Radical trapping and termination in free-radical polymerization of methyl methacrylate

Zhu, Shiping; Tian, Yuan; Hamielec, A. E.; Eaton, D. R.

doi:10.1021/ma00206a037

Cited by 174 publications

(148 citation statements)

References 10 publications

(14 reference statements)

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“…Similar spectra have been observed in pure irradiated MMA and PMMA [45][46][47]. The radiation induced reactions are similar, the main net reaction at 77 K being a hydrogen atom addition to the vinyl group.…”

Section: Methyl Methacrylate (Mma)supporting

confidence: 75%

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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

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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

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Section: Methyl Methacrylate (Mma)supporting

confidence: 75%

“…There might be two reasons for the observation of the 7-line spectrum at the same time. Firstly, the deuteration of the silica gel might not be complete and secondly H atoms can also be formed by the radiolysis of the monomer as indicated by the observation of the 7-line spectrum in irradiated pure MMA [45][46][47].…”

Section: Methyl Methacrylate (Mma)mentioning

confidence: 99%

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

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“…20,21 The incomplete functional groups are trapped in the form of residual monomers and unreacted pendent groups by reducing the diffusivity of the reactive species greatly as a result of the rapid gelation and vitrification during the light polymerization. Zhu et al 22 and Tial et al 23 reported that the lifetime of residual free radical at room temperature could reach several days or months, depending on cross-linking density and storage temperature. Marino et al 24 showed that the reaction of an irradiated unsaturated polyester specimen was observed for several days in the dark.…”

Section: Discussionmentioning

confidence: 99%

Dynamic Mechanical Properties of a Visible Light Curable Urethane Dimethacrylate Based Dental Resin

Lee

Kim

Lim

2003

Polym J

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ABSTRACT:The purpose of this study was to evaluate dynamic mechanical properties of urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) based dental resin. Dynamic mechanical properties of a visible light (λ = 400-500 nm) curable UDMA/TEGDMA (70:30 in wt%) resin were investigated for specimens uncured, light-cured for 40 s, and heated to 175• C subsequent to the irradiation for 40 s. Differential scanning calorimetry (DSC)was also employed as a complementary technique. For the light-cured specimen, two abrupt drops in the log storage modulus (E ) and two peaks in the tan δ vs. temperature curve corresponding to the glass transition were observed. The storage modulus was slightly increased with increasing temperature between the two modulus drops. The DSC experiment showed that the light-cured specimen contains residual living groups trapped by the fast reaction, which lead to further reaction during post-cure heat treatment. This further thermal reaction is considered to be responsible for the modulus increase. After heating to 175• C above the DSC exothermic peak, most of the residual groups in the light-cured specimen were found to be reacted, showing a single decrease in modulus and a single peak in the tan δ curve, and no exotherm in the DSC curve. With the aid of DSC data, the further thermal cure reaction with increasing temperature may occur within the glass transition region. The occurrence of the thermal reaction gives rise to the inaccuracy in determining the glass transition temperature (T g ). KEY WORDS Dynamic Mechanical Analysis (DMA) / DSC / UDMA / Storage Modulus / Tan δ / Glass Transition / It is well known that the dynamic mechanical analysis (DMA) is a very powerful technique for studying not only solid and viscoelastic liquids but also reactive materials undergoing changes in low molecular weight monomer to high molecular weight network. 1 The DMA technique is to impart the controlled mechanical oscillation to a solid or viscoelastic liquid, and to measure in-phase and out-of-phase response of the specimen. One calculates the storage modulus (E ) from the in-phase and the loss modulus (E ) from the out-of-phase response, which represent the energy stored and dissipated, respectively. Tan δ, where δ is the phase angle between the stress and strain in the oscillatory experiment, is given by the ratio of energy dissipated to energy stored per cycle (E /E ).From the analysis of the dynamic mechanical parameters, useful information on material properties can be obtained such as bulk properties directly related to material performance and primary and secondary transitions not easily identified by other methods. Typically, the information concerning polymeric systems from DMA includes quantitative modulus, glass transitions, rate and extent of polymerization, quantification of gelation, degree of cross-linking, and changes in polymer chain mobility. Among the dynamic mechanical properties in dental polymeric materials, the E as a parameter of materials stiffness and the gla...

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“…This is why microheterogeneity for a polymerizing system was not disputed even in works 2,7,10,15 which were observed to DCR conception. Quite the reverse, this factor is taken into account for explanation of the high concentration of radicals stored via polymerization proceeding at the expense of their trapping 6 by a solid polymeric matrix. In that work, where the peculiarities of polymerization at the high conversion can be explained by changing the chemical mechanism of chain termination, that is, by transition from a quadratic to a linear one, the latter also is considered as the physical elimination of active radicals, their transformation captured, "frozen," or "locked" by the solid polymeric matrix.…”

Section: Introductionmentioning

confidence: 99%

Kinetic model of block photopolymerization of glycidyl methacrylate to high conversion

Medvedevskikh

Bratus

Hafiychuk

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:The kinetics of glycidyl methacrylate block polymerization to high conversion was experimentally investigated with variations of the photoinitiator concentration, temperature, and power of UV illumination. The kinetic curves of this polymerization process contain three characterized sections of coordinates of "conversion-time," namely: The first one is practically linear to a conversion of Ϸ0.5, the second represents, by itself, the autoacceleration process, and the third presents the autodecelation process. An additional peculiarity of such a polymerization process is poor reproduction of the kinetic measurements. This reproduction does not correspond to instrumental error. Derivation of a kinetic model for block linear polymerization was done. This model is, quantitatively, in good agreement with all the data of the experimental material.

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Radical trapping and termination in free-radical polymerization of methyl methacrylate

Abstract: We have tried to simplify the nomenclature (see below) and used , and 2 for the three first-order parameters in the analysis of these molecules.

Cited by 174 publications

References 10 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

Dynamic Mechanical Properties of a Visible Light Curable Urethane Dimethacrylate Based Dental Resin

Kinetic model of block photopolymerization of glycidyl methacrylate to high conversion

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