The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Thomas P Davis - One of the best experts on this subject based on the ideXlab platform.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Macromolecules, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-...
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modeling the reversible addition fragmentation chain transfer process in cumyl dithiobenzoate mediated styrene homopolymerizations assessing rate coefficients for the addition fragmentation equilibrium
Journal of Polymer Science Part A, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, David Robert Morsley, Thomas P DavisAbstract:A full kinetic scheme for the free-radical reversible addition-fragmentation chain transfer (RAFT) process is presented and implemented into the program package PREDICI (R). With the cumyl dithiobenzoate-mediated bulk polymerization of styrene at 60 degreesC as an example, the rate coefficients associated with the addition-fragmentation equilibrium are deduced by the careful modeling of the time-dependent evolution of experimental molecular weight distributions. The rate coefficient for the addition reaction of a free macroradical to a polymeric RAFT species (k(beta)) is approximately 5 . 10(5) L mol(-1) s(-1), whereas the fragmentation rate coefficient of the formed macroradical RAFT species is close to 3 . 10(-2) s(-1). These values give an equilibrium constant of K = k(beta)/k(-beta) = 1.6 . 10(7) L mol(-1). Conclusive evidence is given that the equilibrium lies well on the side of the macroradical RAFT species. The high value of k(beta) is comparable in size to the propagation rate coefficients reported for acrylates. The transfer rate coefficient to cumyl dithiobenzoate is close to 3.5 . 10(5) L mol(-1) s(-1). A careful sensitivity analysis was performed, which indicated that the reported rate coefficients are accurate to a factor of 2. (C) 2001 John Wiley & Sons, Inc.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Institute for Future Environments; Science & Engineering Faculty, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-1 s-1. The MMA system has been studied over the temperature range 25-60 °C. The hybrid behavior observed in the MMA polymerizations has been exploited (at low monomer conversions) to perform a Mayo analysis allowing the determination of the temperature dependence of the transfer to cumyl phenyldithioacetate reaction. The activation energy of this process is close to 26 kJ mol-1. In contrast to the styrene system, the PREDICI simulation procedure cannot be successfully applied to cumyl phenyldithioacetate mediated MMA polymerizations for the deduction of kβ and k-β. This inability is due to the hybrid nature of the cumyl phenyldithioacetate-MMA system, leading to a significantly reduced sensitivity toward kβ and k-β.
Christopher Barnerkowollik - One of the best experts on this subject based on the ideXlab platform.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Macromolecules, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-...
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modeling the reversible addition fragmentation chain transfer process in cumyl dithiobenzoate mediated styrene homopolymerizations assessing rate coefficients for the addition fragmentation equilibrium
Journal of Polymer Science Part A, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, David Robert Morsley, Thomas P DavisAbstract:A full kinetic scheme for the free-radical reversible addition-fragmentation chain transfer (RAFT) process is presented and implemented into the program package PREDICI (R). With the cumyl dithiobenzoate-mediated bulk polymerization of styrene at 60 degreesC as an example, the rate coefficients associated with the addition-fragmentation equilibrium are deduced by the careful modeling of the time-dependent evolution of experimental molecular weight distributions. The rate coefficient for the addition reaction of a free macroradical to a polymeric RAFT species (k(beta)) is approximately 5 . 10(5) L mol(-1) s(-1), whereas the fragmentation rate coefficient of the formed macroradical RAFT species is close to 3 . 10(-2) s(-1). These values give an equilibrium constant of K = k(beta)/k(-beta) = 1.6 . 10(7) L mol(-1). Conclusive evidence is given that the equilibrium lies well on the side of the macroradical RAFT species. The high value of k(beta) is comparable in size to the propagation rate coefficients reported for acrylates. The transfer rate coefficient to cumyl dithiobenzoate is close to 3.5 . 10(5) L mol(-1) s(-1). A careful sensitivity analysis was performed, which indicated that the reported rate coefficients are accurate to a factor of 2. (C) 2001 John Wiley & Sons, Inc.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Institute for Future Environments; Science & Engineering Faculty, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-1 s-1. The MMA system has been studied over the temperature range 25-60 °C. The hybrid behavior observed in the MMA polymerizations has been exploited (at low monomer conversions) to perform a Mayo analysis allowing the determination of the temperature dependence of the transfer to cumyl phenyldithioacetate reaction. The activation energy of this process is close to 26 kJ mol-1. In contrast to the styrene system, the PREDICI simulation procedure cannot be successfully applied to cumyl phenyldithioacetate mediated MMA polymerizations for the deduction of kβ and k-β. This inability is due to the hybrid nature of the cumyl phenyldithioacetate-MMA system, leading to a significantly reduced sensitivity toward kβ and k-β.
Guy Marin - One of the best experts on this subject based on the ideXlab platform.
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how chain length dependencies interfere with the bulk raft polymerization rate and microstructural control
Chemical Engineering Science, 2018Co-Authors: Nils De Rybel, Paul H. M. Van Steenberge, Dagmar R Dhooge, Marie-françoise Reyniers, Guy MarinAbstract:Abstract A pseudo-steady state based (PSSA) deterministic solution strategy is presented to calculate the concentrations of single and multi-arm macrospecies types in reversible addition fragmentation chain transfer (RAFT) polymerization, accounting for chain length dependent apparent rate coefficients to fully reflect the impact of diffusional limitations. The simulation time is of minute scale and diffusional limitation on termination are accounted for with the RAFT-chain length dependent-termination technique. Based on an extensive set of experimental data (18 conditions), addition and fragmentation kinetic parameters are determined for RAFT polymerization of styrene initiated by 2,2′-azobis(2-methylpropionitrile) and 2-cyano-2-propyl dodecyl trithiocarbonate. Due to higher chain length dependent apparent termination rates, a rate retardation with respect to the free radical polymerization (FRP) results despite that a simplified degenerative mechanism can be considered. This rate retardation is enhanced for polymerizations exhibiting a stronger gel-effect ( e.g. methyl methacrylate). Then even the average RAFT polymerization characteristics cannot be reliably calculated by approximating the macroradical chain length distribution (CLD) through a Poisson or Schulz-Flory distribution. The calculation of the macroradical CLD always requires a full kinetic model taking into account the chain length dependencies for all individual chain lengths.
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estimation of intrinsic rate coefficients in vinyl chloride suspension polymerization
Polymer, 2005Co-Authors: Joris Wieme, Geraldine Heynderickx, Guy MarinAbstract:Abstract The pre-exponential factor and the activation energy of the intrinsic rate coefficients for propagation, chain transfer to monomer, chain initiation by a Cl radical and termination in the suspension polymerization of vinyl chloride are estimated by regression of experimental data for the monomer conversion, ranging from 3 to 85%, and for the moments of the molecular mass distribution as a function of batch time over the temperature range of 308–338 K and for initiator ( tert -butyl peroxyneodecanoate) concentrations from 0.026 to 3.0 wt%, based on the monomer. Termination by combination is the dominant termination mechanism. Cl radicals, formed in the chain transfer to monomer, contribute to the termination by recombination with Macroradicals and, hence, attenuate the gel effect. Physically meaningful and statistically significant estimates for the pre-exponential factors and activation energies, 24.9 kJ mol −1 for propagation and 54.3 kJ mol −1 for chain transfer, allow to describe the experimental data over the full range of investigated conditions.
John F Quinn - One of the best experts on this subject based on the ideXlab platform.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Macromolecules, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-...
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modeling the reversible addition fragmentation chain transfer process in cumyl dithiobenzoate mediated styrene homopolymerizations assessing rate coefficients for the addition fragmentation equilibrium
Journal of Polymer Science Part A, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, David Robert Morsley, Thomas P DavisAbstract:A full kinetic scheme for the free-radical reversible addition-fragmentation chain transfer (RAFT) process is presented and implemented into the program package PREDICI (R). With the cumyl dithiobenzoate-mediated bulk polymerization of styrene at 60 degreesC as an example, the rate coefficients associated with the addition-fragmentation equilibrium are deduced by the careful modeling of the time-dependent evolution of experimental molecular weight distributions. The rate coefficient for the addition reaction of a free macroradical to a polymeric RAFT species (k(beta)) is approximately 5 . 10(5) L mol(-1) s(-1), whereas the fragmentation rate coefficient of the formed macroradical RAFT species is close to 3 . 10(-2) s(-1). These values give an equilibrium constant of K = k(beta)/k(-beta) = 1.6 . 10(7) L mol(-1). Conclusive evidence is given that the equilibrium lies well on the side of the macroradical RAFT species. The high value of k(beta) is comparable in size to the propagation rate coefficients reported for acrylates. The transfer rate coefficient to cumyl dithiobenzoate is close to 3.5 . 10(5) L mol(-1) s(-1). A careful sensitivity analysis was performed, which indicated that the reported rate coefficients are accurate to a factor of 2. (C) 2001 John Wiley & Sons, Inc.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Institute for Future Environments; Science & Engineering Faculty, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-1 s-1. The MMA system has been studied over the temperature range 25-60 °C. The hybrid behavior observed in the MMA polymerizations has been exploited (at low monomer conversions) to perform a Mayo analysis allowing the determination of the temperature dependence of the transfer to cumyl phenyldithioacetate reaction. The activation energy of this process is close to 26 kJ mol-1. In contrast to the styrene system, the PREDICI simulation procedure cannot be successfully applied to cumyl phenyldithioacetate mediated MMA polymerizations for the deduction of kβ and k-β. This inability is due to the hybrid nature of the cumyl phenyldithioacetate-MMA system, leading to a significantly reduced sensitivity toward kβ and k-β.
Johan P A Heuts - One of the best experts on this subject based on the ideXlab platform.
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Macromolecules, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-...
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kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate
Institute for Future Environments; Science & Engineering Faculty, 2001Co-Authors: Christopher Barnerkowollik, John F Quinn, T L U Nguyen, Johan P A Heuts, Thomas P DavisAbstract:A previously published simulation and data fitting procedure for the reversible addition fragmentation chain transfer (RAFT) process using the PREDICI simulation program has been extended to cumyl phenyldithioacetate mediated styrene and methyl methacrylate (MMA) bulk homopolymerizations. The experimentally obtained molecular weight distributions (MWDs) for the styrene system are narrow and unimodal and shift linearly with monomer conversion to higher molecular weights. The MMA system displays a hybrid of conventional chain transfer and living behavior, leading to bimodal MWDs. The styrene system has been subjected to a combined experimental and modeling study at 60 °C, yielding a rate coefficient for the addition reaction of free Macroradicals to polymeric RAFT agent, kβ, of approximately 5.6 × 105 L mol-1 s-1 and a decomposition rate coefficient for macroradical RAFT species, k-β, of about 2.7 × 10-1 s-1. The transfer rate coefficient to cumyl phenyldithioacetate is found to be close to 2.2 × 105 L mol-1 s-1. The MMA system has been studied over the temperature range 25-60 °C. The hybrid behavior observed in the MMA polymerizations has been exploited (at low monomer conversions) to perform a Mayo analysis allowing the determination of the temperature dependence of the transfer to cumyl phenyldithioacetate reaction. The activation energy of this process is close to 26 kJ mol-1. In contrast to the styrene system, the PREDICI simulation procedure cannot be successfully applied to cumyl phenyldithioacetate mediated MMA polymerizations for the deduction of kβ and k-β. This inability is due to the hybrid nature of the cumyl phenyldithioacetate-MMA system, leading to a significantly reduced sensitivity toward kβ and k-β.
