Pulsed initiation polymerization as a means of obtaining propagation rate coefficients in free-radical polymerizations. II Review up to 2000

Herk, Alex M. van

doi:10.1002/1521-3919(20001101)9:8<433::aid-mats433>3.0.co;2-i

Cited by 100 publications

(59 citation statements)

References 77 publications

(121 reference statements)

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“…14 The bigger difference between the Mw of BrPMAAm and FMAAm could be explained by using the Br-styrene and Fstyrene propagation rate constant in which Br-Sty has a bigger k p value than F-Sty. 28 Furthermore, flour is more active than bromine as a radical, and so flour, like a chain transfer agent, can cause a decrease in the 29 In the nanocomposite of BrPMAAm, molecular weight was less than that of the homopolymer of BrPMAAm, but nanocomposite of FPMAAm molecular weight was higher than that of homopolymer of FPMAAm. HI values indicated that the polymerization process is ideal for polymer nanocomposites.…”

Section: Gpc Analysesmentioning

confidence: 99%

Synthesis and characterization of halogen-containing aryl amide polymer-clay nanocomposites

Delibaş¹,

Alparslan²

2015

Turk J Chem

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Synthesized N -(4-bromophenyl)-2-methacrylamide (BrPMAAm) and N -(4-fluorophenyl)-2-methacrylamide (FPMAAm) monomers were polymerized via free radical polymerization. Montmorillonite-containing raw clay (NaMT) was purified to obtain pristine clay (SMT). XRF results of the SMT sample showed that sodium amount increased and so it is sodium montmorillonite. Using the SMT and organic surfactant hexadecyltrimethylammonium bromide (CTAB), organoclay (OSMT) was synthesized. d 001 interlayer distances were 1.4967 nm and 2.0439 nm for SMT and OSMT, respectively. Composites of BrPMAAm and FPMAAm monomers were obtained using 2%, 4%, 6%, and 10% organoclay by in situ polymerization. Molecular weights for poly(BrPMAAm), poly(BrPMAAm)-10%OSMT, poly(FPMAAm), and poly(FPMAAm)-10%OSTM were 91,300, 31,300, 17,400, and 23,700, respectively. Thermal properties of the nanocomposite were also developed when compared to the pure homopolymer. The beginning thermal decomposition temperature of nanocomposites was shifted to higher temperature. An exfoliated structure was found for the nanocomposites.

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Section: Gpc Analysesmentioning

confidence: 99%

Synthesis and characterization of halogen-containing aryl amide polymer-clay nanocomposites

Delibaş¹,

Alparslan²

2015

Turk J Chem

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“…The discovery of the revolutionary pulsed laser polymerization (PLP) technique to obtain accurate values of k p for a wide range of monomers in the 1980s led to much greater correlation between experiment and prediction for the rate of polymerization and evolution of the MWD. 2 It was found that k p was relatively constant over the conversion profile (in bulk up to 80% conversion), and is relatively unaffected by the reaction mixture's viscosity. However, the equally important bimolecular termination rate coefficient (k t ) for the reaction between two propagating radicals constantly changes with reaction viscosity, type of polymer matrix, chain length of the polymeric radicals, and many other factors that are all intrinsically linked.…”

Section: Introductionmentioning

confidence: 99%

Bimolecular radical termination: New perspectives and insights

Johnston‐Hall

Monteiro

2008

J. Polym. Sci. A Polym. Chem.

132

216

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ABSTRACT:The reversible addition-fragmentation chain transfer-chain length dependent termination (RAFT-CLD-T) method has allowed us to answer a number of fundamental questions regarding the mechanism of diffusion-controlled bimolecular termination in free-radical polymerization (FRP). We carried out RAFTmediated polymerizations of methyl acrylate (MA) in the presence of a star matrix to develop an understanding of the effect of polymer matrix architecture on the termination of linear polyMA radicals and compared this to polystyrene, polymethyl methacrylate, and polyvinyl acetate systems. It was found that the matrix architecture had little or no influence on termination in the dilute regime.However, due to the smaller hydrodynamic volumes of the stars in solution compared to linear polymer of the same molecular weight, the gel onset point occurred at greater conversions, and supported the postulate that chain overlap (or c*) is the main cause for the observed autoacceleration observed in FRP. Other theories based on \short-long" termination or free-volume should be disregarded. Additionally, since our systems are well below the entanglement molecular weight, entanglements should also be disregarded as the cause of the gel onset. The semidilute regime occurs over a small conversion range and is difficult to quantify. However, we obtain accurate dependencies for termination in the concentrated regime, and observed that the star polymers (through the tethering of the arms) provided constriction points in the matrix that significantly slow the diffusion of linear polymeric radicals. Although, this could at first sight be postulated to be due to reptation, the dependencies showed that reptation could be considered only at very high conversions (close to the glass transition regime). In general, we find from our data that the polymer matrix is much more mobile than what is expected if reptation were to dominate.

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“…[3,4] carried out in a non-steady state, then the rate will instead yield k p /k t , still enabling k t to be easily obtained. [5,6] This has opened up hope that many of the frustrations associated with k t , a centrally important parameter, will be resolved.…”

Section: Some Introductory Thoughtsmentioning

confidence: 99%

The Cutthroat Competition Between Termination and Transfer to Shape the Kinetics of Radical Polymerization

Smith

Russell

2007

Macromolecular Symposia

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Summary:There is a fascinating interplay between termination and transfer that shapes the kinetics of radical polymerization (RP). In one limit all dead-chain formation is by termination, in the other by transfer. Because of chain-lengthdependent termination (CLDT), the rate law for RP takes a different form in each limit. However, common behavior is observed if one instead considers how the average termination rate coefficient varies with average degree of polymerization. Examples are given of using these principles to understand trends in actual RP data, and it is also demonstrated how to extract quantitative information on CLDT from simple steady-state experiments.Keywords: chain transfer; kinetics (polym.); radical polymerization; termination Some Introductory ThoughtsThe steady-state rate of radical polymerization (RP) is given byHere c M is monomer concentration, t time, k p propagation rate coefficient, R init rate of initiation, and k t termination rate coefficient. Measurement of initiator decomposition rates, and thus specification of R init , has never been a problem. However for much of the history of RP, the disentangling of k p and k t was a problem. This was solved in 1987 when it was shown that by relatively simple analysis of the molecular weight distribution from a pulsed-laser polymerization (PLP), the value of k p could be obtained without requirement for any knowledge of k t (or R init ).[1] So enthusiastically and successfully was this method adopted by the RP community that within just a few years it was recommended by an IUPAC WorkingParty as the method of choice for k p determination; [2] recent reviews emphasize just how widely the method has been deployed. [3,4]

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Pulsed initiation polymerization as a means of obtaining propagation rate coefficients in free-radical polymerizations. II Review up to 2000

Cited by 100 publications

References 77 publications

Synthesis and characterization of halogen-containing aryl amide polymer-clay nanocomposites

Synthesis and characterization of halogen-containing aryl amide polymer-clay nanocomposites

Bimolecular radical termination: New perspectives and insights

The Cutthroat Competition Between Termination and Transfer to Shape the Kinetics of Radical Polymerization

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