Trifunctional Photoinitiators Based on a Triazine Skeleton for Visible Light Source and UV LED Induced Polymerizations

Abstract

Trifunctional photoinitiators (tPIs) based on benzophenone, anthracene, and pyrene chromophores linked to a triazine moiety are proposed as new initiating systems. In combination with an iodonium salt and a silane, these structures are able to initiate the radical polymerization RP of acrylates and the cationic polymerization CP of epoxides and vinylethers under Xe−Hg lamp, LED and very soft irradiation (i.e., halogen lamp). Upon addition of an amine, these new photoinitiators were also able to start the radical polymerization of acrylates. Excellent RP and CP polymerization profiles are obtained i.e. better than those recorded using the reference compounds (benzophenone, anthracence and pyrene). In CP, some of these compounds combined with thianthrenium salts can also be used. The mechanisms involved in the different multicomponent initiating systems were analyzed by ESR, fluorescence, steady state photolysis, and laser flash photolysis experiments.

Photochemical Production of Interpenetrating Polymer Networks; Simultaneous Initiation of Radical and Cationic Polymerization Reactions

“…The final coatings are tack-free. Such useful PIs in these novel dual photoinitiating systems are derived from dye structures and include e.g., diketopyrrolopyrrole-thiophene derivatives [107], mono and polyfunctional thiophene derivatives [108], indanedione skeleton [109], naphthalene scaffold [110], naphthalimide and naphthalic anhydride derivatives [111], anthraquinone derivatives [112], chalcone derivatives [113], push-pull malonate and malonitrile based compounds [114], naphthalimide based methacrylated derivatives [115], α-silicon polyoxomolybdate [116], acridinediones [117], difunctional acridinediones [118], Keggin-type polyoxometalate ion [119], push-pull structured indandiones [120], dimethyldihydropyrene [121], chromone based compounds [122], perylene bis-dicarboximides [123], pyrene derivatives [124], zinc complexes [125], pyridinium salts [126], pyrromethenes [127], trifunctional triazines [128], cyclometallated Pt(II) complexes [129], polyaromatic structures [130], and phenanthroline ligand containing Ru complex [131].…”

“…The high reactivity of the photoinitiating systems is exemplified by the fact that low viscosity formulations where oxygen inhibition is much more important can be used (e.g., acrylate (TMPTA)/epoxide (EPOX), acrylate (TMPTA)/divinylether (DVE), thiol (trimethylolpropane tris (3-mercaptopropionate) TMSH)/divinylether (DVE)). For example, the manufacture of IPN materials can be carried out under exposure to a large variety of wavelengths delivered by a Hg-Xe lamp (intensity ~40 mW/cm −2 ) [116,119,128,130] or laser diodes (intensity ~80 mW/cm −2 ) at 385-405 nm [110], 457 nm [108,111,[113][114][115]122,124], 473 nm [127], 473 nm (and likely 532, 635 nm) [120], 532 nm [107,123], 635 nm [112], from 473 up to 635 nm [121]. This was achieved under air (for EPOX/TMPTA blends) or in laminate (for EPOX/DVE blends as seen, e.g., in [124,125,127,128]).…”

Photopolymerization Reactions: On the Way to a Green and Sustainable Chemistry

“…The current efforts result in an amazing series of proposals of new PISs . For example, we have recently introduced PISs ( [99][100][101][102][103][104][105][106][107]) exhibiting really novel absorption properties (red-shift absorptions, multicolor absorptions, enhanced molar extinction coefficients, ε): e.g., colored substituted or functionalized ketones [60], modified organometallic derivatives [70][71][72][108][109][110][111][112][113][114][115][116][117] (ruthenium-, iridium-, platinum-, zirconium-and zinc-based complexes, titanocene derivatives…), various series of dye-based skeletons [61][62][63][65][66][67][68][74][75][76] (e.g., phenylenediamine, polystilbene, polyazine, violanthrone, acridinedione, 2,7-di-tert-butyldimethyldihydropyrene, bodipy, boranyl, thiophene, perylene bis-dicarboximide, hydrocarbons, pyrromethene, pyridinium salt…), di-and tri-functional architectures of photo initiators [64], light harvesting compounds [57,58] (where a strong molecular orbital coupling occurs, leading to ε huge values) and push-pull and multicolor photoinitiators (novel chromophores; donor--acceptor arrangements; unusual broad absorptions from the blue to the red wavelengths…).…”

“…Therefore, visible photons can be successfully used and Hg lamps avoided. The recent development of di-and tri-functional architectures of PIs, light harvesting PIs and push-pull and multicolor PIs opens a route towards highly absorbing PIs in the 400-800 nm range [57,58,64,73].…”

UV Curable Formulations for UV-C LEDs

“…Much interest was also focused on photoinitiators [2][3][4][5][6][7] and sensitizers [8] which are applicable to photocuring systems. On the other hand, there are a few reports on the application of UV-C LEDs, which emit lights below 300 nm, for sensors [9,10] and UV LED encapsulant [11].…”