Pulsed-laser radical polymerization and propagation kinetic parameters of some alkyl acrylates

Couvreur, Laurence; Piteau, Gwenaelle; Castignolles, Patrice; Tonge, Matthew P.; Coutin, Bernard; Charleux, Bernadette; Vairon, Jean‐Pierre

doi:10.1002/1521-3900(200109)174:1<197::aid-masy197>3.0.co;2-0

Cited by 78 publications

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“…(MA) or 80 °C 0.26 ± 0.06 [34] 0.22 [22] 0.20 ± 0.04 [34] SP PLP RAFT; bulk, Values not in brackets are from data analysis using k p estimated for polymerization in toluene, [42,43] values in brackets are from using bulk k p (see text). Note that k p does not influence the value of α l (see Equation (4) literature values adjusted to −40 °C and 1 bar using E a (k t 1,1 ) = E a (η −1 ) from Table 2 and ΔV ≠ (k t ) = −2.0 × 10 1 cm 3 ·mol −1 .…”

Section: Resultsmentioning

confidence: 74%

“…[43] Specifically, starting from the position of k p being much the same for MA under both sets of conditions, in toluene solution it decreases with increasing alkyl-group size, whereas in bulk there is the expected [44] increase. [42] These trends are sufficiently marked that for DA they seem to result in the bulk value of k p being double that in toluene solution.…”

Section: Discussionmentioning

confidence: 99%

“…[42] For these reasons we used the bulk MA value of k p to analyze both our bulk and solution data, whereas for DA in toluene we estimated k p to be half the bulk value, and it is the resulting termination parameters that we assume are more likely to be correct in the discussion that follows. At the same time, we also analyzed our DA data with the much higher bulk value of k p , because we recognize that there is still considerable uncertainty regarding the finding -based on one toluene data set only [43] -that acrylate k p have a quite different variation with size in toluene than in bulk: this has not been established definitively and is an interesting area requiring further work. The termination parameters resulting from this alternative analysis are the ones in brackets in Table 1.…”

Section: Discussionmentioning

confidence: 99%

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Chain‐Length‐Dependent Termination in Radical Polymerization of Acrylates

Barth

Buback

Russell

et al. 2011

Macro Chemistry & Physics

147

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SUMMARY:The technique of SP PLP EPR, which is single-pulse pulsed-laser polymerization (SP PLP) in conjunction with electron paramagnetic resonance (EPR) spectroscopy, is used to carry out a detailed investigation of secondary (chain-end) radical termination of acrylates. Measurements are performed on methyl acrylate, n-butyl acrylate and dodecyl acrylate in bulk and in toluene solution at -40 °C. The reason for the low temperature is to avoid formation of mid-chain radicals, a complicating factor that has imparted ambiguity to the results of previous studies of this nature. Consistent with these previous studies, composite-model behavior for chain-length-dependent termination rate, is found in this work. However, lower and more reasonable values of α s , the exponent for variation of k t i,i at short chain lengths, are found in the present study.

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Section: Resultsmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Chain‐Length‐Dependent Termination in Radical Polymerization of Acrylates

Barth

Buback

Russell

et al. 2011

Macro Chemistry & Physics

147

View full text Add to dashboard Cite

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“…The most comprehensive data set for k p exists for butyl acrylate, where an IUPAC working party collated all available data in a benchmark paper. 33 The 62,81,83 to name a few important examples. Inspection of these references indicates that the variation in propagation rate coefficients within the acrylate monomer family (at an identical temperature) is less than a factor of two.…”

Section: Determination Of Individual Rate Coefficientsmentioning

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.

212

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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“…The k p and k t values for EHA are smaller than for tBA by about one order of magnitude. However, the k p values obtained by PLP-GPC for tBA and EHA at 60 8C (calculated from the Arrhenius parameters at 0 8C where any effects of MCR are believed to be negligible; k p (tBA) ¼ 2.5 Â 10 4 L Á mol Á s À1 [32] and k p (EHA) ¼ 3.9 Â 10 4 L Á mol Á s À1 [33] ) differ by less than a factor of two. The significantly greater difference between the k p values obtained by the PLP-GPC and EPR methods in the case of EHA polymerization implies that the k p value for EHA obtained by the EPR method is more strongly affected by MCR than tBA.…”

Section: Determination Of Apparent K P and K T Valuesmentioning

confidence: 99%

Influence of Mid‐Chain Radicals on Acrylate Free Radical Polymerization: Effect of Ester Alkyl Group

Sato

Emoto

Zetterlund

et al. 2004

Macro Chemistry & Physics

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Summary: The benzene solution polymerizations of tert‐butyl acrylate (tBA) and 2‐ethylhexyl acrylate (EHA) have been investigated with respect to the effects of mid‐chain radicals (MCRs) on the rate of polymerization, the total radical concentration, the apparent rate coefficients for propagation, termination, and β‐fragmentation, the contents of unsaturated end groups and branching, and the molecular weight distribution. The EHA polymerization involves a considerably higher concentration of MCR and is more significantly affected by MCR than the tBA polymerization. The MCR content as estimated by electron paramagnetic resonance (EPR) spectroscopy during photosensitized EHA polymerization was as high as 70% of the total radical concentration at 25 °C. However, no 1H and 13C NMR resonances due to unsaturated ends and branching, respectively, were detected for the poly(EHA) obtained at 25 °C. These findings indicate that a high MCR content does not directly correspond to significant MCR effects on the polymer structure. The rate constants for mutual reaction ($k'_{\rm t}$) and β‐fragmentation (kf) of MCR were estimated for the two assumed cases where MCR was consumed solely by (i) mutual reaction, and (ii) β‐fragmentation, based on the after‐effect of the photosensitized EHA polymerization monitored by EPR spectroscopy at 25 °C; $k'_{\rm t}$ = 3.5 × 103 L · mol · s−1 and kf = 4.2 × 10−2 s−1. These rate coefficients were compared with those for reactions of structurally similar radicals.

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Pulsed-laser radical polymerization and propagation kinetic parameters of some alkyl acrylates

Cited by 78 publications

References 0 publications

Chain‐Length‐Dependent Termination in Radical Polymerization of Acrylates

Chain‐Length‐Dependent Termination in Radical Polymerization of Acrylates

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

Influence of Mid‐Chain Radicals on Acrylate Free Radical Polymerization: Effect of Ester Alkyl Group

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