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Robert M. Waymouth – One of the best experts on this subject based on the ideXlab platform.

  • Zwitterionic Ring-Opening Polymerization: Models for Kinetics of Cyclic Poly(caprolactone) Synthesis
    Macromolecules, 2014
    Co-Authors: Hayley A. Brown, Silei Xiong, Grigori A. Medvedev, Young A. Chang, M. Abu-omar, James M. Caruthers, Robert M. Waymouth

    Abstract:

    Investigations of the kinetics of zwitterionic ring-opening polymerization of e-caprolactone by N-heterocyclic carbenes (NHC) were carried out to illuminate the key reaction steps responsible for the formation of high molecular weight cyclic poly(caprolactones). Modeling of both the decay in Monomer concentration as well as the evolution of molecular weights and polydispersities were necessary to identify the key reaction steps responsible for initiation, propagation, cyclization and chain-transfer. Nucleophilic attack of the NHC on e-caprolactone to generate reactive zwitterions is slow and reversible. The modeling indicates that less than 60% of the carbenes are transformed to active zwitterions, but that these zwitterions rapidly Add Monomer and cyclize by intramolecular backbiting of the terminal alkoxides on internal esters of the zwitterions. This cyclization event maintains the concentration of active zwitterions. The reactivation of cyclized chains by active zwitterions is a key step that leads to…

  • Zwitterionic Ring-Opening Polymerization: Models for
    Kinetics of Cyclic Poly(caprolactone) Synthesis
    , 2014
    Co-Authors: Hayley
    A. Brown, Silei Xiong, Young A. Chang, M. Abu-omar, James M. Caruthers, Grigori
    A. Medvedev, Robert M. Waymouth

    Abstract:

    Investigations of the kinetics of
    zwitterionic ring-opening polymerization
    of ε-caprolactone by N-heterocyclic carbenes (NHC) were carried
    out to illuminate the key reaction steps responsible for the formation
    of high molecular weight cyclic poly­(caprolactones). Modeling of both
    the decay in Monomer concentration as well as the evolution of molecular
    weights and polydispersities were necessary to identify the key reaction
    steps responsible for initiation, propagation, cyclization and chain-transfer.
    Nucleophilic attack of the NHC on ε-caprolactone to generate
    reactive zwitterions is slow and reversible. The modeling indicates
    that less than 60% of the carbenes are transformed to active zwitterions,
    but that these zwitterions rapidly Add Monomer and cyclize by intramolecular
    backbiting of the terminal alkoxides on internal esters of the zwitterions.
    This cyclization event maintains the concentration of active zwitterions.
    The reactivation of cyclized chains by active zwitterions is a key
    step that leads to high molecular weight poly­(caprolactones)

Hayley A. Brown – One of the best experts on this subject based on the ideXlab platform.

  • Zwitterionic Ring-Opening Polymerization: Models for Kinetics of Cyclic Poly(caprolactone) Synthesis
    Macromolecules, 2014
    Co-Authors: Hayley A. Brown, Silei Xiong, Grigori A. Medvedev, Young A. Chang, M. Abu-omar, James M. Caruthers, Robert M. Waymouth

    Abstract:

    Investigations of the kinetics of zwitterionic ring-opening polymerization of e-caprolactone by N-heterocyclic carbenes (NHC) were carried out to illuminate the key reaction steps responsible for the formation of high molecular weight cyclic poly(caprolactones). Modeling of both the decay in Monomer concentration as well as the evolution of molecular weights and polydispersities were necessary to identify the key reaction steps responsible for initiation, propagation, cyclization and chain-transfer. Nucleophilic attack of the NHC on e-caprolactone to generate reactive zwitterions is slow and reversible. The modeling indicates that less than 60% of the carbenes are transformed to active zwitterions, but that these zwitterions rapidly Add Monomer and cyclize by intramolecular backbiting of the terminal alkoxides on internal esters of the zwitterions. This cyclization event maintains the concentration of active zwitterions. The reactivation of cyclized chains by active zwitterions is a key step that leads to…

James M. Caruthers – One of the best experts on this subject based on the ideXlab platform.

  • Zwitterionic Ring-Opening Polymerization: Models for Kinetics of Cyclic Poly(caprolactone) Synthesis
    Macromolecules, 2014
    Co-Authors: Hayley A. Brown, Silei Xiong, Grigori A. Medvedev, Young A. Chang, M. Abu-omar, James M. Caruthers, Robert M. Waymouth

    Abstract:

    Investigations of the kinetics of zwitterionic ring-opening polymerization of e-caprolactone by N-heterocyclic carbenes (NHC) were carried out to illuminate the key reaction steps responsible for the formation of high molecular weight cyclic poly(caprolactones). Modeling of both the decay in Monomer concentration as well as the evolution of molecular weights and polydispersities were necessary to identify the key reaction steps responsible for initiation, propagation, cyclization and chain-transfer. Nucleophilic attack of the NHC on e-caprolactone to generate reactive zwitterions is slow and reversible. The modeling indicates that less than 60% of the carbenes are transformed to active zwitterions, but that these zwitterions rapidly Add Monomer and cyclize by intramolecular backbiting of the terminal alkoxides on internal esters of the zwitterions. This cyclization event maintains the concentration of active zwitterions. The reactivation of cyclized chains by active zwitterions is a key step that leads to…

  • Zwitterionic Ring-Opening Polymerization: Models for
    Kinetics of Cyclic Poly(caprolactone) Synthesis
    , 2014
    Co-Authors: Hayley
    A. Brown, Silei Xiong, Young A. Chang, M. Abu-omar, James M. Caruthers, Grigori
    A. Medvedev, Robert M. Waymouth

    Abstract:

    Investigations of the kinetics of
    zwitterionic ring-opening polymerization
    of ε-caprolactone by N-heterocyclic carbenes (NHC) were carried
    out to illuminate the key reaction steps responsible for the formation
    of high molecular weight cyclic poly­(caprolactones). Modeling of both
    the decay in Monomer concentration as well as the evolution of molecular
    weights and polydispersities were necessary to identify the key reaction
    steps responsible for initiation, propagation, cyclization and chain-transfer.
    Nucleophilic attack of the NHC on ε-caprolactone to generate
    reactive zwitterions is slow and reversible. The modeling indicates
    that less than 60% of the carbenes are transformed to active zwitterions,
    but that these zwitterions rapidly Add Monomer and cyclize by intramolecular
    backbiting of the terminal alkoxides on internal esters of the zwitterions.
    This cyclization event maintains the concentration of active zwitterions.
    The reactivation of cyclized chains by active zwitterions is a key
    step that leads to high molecular weight poly­(caprolactones)