Search for highly resolved electron spin resonance spectra of the transient radical in radical polymerization

Kamachi, Mikiharu

doi:10.1002/pola.10092.abs

Cited by 16 publications

(30 citation statements)

References 35 publications

(54 reference statements)

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“…[19] Under the EPR conditions of Figure 1, which have been chosen such as to avoid significant monomer conversion, only the three lines of highest intensity are seen in the upper spectrum of Figure 1. Only one single line occurs in the lower spectrum of Figure 1 for MMA-d 8 .…”

Section: Resultsmentioning

confidence: 99%

SP–PLP–EPR Investigations into the Chain‐Length‐Dependent Termination of Methyl Methacrylate Bulk Polymerization

Barth

Buback

2009

Macromol. Rapid Commun.

106

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Termination kinetics of methyl methacrylate (MMA) bulk polymerization has been studied via the single pulsed laser polymerization-electron paramagnetic resonance method. MMA-d(8) has been investigated to enhance the signal-to-noise quality of microsecond time-resolved measurement of radical concentration. Chain-length-dependent termination rate coefficients of radicals of identical size, k ti,i, are reported for 5-70 °C and up to i = 100. k ti,i decreases according to the power-law expression $k_{\rm t}^{i,i} = k_{\rm t}^{{\rm 1,1}} \cdot i^{ - \alpha }$. At 5 °C, k(t) for two MMA radicals of chain-length unity is k t1,1 = (5.8 ± 1.3) · 10(8) L · mol(-1) · s(-1) . The associated activation energy and power-law exponent are: E(A) (k t1,1) ≈ 9 ± 2 kJ · mol(-1) and α ≈ 0.63 ± 0.15, respectively.

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Section: Resultsmentioning

confidence: 99%

SP–PLP–EPR Investigations into the Chain‐Length‐Dependent Termination of Methyl Methacrylate Bulk Polymerization

Barth

Buback

2009

Macromol. Rapid Commun.

106

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“…To this end, a previously not investigated monomer, vinyl pivalate (VPi), was chosen ( Figure 1). Among the vinyl esters, vinyl acetate (VAc, Figure 1) has been subjected to k p determination using the EPR method, [29,30,73] the rotating sector method, [74] and PLP-SEC, [75] but the k p values obtained were not in agreement. The k p of vinyl neo-decanoate has been determined by PLP-SEC.…”

Section: à3mentioning

confidence: 99%

“…The EPR spectrum recorded during VPi polymerization in heptane at 60 8C is shown in Figure 3 and the spectrum of the poly(VAc) radical [30] is also shown in the same Figure for comparison. The observed spectrum is a doublet (a a ¼ 1.76 mT) of a triplet (a b ¼ 2.04 mT) without further splitting or overlapping with any other spectrum.…”

Section: Epr Detection Of Poly(vpi) Radicalmentioning

confidence: 99%

“…[26][27][28] Electron paramagnetic resonance spectroscopy (EPR) enables direct detection, identification and quantification of radical species involved in radical polymerization. [29][30][31] EPR quantification of the propagating radical concentration in conjunction with separate measurement of the overall rate of polymerization (R p ) has been utilized for k p determination of a wide range of monomers since the late 1980's. This has been aided by significant instrumental improvement in EPR sensitivity and stability of the magnetic field by computer control.…”

Section: Full Papermentioning

confidence: 99%

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Determination of the Propagation Rate Coefficient of Vinyl Pivalate Based on EPR Quantification of the Propagating Radical Concentration

Kubota

Kajiwara

Zetterlund

et al. 2007

Macro Chemistry & Physics

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The propagation rate coefficient (kp) of the vinyl pivalate (VPi) has been determined from an EPR quantification of the concentration of propagating radicals. The polymerizations followed first‐order kinetics with respect to the monomer, and the concentration of propagating radicals did not vary with time. The chain lengths were estimated to be sufficiently large to not affect kp. The resulting Arrhenius parameters for kp of VPi in heptane are Ap = 1.39 × 107 dm3 · mol−1 · s−1 and Ep = 20.5 kJ · mol−1. They are very similar to those of vinyl acetate as previously determined by the PLP method. The present results thus indicate that EPR gives consistent kp values for vinyl esters.magnified image

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“…ESR gives access to structural information via analysis of the characteristic coupling patterns and, if carried out carefully, to information on radical concentration during radical polymerization, either from steady state or from nonsteady state experiments. [49][50][51][52] The analysis of the ESR spectra and their intensity is largely complicated by signal overlap when two or more radical species coexist at any given time during the polymerization. As in ESR coupling constants are much larger than the actual shift of the centerfield with a changing radical environment, no clear separation of individual signals can be made in most cases and only overall radical concentrations can be determined.…”

Section: Direct Detection Of Mcrs Via Electron Spin Resonance Spectromentioning

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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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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Search for highly resolved electron spin resonance spectra of the transient radical in radical polymerization

Cited by 16 publications

References 35 publications

SP–PLP–EPR Investigations into the Chain‐Length‐Dependent Termination of Methyl Methacrylate Bulk Polymerization

SP–PLP–EPR Investigations into the Chain‐Length‐Dependent Termination of Methyl Methacrylate Bulk Polymerization

Determination of the Propagation Rate Coefficient of Vinyl Pivalate Based on EPR Quantification of the Propagating Radical Concentration

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

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