1413 
    Details
    ISSN: 0887-6266
    Keywords: microgels ; emulsion polymers ; molecular weight distribution ; crosslinking ; Monte Carlo method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microgel formation during emulsion copolymerization of methyl methacrylate and ethylene glycol dimethacrylate is investigated both experimentally and theoretically. It was found that the average crosslinking density is fairly high even from a very early stage of polymerization. The molecular weight distribution (MWD) development in emulsion crosslinking copolymerization is completely different from that in homogeneous polymerization. Because the maximum molecular weights allowed to exist is limited by the particle size, a comprehensive model for the MWD development in nonlinear emulsion polymerization must account for the size of polymerization locus properly. During the formation of microgels, a drastic change in the weight-average molecular weights, which is characteristic of gelation in homogeneous media, is not always required. In a typical microgel formation process where a large mole fraction of divinyl monomer is used, the average molecular weights may increase just linearly with conversion in which a sharp MWD shifts to higher molecular weights with the progress of polymerization. It is shown that the microgels formed in emulsion polymerization are characterized as intramolecularly crosslinked macromolecules that occupy a very large weight fraction in each polymer particle. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Polyradical distribution in free radical crosslinking of polymer chains (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2099-2104 
    Details
    ISSN: 0887-6266
    Keywords: molecular weight distribution ; polyradical ; gel ; polymer modification ; nonlinear polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    General matrix formula for the weight-average molecular weights of crosslinked polymer systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2423-2433 
    Details
    ISSN: 0887-6266
    Keywords: gelation theory ; nonlinear polymerization ; nonrandom crosslinking ; molecular weight distribution ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On the basis of the first-order Markovian statistics, we propose a general matrix formula for the weight-average molecular weight of crosslinked polymer systems, explicitly given by M̄w = M̄w,0 + WX0 (I - X)-1 Sf. This equation is valid for both step and chain-growth polymerizations, including those in a nonequilibrium state irrespective of the reactor types used. In the context of the present theory, the onset of gelation is simply stated as a point at which the largest eigenvalue of the matrix X reaches unity (i.e., det(I - X) = 0). The present theory provides a unified point of view for various types of gelling systems. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2423-2433, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Markovian approach to nonlinear polymer formation: Free-radical polymerization with chain transfer to polymer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 357-371 
    Details
    ISSN: 0887-6266
    Keywords: gelation theory ; nonlinear polymerization ; molecular weight distribution ; branched polymers ; polymer modification ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A Markovian model is proposed for nonrandom branching reactions, by using free-radical polymerization that involves chain transfer to polymer as an example. Free-radical polymerizations are kinetically controlled; therefore, each primary polymer molecule experiences different history of branched structure formation. By assuming that the primary chains with the identical birth time conform to the same chain connection probabilities, the nonlinear structural development can be viewed as a system in which the primary chains formed at different birth times are combined into nonlinear polymers in accordance with the first-order Markov chain statistics. An explicit formula for the weight-average chain length is derived in a matrix form. The onset of gelation is simply stated as a point at which the largest eigenvalue of the transition matrix X reaches unity, i.e., det(X - I) = 0. This criterion for the onset of gelation can be considered as an extension of the Flory/Stockmayer theory to a nonequilibrium reaction system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 357-371, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Microgel formation in emulsion copolymerization: II. Seeded polymerization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1415-1422 
    Details
    ISSN: 0887-6266
    Keywords: microgels ; gelation ; emulsion polymers ; seeded polymerization ; molecular weight distribution ; crosslinking ; Monte Carlo method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microgel formation in seeded emulsion copolymerization of methyl methacrylate and ethylene glycol dimethacrylate is investigated both experimentally and theoretically. By introducing seed latex, the network structure development can be changed significantly. Even when the crosslinking density development takes a similar pattern as the crosslinking copolymerization in homogeneous media, the molecular weight development shows both types of behavior that is characteristic of emulsion polymerization without seed latex and of homogeneous polymerization, depending on the primary polymer chain length and the mole fraction of the divinyl monomer used. Once the microgels are formed, the weight-average molecular weight increases just linearly with conversion due to a very small locus of polymerization. The present investigation reveals important characteristics of gelation phenomena in a limited space. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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