Effect of solvent on the rate constants in solution polymerization. Part II. Vinyl acetate

McKenna, Timothy F. L.; Villanueva, Ángeles

doi:10.1002/(sici)1099-0518(19990301)37:5<589::aid-pola8>3.0.co;2-1

Cited by 34 publications

(58 citation statements)

References 18 publications

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“…As monomer concentration increases, longer polymer chains are produced as a result of a net enhancement of the rate of polymer chain propagation (i.e., data at 60°C). This latter observation is consistent with previous studies on VAc homopolymerization in methanol, 48 toluene, 49 and ethyl acetate. 49 Experimental molecular weight data were not obtained for the grafted polymer due to the difficulty of degrafting the PVAc chains for SEC analyses.…”

Section: Molecular Weight Polymer Graft Density and Surface Topologysupporting

confidence: 94%

“…This latter observation is consistent with previous studies on VAc homopolymerization in methanol, 48 toluene, 49 and ethyl acetate. 49 Experimental molecular weight data were not obtained for the grafted polymer due to the difficulty of degrafting the PVAc chains for SEC analyses. Notwithstanding, one can estimate the molecular weight of the grafted polymer, given that the size of these chains, for free-radical graft polymerization, is expected to be similar to that of the homopolymer.…”

Section: Molecular Weight Polymer Graft Density and Surface Topologysupporting

confidence: 93%

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Graft polymerization of vinyl acetate onto silica

Nguyen

Yoshida

Cohen

2002

J of Applied Polymer Sci

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The free-radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free-radical graft polymerization of vinyl acetate in ethyl acetate with 2,2Ј-azobis(2,4-dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer-grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy-determined topology of the polymer-grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular-weight distribution for free-radical polymerization.

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Section: Molecular Weight Polymer Graft Density and Surface Topologysupporting

confidence: 94%

Section: Molecular Weight Polymer Graft Density and Surface Topologysupporting

confidence: 93%

Graft polymerization of vinyl acetate onto silica

Nguyen

Yoshida

Cohen

2002

J of Applied Polymer Sci

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“…Absolute k t 1,1 is below the numbers estimated for diffusion-limited termination of radicals with chain length unity from Equation 4 . [ 20,27,57 ] The uncertainty of the estimates via Equation 6 should not exceed ±20%.…”

Section: Combination Of Equation 7 With the Smoluchowski Equation (Eqmentioning

confidence: 99%

“…[5][6][7][8][9] Kinetic information about this effect was mostly deduced from "lumped" rate coeffi cients, such as k p / k t 0.5 , and was interpreted either as an indication of k p being affected by π-complexation of VAc macroradicals by toluene [ 5 ] or by a reduction of radical concentration by enhanced termination rate. [ 6,9 ] Jovanovic´ and Dubé, on the other hand, showed that good agreement between experimental data and model prediction may be reached by adopting signifi cant chain transfer to toluene. The resulting shorter chains are associated with higher k t giving rise to retardation as a consequence of CLDT.…”

Section: Introductionmentioning

confidence: 99%

Chain‐Length‐Dependent Termination of Vinyl Acetate and Vinyl Pivalate Bulk Homopolymerizations Studied by SP‐PLP‐EPR

Kattner

Buback

2014

Macro Chemistry & Physics

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Bulk homopolymerizations of vinyl acetate and vinyl pivalate are studied by EPR experiments between −65 °C and 60 °C with dicumyl peroxide acting as the photoinitiator. No midchain radicals are seen, which demonstrates that backbiting plays no role. The chain-length dependence of the termination rate coeffi cients measured up to 13% monomer conversion is adequately represented by the composite model. The power-law exponents α s and α l for short-chain and long-chain radicals are: α s (VAc) = 0.57 ± 0.05, α s (VPi) = 0.67 ± 0.15, α l (VAc) = 0.16 ± 0.07, and α l (VPi) = 0.16 ± 0.07. The crossover chain lengths differ largely: i c (VAc) = 20 ± 10 and i c (VPi) = 110 ± 30. The rate coeffi cient for termination of two radicals of chain length unity, k t 1,1 , which is the fourth composite-model parameter, depends on temperature, as does the monomer fl uidity.

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“…In a batch reactor, and in the absence of any gel effect, monomer conversion in a homopolymerization as a function of time is given by: ln(l-x)=_ls,__ JSf[!Jo (1-exp(-kctt)) (1) A kd 2 Iff, kd and t are known, then it is possible to estimate the value of kp/k(l_: 5 by regressing the ln(l-x) as a function ofj(t) = -kdt/2)). As can be seen in Figure 1, the lumped rate constant kP/k 1°· 5 of BuA is a function of the initial monomer concentration, even though this quantity does not appear in eq I.…”

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confidence: 99%

Effect of Solvent on the Rate Constants in Solution Polymerization III. Butyl Acrylate/Vinyl Acetate

McKenna

Heredia

1999

Polym J

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ABSTRACT:An experimental and modelling study has been carried out to explore the kinetics of the copolymerization of butyl acrylate and vinyl acetate (BuA-V Ac) in solution. A series of batch free radical copolymerization experiments has been carried out using the system BuA-VAc in an ethyl acetate (EAc) solvent. Experimental data were obtained from gravimetric and NMR measurements. The pseudo-homopolymerization constants identified in Parts I and II of this work (McKenna et a/., J. Polym. Sci., Polym. chem., in press) were used along with literature values for the propagation rate constants and reactivity ratios to model the different reactions presented here. It was found that the reactivity ratios of Dube and Penlidis [Polymer, 36, 587 (1995) With the exception of Parts 1 and 2 1 • 2 of this work, and the study published by Dube and Penlidis, 3 recent studies on the solution copolymerization of butyl acrylate (BuA) and vinyl acetate (V Ac) are scarce. And, as we have pointed out in the previous articles, even when data are available there seems to be a rather wide dispersion in reported values of the homopolymerization kinetic constants for propagation and termination, kP and k 1 • This dispersion might in part be attributable to a lack of correlation of data with reaction conditions.In a batch reactor, and in the absence of any gel effect, monomer conversion in a homopolymerization as a function of time is given by:Iff, kd and t are known, then it is possible to estimate the value of kp/k(l_: 5 by regressing the ln(l-x) as a function ofj(t) = -kdt/2)). As can be seen in Figure 1, the lumped rate constant kP/k 1°· 5 of BuA is a function of the initial monomer concentration, even though this quantity does not appear in eq I. Very similar results were observed for VAc.Note that as shown in ref 1 and 2, the values of kp/ kt 5 varied by approximately a factor of 2 over the range of concentrations studied. This means that regardless of the cause of this variation (it was proposed that chain transfer reactions were in part responsible), the radical concentration in the systems studied changed very little, and when they did change, it was not particularly rapid. Furthermore, it can also be seen from Figure 1, and from all of the curves presented in the first 2 parts of this series that the ln(1-x) is a strongly linear function of fit). This clearly demonstrates that it is reasonable to invoke the quasi-steady state assumption (QSSA) in the derivation of the equations used to analyse kp/k1°· 5 • t To whom correspondence should be addressed.Recent works have discussed the possibility that diffusion of macroradicals (i.e., chain length) might indeed be important even at low conversions in some case. 4 • 5 And since overall chain length is controlled to a large extent by monomer concentration, it is not surprising that in such a case the observed value of the rate constants should vary with the initial monomer concentration. This variation was therefore attributed, at least in part, to the fact there is a great deal of...

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Effect of solvent on the rate constants in solution polymerization. Part II. Vinyl acetate

Cited by 34 publications

References 18 publications

Graft polymerization of vinyl acetate onto silica

Graft polymerization of vinyl acetate onto silica

Chain‐Length‐Dependent Termination of Vinyl Acetate and Vinyl Pivalate Bulk Homopolymerizations Studied by SP‐PLP‐EPR

Effect of Solvent on the Rate Constants in Solution Polymerization III. Butyl Acrylate/Vinyl Acetate

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