Mechanistic studies of thioxanthone–carbazole as a one-component type II photoinitiator

Karaca, Nurcan; Balta, Demet Karaca; Öcal, Nüket; Arsu, Nergis

doi:10.1016/j.jlumin.2013.10.011

Cited by 43 publications

(25 citation statements)

References 16 publications

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“…Singlet oxygen then reacts with the anthracene moiety of TX-A to generate an endoperoxide intermediate. 84,[128][129][130] Due to the extended conjugation contributed by the incorporation of carbazole moieties, these photoinitiators exhibit strong absorption band in the visible region (> 400 nm) where both TX and carbazole chromophores have no significant absorption characteristics. Free radical polymerization of methacrylate and styrene based monomers were efficiently initiated using TX-A as onecomponent photoinitiator in the presence of oxygen.…”

Section: One-component Photoinitiationmentioning

confidence: 99%

Shining a light on an adaptable photoinitiator: advances in photopolymerizations initiated by thioxanthones

2015

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Photochemistry has been playing a central role in the synthetic polymer community. Aromatic ketones, examples of which include benzophenone, thioxanthone, camphorquinone, among others, are renowned for their excellent optical characteristics and have been extensively taken advantage of photochemically induction of polymerization processes. Of particular interest is thioxanthone due to its adaptability for bearing different functionalities and applications in various modes of photopolymerization which accomplishes photoinitiation in conjunction with other co-initiator compounds; a behavior that is referred to as bi-molecular photoinitiation. In this paper, we review the photochemistry of thioxanthonebased systems and their use in different modes of photoinitiated polymerizations. Citing examples from literature, the development of various photoinitiating systems based on thioxanthones along with an understanding of their mechanistic behavior has been elucidated in advance.Scheme 1 Typical representation of the photolysis of the radical photoinitiators based on Type I (top) and Type II (bottom) systems on the example of a benzoin derivative and thioxanthone, respectively.Scheme 3 Synthesis of thioxanthones by condensation of thiosalicylic acid and aromatic compounds in the presence of concentrated sulfuric acid.

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Section: One-component Photoinitiationmentioning

confidence: 99%

Shining a light on an adaptable photoinitiator: advances in photopolymerizations initiated by thioxanthones

2015

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“…Photopolymerization under visible light and low light intensity is an active research field still requiring the optimization of the chemical structures of photoinitiators [1][2][3][4][5][6][7][8][9][10][11][12]. With the aim of improving the polymerization efficiency, several parameters such as the light absorption properties (i.e., the molar extinction coefficient), the excited state lifetime, the redox properties and the energy levels, the photochemical stability or the easiness of synthesis have to be considered as the main parameters governing the reactivity [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Free Radical Photopolymerization and 3D Printing Using Newly Developed Dyes: Indane-1,3-Dione and 1H-Cyclopentanaphthalene-1,3-Dione Derivatives as Photoinitiators in Three-Component Systems

et al. 2020

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The design of photoinitiating systems with excellent photochemical reactivities at 405nm LED is one of the obstacles to efficiently promote free radical polymerization in mild conditions (e.g., low light intensity, under air). Here, our actual search for new multicomponent photoinitiating systems at 405nm LED prompts us to develop new dyes based on push–pull structures. In the present paper, we chose two series of new dyes which possess indane-1,3-dione and 1H-cyclopenta naphthalene-1,3-dione groups as the electron-withdrawing groups, since they have the great potential to behave as sensitive and remarkable photoinitiators in vat photopolymerization/3D printing. When incorporated with a tertiary amine (ethyl dimethylaminobenzoate EDB, used as electron/hydrogen donor) and an iodonium salt (used as electron acceptor) as the three-component photoinitiating systems (PISs), and among a series of 21 dyes, 10 of them could efficiently promote the free radical photopolymerization of acrylates. Interestingly, steady state photolysis experiments revealed different behaviors of the dyes. Fluorescence experiments and free energy change calculations for redox processes were also carried out to investigate the relevant chemical mechanisms. Additionally, the formation of radicals from the investigated PISs was clearly observed by electron spin resonance (ESR) spin-trapping experiments. Finally, stereoscopic 3D patterns were successfully fabricated by the laser writing technique. In this work, the use of push–pull dyes based on the naphthalene scaffold as photoinitiators of polymerization is reported for the first time in a systematic study aiming at investigating the structure–performance relationship for irradiation carried out at 405 nm. By carefully selecting the electron donors used in the two series of push–pull dyes, novel and high-performance photoinitiating systems operating at 405 nm are thus proposed.

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“…Type II are of the initiators hydrogen abstracted type and generally needs a hydrogen donor such as the amines and acids to produce initiating radicals. Among them thioxanthones are the most important Type II initiators . Recently, several thioxanthone derivatives which are mercapto water soluble panchromatic, polymeric, and visible photoinitiators were synthesized and their initiating efficiencies were reported.…”

Section: Introductionmentioning

confidence: 99%

Photochemically Prepared Gold/Polymer Nanocoatings: Formation of Gold Mirror

Çeper

Arsu

2017

Macro Chemistry & Physics

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In this study a rapid method is developed to obtain Au nanoparticles (AuNPs)/polymer composite materials by which HAuCl 4 salt is reduced and a polymer matrix is simultaneously generated by the means of UV light. 2-Mercaptothioxanthone (TX-SH), thioxanthone (TX), and TX + thiophenol are used as photoinitiator system for the poly(ethylene glycol) methyl ether acrylate and poly(ethylene glycol) diacrylate mixtures in the presence of HAuCl 4 . Except for a few studies, in situ reduction of Au ions, in an attempt to make them near or at polymer surface, has hardly been investigated at all. As a result of this study, it is important to note that the change of shape of NPs depends on the photoreducing species. TX-SH, due to thiol functionality in its structure, helps the production of the size, shape, and controlled distribution of AuNPs either in polymer matrix or in solution. Prepared AuNPs/polymer nanocoatings exhibit a reflected gold mirror view depending on the irradiation time. In addition to the foregoing approach in obtaining a thin film in the presence of AuNPs, it is expected that they are well ordered near the film surface with controlled shape and narrow range in size distribution.T. Çeper, Prof. N. Arsu Department of Chemistry Yildiz Technical University Davutpasa Campus Istanbul 34220, Turkey E-mail: narsu@yildiz.edu.tr the literature [6][7][8][9][10][11] but controlling size and shape as well as good distribution of NPs without agglomeration are still challenging areas for research. Most of the properties of NPs, such as catalytic, optical, etc., are clearly size dependent. [11,12] Usually photopolymerizable formulations consist of photoinitiators, oligomers, reactive diluents, and additives. Among these constituents, the photoinitiator plays an important role in the final properties of the cured coating as well as the oligomers and reactive diluents. Photoinitiators can be classed as cleavable and abstractable types. Cleavable initiators are called Type I and are less prone to oxygen inhibition. Type II are of the initiators hydrogen abstracted type and generally needs a hydrogen donor such as the amines and acids to produce initiating radicals. Among them thioxanthones are the most important Type II initiators. [13][14][15][16][17][18][19][20][21][22][23][24] Recently, several thioxanthone derivatives which are mercapto [13] water soluble [14,15,22] panchromatic, [24] polymeric, [14][15][16][17] and visible [18][19][20][21][22][23] photoinitiators were synthesized and their initiating efficiencies were reported.Type I and Type II initiators were used by several research groups for the preparation of Ag, Au, and

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Mechanistic studies of thioxanthone–carbazole as a one-component type II photoinitiator

Cited by 43 publications

References 16 publications

Shining a light on an adaptable photoinitiator: advances in photopolymerizations initiated by thioxanthones

Shining a light on an adaptable photoinitiator: advances in photopolymerizations initiated by thioxanthones

Free Radical Photopolymerization and 3D Printing Using Newly Developed Dyes: Indane-1,3-Dione and 1H-Cyclopentanaphthalene-1,3-Dione Derivatives as Photoinitiators in Three-Component Systems

Photochemically Prepared Gold/Polymer Nanocoatings: Formation of Gold Mirror

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