ESR Study of the Propagating Radical in the Polymerization of MMA in Frozen State

Kamachi, Mikiharu; Kohno, Masahiro; Liaw, Der Jang; Katsuki, Shuhei

doi:10.1295/polymj.10.69

Cited by 48 publications

(13 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The MMA spectrum observed at 77 K changed to the 9 line pattern in Figure 4 at 123 K. Similar irreversible changes have been observed for example in the benzoyl peroxide (BPO)-initiated polymerization of MMA in frozen aromatic solvents [48]. The nine lines, designated as the 5 + 4 lines were assigned to the propagating radical -CH 2 Ċ(CH 3 )R. Details about the radical were obtained from the shape of the spectrum, especially the relative intensity of the lines which has been interpreted in terms of various factors such as that there is more than one conformation [49], there is a distribution of dihedral angles for a single conformation [45] or a site exchange motion around the -CH 2 -Ċ< bond [50].…”

Section: Radical Reactionssupporting

confidence: 76%

Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state

Lund

Danilczuk

2012

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

View full text Add to dashboard Cite

Electron paramagnetic resonance (EPR) spectroscopy was applied to study the paramagnetic species formed from styrene, 1,1-diphenylethylene, α-methylstyrene, β-methylstyrene and methylmethacrylate adsorbed on amorphous silica gel after -irradiation at 77 K. Radicals formed by the hydrogen atom addition at the vinyl group of the monomers were observed in all samples. The hydrogen atoms were shown to originate to a large extent from the adsorbent by using silica gel with deuterated silanol groups. An EPR spectrum assigned to a propagating radical was observed at increased temperature for samples containing methylmethacrylate (MMA). The structures of the adsorption complexes, the respective hyperfine coupling constants and the adsorption energies were calculated by applying DFT quantum chemical methods. The reaction between an MMA molecule and the MMA radical and the structure of the propagating radical was modeled. The calculated hyperfine coupling constants for all radicals confirmed the assignment of the experimental spectra.3

show abstract

Section: Radical Reactionssupporting

confidence: 76%

Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state

Lund

Danilczuk

2012

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

View full text Add to dashboard Cite

show abstract

“…Well-known 9-line ESR spectra of MMA are shown in Figure 1, which indicates that their line shapes depend on the solvent used. 41 However, the spectral pattern in the frozen state is influenced by complicated factors, such as the anisotropy of the g factor and hfc's, and no information on the propagating radical could be obtained from the differences in the spectral pattern.…”

Section: Background On Esr Studymentioning

confidence: 99%

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

Kamachi

2002

J. Polym. Sci. A Polym. Chem.

Self Cite

View full text Add to dashboard Cite

ABSTRACT:The detection of highly resolved spectra in electron spin resonance (ESR) measurements of radical polymerization is presented. Well-resolved ESR spectra of the propagating radical were detected in the radical polymerization of several vinyl monomers with a specially designed cavity and cell. More highly resolved ESR spectra of the propagating radicals of vinyl and diene compounds were observed with aconventional spectrometer without the specially designed cavity and cell. On the basis of the ESR spectra, propagation rate constants and dynamic behavior of propagating radicals are discussed. Moreover, the application of time-resolved ESR spectroscopy to research on the initiation process in radical polymerization is shown.

show abstract

“…Benzyl methacrylate (BzMA), and isobutyl methacrylate (iBMAl were purified by the same method as MMA. 2 Benzoyl peroxide was repeatedly recrystallized from ethanol and dried in vacuo.…”

mentioning

confidence: 99%

ESR Observation of Methacrylate Propagating Radicals in Stationary State

Kamachi

Kohno²,

Kuwae

et al. 1982

Polym J

Self Cite

View full text Add to dashboard Cite

Considerable data on the propagation and termination rate constants (kp and k,) in the radical polymerization of vinyl compounds have been reported so far. 1 These data were obtained primarily by the rotating sector method, non-stationary measurements (pre-effect or after-effect), the viscosity method, and the spatial interference method. The estimation of ·kp and k, from these indirect measurements is inevitably accompanied by large error. This explains the considerable scattering of data obtained by various authors. 1 Moreover, the data was obtained on the assumption that the rate of polymerization is described by the normal kinetic ESR spectroscopy is known to be possibly the best method for determining rate constants, since in principle stationary free radical concentration can be measured directly. Unfortunately, the stationary concentration of propagating radicals was too low to be detected by a commercial ESR spectrometer. Thus, ESR studies on propagating radicals were performed under special conditions such as the frozen state 2 • 3 and the crystalline state, 4 • 5 or by use of a special technique such as the flow technique. 6 -8 Since these conditions for measurement are quite different from those ordinarily used in radical polymerization, they are not applicable to the quantitative estimation of kinetic rate constants in radical polymerization.In 1972, Bresler et a/. 9 • 10 detected propagating radicals in the bulk polymerization system of vinyl compounds using a sensitive ESR spectrometer equipped with "a balance resonator," and estimated rate constants directly.We have observed more highly resolved ESR spectra than Bresler's for the propagating radicals of methacrylates in solution using an ESR spectrometer equipped with a specially designed TM 110 cavity. In the following, we report the ESR observation of the propagating radicals of methyl methacrylate (MMA) and its homologs in benzene at room temperature.The purification of MMA, 2 triphenylmethyl methacrylate (TPMA) 12 and benzene 11 has already been described. Benzyl methacrylate (BzMA), and isobutyl methacrylate (iBMAl were purified by the same method as MMA. 2 Benzoyl peroxide was repeatedly recrystallized from ethanol and dried in vacuo.

show abstract

ESR Study of the Propagating Radical in the Polymerization of MMA in Frozen State

Cited by 48 publications

References 31 publications

Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state

Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state

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

ESR Observation of Methacrylate Propagating Radicals in Stationary State

Contact Info

Product

Resources

About