Time-resolved EPR study of radicals from 2,2-dimethoxy-2-phenylacetophenone in ethylene glycol after flash photolysis

Konkin, A. A.; Roth, H.-K.; Schroedner, M.; Nazmutdinova, G. A.; Аганов, А. В.; Ida, Tetsuo; Garipov, Ruslan

doi:10.1016/s0301-0104(02)01025-x

Cited by 12 publications

(10 citation statements)

References 15 publications

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“…[19][20][21][22][23] However, the efficiency of DMPA for the polymerization of thick sections ($ 2 mm) has not received the same attention. In the photopolymerization of thick sections, as it is the case of light activated dental composites, the effect of the attenuation of the light intensity along the radiation path must be taken account.…”

Section: Resultsmentioning

confidence: 99%

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Mucci

Vallo

2011

J of Applied Polymer Sci

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The efficiency of 2,2-Dimethoxy-2-phenylacetophenone (DMPA) for the photopolymerization of methacrylate monomers in thick sections was assessed. DMPA is an efficient photoinitiator for thick sections (%2 mm) because a fast reaction and high conversions are obtained with concentrations as low as 0.25 wt % DMPA. The polymerization rate increased when the DMPA content increased from 0.125 wt % to 0.25 wt %. However, the conversion versus irradiation time profiles in resins containing 0.25 wt % or 0.5 wt % DMPA were similar. This is attributed to the screening effect caused by excessive levels of DMPA. In addition, the consumption of DMPA under UV irradiation was accompanied by the appearance of light absorbing photoproducts. Because the absorbing species nearest to the light source absorb part of it, the light fails to reach the deeper layers of the sample. The overall effect of light screening is a reduced photoinitiation rate and double bond conversion along the irradiation path. This effect was compensated by the use of irradiation sources of higher intensity; which increased the initiation rate by increasing the production of primary radicals. DMPA is colorless and it does not require the presence of amine as coinitiator. These properties make DMPA attractive as photoinitiator of dental composites.

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Section: Resultsmentioning

confidence: 99%

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Mucci

Vallo

2011

J of Applied Polymer Sci

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“…It was assumed that in ethylene glycol the following holds true: T 1 >> T 2 . This assumption allows the simplification of calculations and to obtain for 1,1-dimethoxybenzyl radical T 2 ¼ 0.8 ms. 36 In conclusion, it is worthwhile mentioning that a number of common PIs without an aromatic carbonyl group in their structure dissociate via an excited singlet state and demonstrate not an E/A but an A/E (absorptive/emissive) CIDEP pattern. An A/E CIDEP pattern was observed under photolysis of AIBN 17 and of HABI dimers 10,37 (see Fig.…”

Section: Cidep Under Photodissociation Of Initiatorsmentioning

confidence: 92%

“…35 The TR ESR spectrum of IRG651 in a viscous solvent ethylene glycol was subjected to a detailed analysis in Ref. 36. It was assumed that in ethylene glycol the following holds true: T 1 >> T 2 .…”

Section: Cidep Under Photodissociation Of Initiatorsmentioning

confidence: 99%

Laser Flash Photolysis of Photoinitiators: ESR, Optical, and IR Spectroscopy Detection of Transients

Khudyakov¹,

Turro

2009

Carbon‐Centered Free Radicals and Radical Cations

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“…It is worthwhile to consider in this case, what happens to the resonance line shape. Figure 2 shows TREPR spectra of geminate radical pairs (Scheme 1) resulting from photoinduced Norrish type-I cleavage (Nd-YAG, λ ¼ 355 nm) of 2,2-dimethoxy-1,2-diphenyl ethane-1-one (trade name: Irgacure ® 651) in aqueous SDS micellar solutions at room temperature [40,41]. The TREPR spectra in Figure 2 were acquired at the outlet of a microwave bridgewide bandwidth preamplifier (12 MHz gate), using a LeCroy digital oscilloscope at t obs ¼ 260 ns (A), ¼ 1.12 μs (B), and ¼ 3.6 μs (C)…”

Section: Features Of Trepr Spectroscopy: Spin-polarized "Free" Radicalsmentioning

confidence: 99%

Investigation of Liquid‐Phase Inhomogeneity on the Nanometer Scale Using Spin‐Polarized Paramagnetic Probes

Tarasov¹,

Forbes²

2017

Properties and Uses of Microemulsions

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The concept, basic physics, and experimental details of time-resolved electron paramagnetic resonance (TREPR) spectroscopy for the study of spin-correlated radical pairs (SCRPs) in heterogeneous media are presented and discussed. The delicate interplay between electron spin wave function evolution (governed by magnetic interactions such as the isotropic electron spin-spin exchange interaction and the electron-nuclear hyperfine interaction) and diffusion (governed by the size and microviscosity of the medium) provides a mechanism for assessing molecular mobility in confined spaces on the nanoscale (e.g., micelles, vesicles, and microemulsions). Experimental examples from micellar SCRPs are used to highlight the dominant features of the TREPR under different degrees of confinement and microviscosity, and spectral simulation methods are described to show how molecular mobility can be quantified.

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Time-resolved EPR study of radicals from 2,2-dimethoxy-2-phenylacetophenone in ethylene glycol after flash photolysis

Cited by 12 publications

References 15 publications

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Efficiency of 2,2‐dimethoxy‐2‐phenylacetophenone for the photopolymerization of methacrylate monomers in thick sections

Laser Flash Photolysis of Photoinitiators: ESR, Optical, and IR Spectroscopy Detection of Transients

Investigation of Liquid‐Phase Inhomogeneity on the Nanometer Scale Using Spin‐Polarized Paramagnetic Probes

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