Chain Transfer to Polymer in Free-Radical Solution Polymerization of 2-Ethylhexyl Acrylate Studied by NMR Spectroscopy

Heatley, Frank; Lovell, Peter A.; Yamashita, Tsuyoshi

doi:10.1021/ma0101299

Cited by 95 publications

(139 citation statements)

References 11 publications

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“…With aliphatic acrylates, only the type of MCRs as shown in Scheme 1 will play a significant role. 17 MCRs can in principle be generated by three distinctly different inter-or intramolecular reaction pathways. As stated earlier, the transfer products of all three pathways are identical in electronic nature and in their direct chemical neighborhood.…”

Section: Formation Of Mcr and Follow-on Reactionsmentioning

confidence: 99%

“…From the abundance of quaternary carbons they deduced the branching frequency and concluded that the origin of these branches must be inter-and more notably intramolecular transfer to polymer reactions [17][18][19] giving a late confirmation for the backbiting theory. [8][9][10] Parallel to the investigations into the level of branching in acrylate polymerizations, difficulties in the determination of the propagation rate coefficient, k p , for alkyl acrylates became apparent.…”

Section: Introductionmentioning

confidence: 99%

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The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Junkers

Barner‐Kowollik

2008

J. Polym. Sci. A Polym. Chem.

213

326

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The past 5 years have seen a significant increase in the understanding of the fate of so‐called mid‐chain radicals (MCR), which are formed during the free radical polymerization of monomers that form highly reactive propagating radicals and contain an easily abstractable hydrogen atom. Among these monomers, acrylates are, beside ethylene, among the most prominent. Typically, a secondary propagating acrylate‐type macroradical (SPR) can easily transfer its radical functionality via a six‐membered transition state to a position within the polymer chain (in a so‐called backbiting reaction), creating a tertiary MCR. Alternatively, the radical function can be transferred intramolecularly to any position within the chain (also forming an MCR) or intermolecularly to another polymer strand. This article aims at providing a comprehensive overview of the up‐to‐date knowledge about the rates at which MCRs are formed, their secondary reactions as well as the consequences of their occurrence under variable reaction conditions. We explore the latest aspects of their detection (via electron spin resonance spectroscopy) as well as the characterization of the polymer structures to which they lead (via high resolution mass spectrometry). The presence of MCRs leads to the formation of branched polymers and the partial formation of polymer networks. They also limit the measurement of kinetic parameters (such as the SPR propagation rate coefficient) with conventional methods. However, their occurrence can also be used as a synthetic handle, for example, the high‐temperature preparation of macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7585–7605, 2008

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Section: Formation Of Mcr and Follow-on Reactionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Junkers

Barner‐Kowollik

2008

J. Polym. Sci. A Polym. Chem.

213

326

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“…Similar investigations of free-radical processes with a high rate of chain transfer to polymer include the free-radical solution polymerization of butyl acrylate, [18] 2-ethylhexyl acrylate [19] and free-radical and bulk polymerization of vinyl acetate. [20] Termination by combination and disproportionation are included in the model, as well as chain transfer to monomer and solvent.…”

Section: Reaction Mechanismmentioning

confidence: 99%

Calculation of Molecular Weight Distributions in Non-Linear Free-Radical Polymerization Using the Numerical Fractionation Technique

Papavasiliou

Birol

Teymour³

2002

Macromol. Theory Simul.

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Mathematical Modeling of non‐linear polymerization systems subject to gel formation is a challenging endeavor. At the gel point, the second and higher molecular weight moments diverge to infinity making it impossible to obtain the molecular weight distribution (MWD). The numerical fractionation (NF) technique utilizes a refinement of the method of moments to model non‐linear polymerization systems that form gel. Since the method of moments yields results in terms of average quantities, some information is lost when reconstructing the MWD using NF. As a consequence, a broad shoulder appears at the high chain length end of the MWD tail. This study demonstrates that the validity of the gamma distribution deteriorates for the broader branched polymer generations and evaluates the performance of various alternative model distributions. Proper selection of the model distribution enhances the NF‐reconstructed MWD.

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“…[28] Indirect evidence of branching, by the loss of PLP-structure in polymer MMDs, is documented for a wide range of alkyl acrylates [2,[8][9][10][29][30][31][32] as well as AA. [33,34] Application of a 500 Hz laser extends the temperature range over which chain-end propagation may be measured using the PLP-SEC technique; [9] however, the loss of PLP structure in the polymer MMDs at 70-80 8C is still attributed to the effect of backbiting not only for BA, [9] but also for isobornyl acrylate, tert-butyl acrylate and 1-ethoxyethyl acrylate, [35] and a series of carbamate acrylates.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Hydrogen Bonding on Intramolecular Chain Transfer in Polymerization of Acrylates

Liang

Hutchinson

2011

Macromol. Rapid Commun.

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Propagation rate coefficients (k(p) ) for 2-hydroxyethyl acrylate (HEA) have been determined by pulsed-laser polymerization (PLP) combined with size-exclusion chromatography (SEC) between 20 and 60 °C using pulse repetition rates of 50 and 100 Hz. The success of PLP-SEC under these conditions suggests that HEA is not subjected to the intramolecular chain transfer to polymer (backbiting) reactions dominant for other acrylates; (13) C NMR analysis shows that the quaternary carbon observed in PLP-generated poly(butyl acrylate) (pBA) samples is not observed in pHEA. These results are related to H-bonding in the system, as it is shown that the introduction of H-bonding by addition of n-butanol to BA suppresses backbiting, and the disruption of H-bonding by addition of dimethylformamide to HEA leads to an increased level of backbiting.

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Chain Transfer to Polymer in Free-Radical Solution Polymerization of 2-Ethylhexyl Acrylate Studied by NMR Spectroscopy

Cited by 95 publications

References 11 publications

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Calculation of Molecular Weight Distributions in Non-Linear Free-Radical Polymerization Using the Numerical Fractionation Technique

The Effect of Hydrogen Bonding on Intramolecular Chain Transfer in Polymerization of Acrylates

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