Photochemistry and photopolymerization study on 2-acetoxy and methyl-2-acetoxy derivatives of thioxanthone as photoinitiators

Catalina, F.; Tercero, J.M.; Peinado, C.; Sastre, R.; Mateo, J. L.; Allen, Norman S.

doi:10.1016/1010-6030(89)85019-1

Cited by 49 publications

(31 citation statements)

References 14 publications

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“…8,15 The absorption spectra of TX-Ct and TX-Ma are shown in Figure 1. TX-Ct possesses absorption characteristics similar to the monofunctional TX-Ma and the parent thioxanthone ( Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Studies of Photoinitiated Free Radical Polymerization Using a Bifunctional Thioxanthone Acetic Acid Derivative as Photoinitiator

et al. 2009

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A bifunctional photoinitiator for free radical polymerization, thioxanthone catechol-O,O 0 -diacetic acid, was synthesized, characterized, and compared to photoinitiator parameters of the monofunctional analogue, 2-(carboxymethoxy)thioxanthone. Photophysical studies such as fluorescence, phosphorescence, and laser flash photolysis in addition to photopolymerizations of methyl methacrylate show that the bifunctional photoinitiator is more efficient in polymer generation than the monofunctional derivative. These studies suggest that initiator radicals are generated from a π-π* triplet state in an intramolecular electron transfer, followed by proton transfer and decarboxylation to generate alkyl radicals, which initiate polymerization. The initial electron transfer is faster for the bifunctional photoinitiator than the monofunctional derivative, which is based on laser flash photolysis studies. Because of the relatively fast intramolecular radical generation from the triplet state (triplet lifetime = 490 ns), quenching by molecular oxygen is insignificant and polymerization of methyl methacrylate proceeds efficiently without deoxygenation. At higher concentrations of initiator (∼5 mM) intermolecular electron transfer competes with intramolecular electron transfer. Both processes, inter-and intramolecular processes, yield initiating alkyl radicals.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Studies of Photoinitiated Free Radical Polymerization Using a Bifunctional Thioxanthone Acetic Acid Derivative as Photoinitiator

et al. 2009

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“…The compounds 2-thioxanthone-thioacetic acid (TX-SCH 2 COOH) and 2-(carboxymethoxy)thioxanthone (TX-OCH 2 COOH) were synthesized by the modified literature [13] procedure described for the synthesis of 2-hydroxythioxanthone according to Scheme 3.…”

Section: Resultsmentioning

confidence: 99%

One‐Component Bimolecular Photoinitiating Systems, 2

Aydın

Arsu

Yaǧcı

2003

Macromol. Rapid Commun.

178

127

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The compounds 2‐thioxanthone‐thioacetic acid and 2‐(carboxymethoxy)thioxanthone, bimolecular photoinitiators for free radical polymerization, are synthesized and characterized. Their capability to act as initiators for the polymerization of methyl methacrylate was examined. The postulated mechanism is based on the intermolecular electron‐transfer reaction of the excited photoinitiator with the sulfur or oxygen atom of the ground state of the respective photoinitiator followed by decarboxylation. The resulting alkyl radicals initiate the polymerization.Structures of the photoinitiators.magnified imageStructures of the photoinitiators.

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“…The alkylamino radical is the effective initiator of polymerization. 15 In this work the triplet reactivity of TX towards hydrogen and electron donors was investigated employing the laser flash photolysis technique (LFP). Vol.…”

Section: Introductionmentioning

confidence: 99%

Laser flash photolysis study of the photochemistry of thioxanthone in organic solvents

Rodrigues¹,

Silva²,

Netto‐Ferreira³

2010

J. Braz. Chem. Soc.

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A fotorreatividade do estado excitado triplete de tioxantona (TX) foi investigada empregando a técnica de fotólise por pulso de laser. O máximo do comprimento de onda de absorção e o tempo de vida para o seu estado excitado triplete são dependetes do solvente. Quando foram utilizados solventes doadores de hidrogênio, foi observado o surgimento de uma nova banda no espectro de absorção para os transientes, com máximo a 410 nm, a qual foi atribuída ao radical cetila derivado da tioxantona. As constantes de velocidade de supressão para o triplete de tioxantona, k q , variaram de (1,7 ± 0,1) × 10 6 L mol -1 s -1 para tolueno a ca. 10 9 L mol -1 s -1 para fenol e seus derivados contendo substituintes poleres, bem como para indol, trietilamina e DABCO.The photoreactivity of the triplet excited state of thioxanthone (TX) was investigated employing the laser flash photolysis technique. The wavelength for the absorption maximum and the lifetime of the triplet excited state are solvent dependent. When hydrogen donor solvents were employed, a new band at 410 nm was observed in the triplet absorption spectrum, which was attributed to the ketyl radical derived from thioxantone. Quenching rate constants, k q , ranged from (1.7 ± 0.1) × 10 6 L mol -1 s -1 for toluene to ca. 10 9 L mol -1 s -1 for phenol and its derivatives containing polar substituents, as well as for indole, triethylamine and DABCO.

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Photochemistry and photopolymerization study on 2-acetoxy and methyl-2-acetoxy derivatives of thioxanthone as photoinitiators

Cited by 49 publications

References 14 publications

Mechanistic Studies of Photoinitiated Free Radical Polymerization Using a Bifunctional Thioxanthone Acetic Acid Derivative as Photoinitiator

Mechanistic Studies of Photoinitiated Free Radical Polymerization Using a Bifunctional Thioxanthone Acetic Acid Derivative as Photoinitiator

One‐Component Bimolecular Photoinitiating Systems, 2

Laser flash photolysis study of the photochemistry of thioxanthone in organic solvents

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