The role of monomer in the chain transfer reaction in cobaloxime-mediated free-radical polymerization

Heuts, Johan P. A.; Forster, Darren J.; Davis, Thomas P.

doi:10.1002/(sici)1521-3927(19990601)20:6<299::aid-marc299>3.0.co;2-o

Cited by 17 publications

(5 citation statements)

References 9 publications

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“…Kukulj et al16 suggested that the continuously changing ratio of monomer to solvent may be a possible explanation for decreasing catalyst activity. However, Heuts et al18 tested this hypothesis by determining the chain transfer coefficients from experiments at constant catalyst concentrations and varying monomer concentrations and did not obtain any evidence in support of this hypothesis. Results on solvent effects, in which C T proved to be independent of toluene concentration, as discussed in a previous article29 point in the same direction.…”

Section: Resultsmentioning

confidence: 99%

“…Some other studies were mainly focused on the production of dimer at high catalyst concentrations and subsequent copolymerization with other monomers 14, 15. Most kinetic studies were carried out in the group of Davis and Heuts 16–22. For nearly all studies molecular weight distributions did not or hardly change with conversion, whereas a decrease, which would be expected according to the Mayo equation (1), was only observed experimentally by Kowollik et al20 Several explanations have been suggested like catalyst deactivation and catalyst–solvent interactions that change with conversion and compensate for a decrease in monomer concentration.…”

Section: Introductionmentioning

confidence: 99%

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High‐conversion catalytic chain transfer polymerization of methyl methacrylate

Pierik

Herk

2003

J of Applied Polymer Sci

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ABSTRACT:In this work the effects of conversion on the apparent catalyst activity in the catalytic chain transfer polymerization of methyl methacrylate are reported. Several mechanisms are discussed that may explain the experimental observations. The discussion is supported with computer simulations using Predici software. It is shown that the experimental decrease in weight average molecular weight with conversion is smaller than the decrease obtained in simulations. The most likely cause for this discrepancy is slow catalyst deactivation. The half-life of CoBF under the reported conditions was determined to be about 10 h. Furthermore, the effect of acetic acid (HAc) and benzoyl peroxide (BPO) on the evolution of the molecular weight distribution is investigated. Both HAc and BPO enhance catalyst deactivation. For HAc, catalyst deactivation scales with the square root of its concentration. BPO-enhanced deactivation depends linearly on its concentration.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High‐conversion catalytic chain transfer polymerization of methyl methacrylate

Pierik

Herk

2003

J of Applied Polymer Sci

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“…Gridnev [32] reported a similar effect of monomer purity on C T . Heuts et al [33] found that values in bulk and solution were almost the same only for Co(Ph) 4 BF, a tetraphenyl cobaloxime derivative. In that study both toluene and tertbutyl acetate were chosen as solvents, as no solvent complexation effects were expected.…”

Section: Effects Of Solvents and Solvent Impuritiesmentioning

confidence: 99%

Solvent Effects, Diffusion Control and Mechanistic Aspects of Catalytic Chain Transfer Polymerization

Pierik¹,

Vollmerhaus²,

Herk³

2003

Macro Chemistry & Physics

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In the catalytic chain transfer polymerization of methyl methacrylate, butyl methacrylate and 2‐ethylhexyl methacrylate in toluene, it was found that the chain transfer constants (CT) were independent of solvent concentration and therefore of solution viscosity, and did not differ from the bulk polymerization values. For a diffusion controlled system, theoretical calculations predict an increase in CT when the solution viscosity is lowered. This points at a non‐diffusion controlled catalytic chain transfer step. These results were obtained when the solvent was thoroughly purified using a Grubbs‐type set‐up, whereas a large reduction in CT was found in unpurified solvent. Similar results were obtained for butyl acetate. Therefore it is concluded that the decrease of CT in non‐purified solvents is not related to the solvent itself, but to solvent impurities. Further we found that methyl methacrylate ended radicals do not covalently bind to the cobalt complex, in contrast to styrene and acrylate ended radicals.Chain transfer constant for the CCT polymerization of 2‐ethylhexyl methacrylate in toluene, and predictions for diffusion controlled systems.magnified imageChain transfer constant for the CCT polymerization of 2‐ethylhexyl methacrylate in toluene, and predictions for diffusion controlled systems.

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“…(3)). This is clearly not observed and a plausible explanation for this result [19] other than (fortuitous) catalyst poisoning, [20,21] is not available at present. A summary of the final molecular weight parameters obtained from all the polymerizations is given in Tab.…”

Section: Molecular Weight Evolutionmentioning

confidence: 99%

Preparation and characterization of oligomeric terpolymers of styrene, methyl methacrylate and 2-hydroxyethyl methacrylate: A comparison of conventional and catalytic chain transfer

Heuts

Muratore

Davis

2000

Macromol. Chem. Phys.

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Batch solution terpolymerizations of styrene, methyl methacrylate and 2‐hydroxyethyl methacrylate were carried out at 70°C in the presence of either dodecanethiol or bis[(difluoroboryl)diphenylglyoximato]cobalt‐(II) (COPhBF), to yield polymer products with a number average molecular weight of about 2 500. Conversion, molecular weight distribution and overall composition were monitored during the reaction, and the final products were investigated using differential scanning calorimetry and thermogravimetric analysis. It was found that the overall rates of polymerization do not differ significantly in the two systems, but that the molecular weight distribution of the polymer formed in the presence of the thiol becomes increasingly broader during the polymerization, whereas the COPhBF‐mediated polymerization produces a relatively uniform product during the course of the reaction. The polymer product formed with COPhBF was found to be slightly less thermally stable than the product formed by the thiol, which can be explained by the formation of unsaturated endgroups in the case of the former product.

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The role of monomer in the chain transfer reaction in cobaloxime-mediated free-radical polymerization

Cited by 17 publications

References 9 publications

High‐conversion catalytic chain transfer polymerization of methyl methacrylate

High‐conversion catalytic chain transfer polymerization of methyl methacrylate

Solvent Effects, Diffusion Control and Mechanistic Aspects of Catalytic Chain Transfer Polymerization

Preparation and characterization of oligomeric terpolymers of styrene, methyl methacrylate and 2-hydroxyethyl methacrylate: A comparison of conventional and catalytic chain transfer

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