Photoinitiators and photoinitiation, 3. Comparison of the photodecompositions of α‐methoxy‐ and α,α‐dimethoxydeoxybenzoin in 1,1‐diphenylethylene as model substrate

Groenenbook, Cornelis J.; Hageman, Hendrik J.; Overeem, Ton; Weber, Anton

doi:10.1002/macp.1982.021830202

Cited by 73 publications

(24 citation statements)

References 20 publications

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“…[50] When dividing the cell in five parts, we assume that there is no mixing between the different parts by diffusion. This assumption has been checked using the second Fick's law:…”

Section: Calculation Of the Concentration Of Radicals Produced Per Pumentioning

confidence: 99%

Pulsed Laser Polymerization of Alkyl Acrylates: Potential Effects of the Oxygen Presence and High Laser Power

Castignolles

Nikitin

Couvreur

et al. 2005

Macro Chemistry & Physics

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Summary: Unexpected difficulties are encountered in the determination of propagation rate coefficients (kp) in free radical polymerization of alkyl acrylates by pulsed laser polymerization (PLP), mainly due to intramolecular transfer to polymer.1 This article is focused on the role played by the high laser power in these difficulties and the possible reactions of mid‐chain radical with residual oxygen. Removing the oxygen by simple bubbling of nitrogen is sufficient to avoid alteration of the polymerization kinetics of acrylates by residual oxygen under PLP conditions. Moreover, no degradation of polymer (or solvent) has been detected after irradiation with the high laser power typically used in PLP experiments. However, it has been shown that this high laser power completely prevents from having a temporally and spatially homogeneous radical concentration in the PLP cell. A model is proposed here to simulate the pulsed laser polymerization taking initiator consumption and laser energy absorption into account. According to our simulation results, this non‐negligible initiator consumption and laser power absorption can indeed have a positive influence, i.e., it favors the obtainment of a bimodal molar mass distribution fulfilling the IUPAC consistency criteria. This observation may contradict the idea that PLP‐SEC is not suitable to determine accurate kp values for acrylates above 20–30 °C.

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“…[50] When dividing the cell in five parts, we assume that there is no mixing between the different parts by diffusion. This assumption has been checked using the second Fick's law:…”

Section: Calculation Of the Concentration Of Radicals Produced Per Pumentioning

confidence: 99%

Pulsed Laser Polymerization of Alkyl Acrylates: Potential Effects of the Oxygen Presence and High Laser Power

Castignolles

Nikitin

Couvreur

et al. 2005

Macro Chemistry & Physics

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“…Explanation can be given by the instability of the ketal-like products. The non-polymerizable double bond containing compounds DPE and DTE have been described by Hageman et al [5,6] These model substrates for vinyl monomers represent styrene rather than acrylic esters, which are mostly used as reactive components in radiation curing. Another disadvantage of DPE and DTE is their low triplet energy (E T(DPE) % 247 kJ mol À1 ), which enables them to quench the triplet states of most PIs.…”

Section: Full Papermentioning

confidence: 99%

“…[4] Alternatively, the radicals could be quenched with stable radicals or non-polymerizable double bond to create stable products, which could be analyzed with analytical routine methods like NMR, IR, or MS. Different quenchers such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), [5] 1,1-diphenylethene (DPE), 1,1-di(p-tolyl)ethene (DTE), [6,7] and methyl 3,3-dimethyl-2-methylenebutanoate t-BAM [8,9] (Figure 1) have been described. TEMPO, a commercially available stable radical, reacts efficiently with carbonyl radicals originating from, e.g., cleavable hydroxy-or aminoalkylphenones.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Investigations on a Diynone Type Photoinitiator

Seidl

Liska

2007

Macro Chemistry & Physics

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Recently, it has been shown that 1,5‐diphenyl‐penta‐1,4‐diyn‐3‐one (DPD) has some surprising characteristics as photoinitiator for free radical polymerization. In the present investigations we focused on the photochemistry in hydrogen donating isopropyl alcohol (IPA) and neutral acetonitrile (MeCN). HPLC and column chromatographic separation were applied for photoproduct identification. Different types of radical quenchers such as the stable radical TEMPO and the non‐polymerizable monomer methyl t‐butacrylate (t‐BAM) were also used to identify the initiating species. In IPA, fast hydrogen abstraction reaction similar to that of benzophenone was found, whereas the hydrogen donor is the initiating molecule. Significantly, slower 2 + 2 cycloaddition reaction involving the carbonyl group is the predominant pathway in MeCN. Experiments with t‐BAM indicated that DPD is directly responsible for the initiation process.magnified image

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“…From the reported data, it is possible to evaluate the polymerization quantum yield 4Sp (number of molecules polymerized per photon absorbed) and the kinetic chain length of the cross-linking polymerization, simply by taking the ratio of 4Sp to the initiation quantum yield ((Di ^-0.4) [22]. The photocuring of these acrylic resins was found to proceed with long kinetic chains, each initiating radical being capable of inducing the polymerization of up to 20 000 acrylate double bonds.…”

Section: Uv-sensitive Liquid Photopolymersmentioning

confidence: 99%

Laser-induced curing of functional polymers

Decker

1998

Designed Monomers and Polymers

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Abstraet-Telechelic oligomers and polymers have been cross-linked within milliseconds upon exposure to a UV laser beam in the presence of a photoinitiator. The polymerization reaction was followed in real-time by infrared spectroscopy and was shown to proceed with long kinetic chains (up to 20000 functional groups polymerized per initiating radical). Acrylate-functionalized polyesters proved to be the most reactive systems, with the formation of tightly cross-linked and strictly insoluble polymers. Their high sensitivity (0.1 mjcm-2) makes these photoresists particularly well suited for laser direct imaging applications, with writing speeds up to 1000 ms-1. The rate at which polymer chains grow in media undergoing cross-linking polymerization was determined from pulsed laser experiments. Similar results have been obtained with epoxy-and vinyl ether-functionalized polymers, which undergo a fast cationic polymerization in the presence of a photogenerated protonic acid. Interpenetrating polymer networks have been synthesized by laser irradiation of blends of acrylate-and epoxy-functionalized oligomers. These polymers combine the elastomeric character of cross-linked polyurethanes and the toughness of epoxy polymers. The two networks can be produced either simultaneously by irradiation at 325 nm (helium-cadmium laser), or one after the other upon two successive UV exposures, by acting on the wavelength of the laser emission and on the type of radical and cationic photoinitiators. These lasersensitive polymers can be used as photoresists to produce microcircuits, as protective coatings of optical fibers, as recording media in holography, and as optical guides in photonic applications.

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Photoinitiators and photoinitiation, 3. Comparison of the photodecompositions of α‐methoxy‐ and α,α‐dimethoxydeoxybenzoin in 1,1‐diphenylethylene as model substrate

Cited by 73 publications

References 20 publications

Pulsed Laser Polymerization of Alkyl Acrylates: Potential Effects of the Oxygen Presence and High Laser Power

Pulsed Laser Polymerization of Alkyl Acrylates: Potential Effects of the Oxygen Presence and High Laser Power

Mechanistic Investigations on a Diynone Type Photoinitiator

Laser-induced curing of functional polymers

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