One/two-photon cationic polymerization in visible and near infrared ranges using two-branched sulfonium salts as efficient photoacid generators

et al. 2018

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Three novel types of thiophene‐containing oxime sulfonates with a big π‐conjugated system were reported as non‐ionic photoacid generators. The irradiation of the newly synthesized photoacid generators using near UV–visible light‐emitting diodes (LEDs) (365–475 nm) results in the cleavage of two weak NO bonds in single molecules, which lead to the generation of different sulfonic acids in good quantum and chemical yields. The mechanism for the NO bond cleavage for acid generation was supported by the UV–visible spectra and real‐time 1H NMR spectra. They are developed as high‐performance photoinitiators without any additives for the cationic polymerization of epoxide and vinyl ether upon exposure to near‐UV and visible LEDs (365–475 nm) at low concentration. In the field of photopolymerization, especially visible light polymerization, it has great potential for application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 776–782

Section: Methodsmentioning

confidence: 99%

Bis‐substituted thiophene‐containing oxime sulfonates photoacid generators for cationic polymerization under UV–visible LED irradiation

Sun

et al. 2018

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“…The photolysis rates were maintained sufficiently small so that the changes of A λ were lower than 10%. Rhodamine B (RhB) was used as a sensor of photoacid generation . The acid generation in acetonitrile was also evaluated from a calibration curve of RhB, which was gradually protonated by the addition of p ‐toluenesulfonic acid.…”

Section: Methodsmentioning

confidence: 99%

“…Now, the commercial PAGs exhibit weak spectral sensitivity at long wavelengths ( λ abs > 320 nm), which limit their applications of new light sources, for example, light‐emitting diodes (LEDs) . PAGs have been adapted to operate under LED irradiation, especially near‐UV/visible LEDs . These eco‐friendly light sources have the advantages of low cost, absence of harmful ultraviolet light, high efficiency, and so on …”

Section: Introductionmentioning

confidence: 99%

D‐π‐a‐type oxime sulfonate photoacid generators for cationic polymerization under UV–visible LED irradiation

Zhou

et al. 2018

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Four D-p-A-type nonionic oxime sulfonate photoacid generators (PAGs) have been designed and synthesized for use in light-emitting diode (LED) excitable cationic photoinitiators, in which N,N-diphenylamino was used as electron donor with trifluoroacetophenone-based oxime sulfonates (trifluoromethanoesulfonate and p-toluenesulfonate) as electron acceptor and substituted fluorene and biphenyl groups as the p-conjugated systems. PAG-Ben-Tol (with biphenyl and p-toluenesulfonate) and PAG-Flu-Tol (with fluorene and p-toluenesulfonate) showed high quantum yields of photoacid generation (0.33-0.50) and very good thermal stability (over 250 8C). The absorbance spectra of these PAGs were consistent with the emission spectra of commercially gained UV-visible LED light sources.The potential of these PAGs for cationic photoinitiators was tested in two cationic monomer systems. These PAGs needed low light intensity and low concentration for photopolymerization with high conversions of monomer, for example, over 80%, gained at 3.0 mW cm 22 from 365 to 470 nm LEDs. The photochemical mechanisms of these PAGs are comprehensively investigated and discussed in detail.

“…Hence, the design and development of PIs or PISs for versatile polymerizations under LEDs irradiation have attracted attention in recent years . Many PIs and PISs exhibiting excellent light‐sensitive properties to LEDs have also been proposed . Lalevee et al developed zinc tetraphenylporphyrin as a high performance visible light photoinitiator, which could efficiently initiate FRP and CP.…”

Section: Introductionmentioning

confidence: 99%

“…Liu et al synthesized novel photoinitiators contained TX, which realized simultaneous thiol‐yne‐epoxy hybrid photopolymerization. The reactive species (i.e., cations and free radicals) produced from the PIs or PISs based on different chromophores themselves or combined with an iodonium salt (Iod), N ‐vinylcarbazole, or an amine are highly efficient for versatile photopolymerizations (FRP, CP, hybrid, and TEP) upon LED irradiation (365–450 nm) …”

Section: Introductionmentioning

confidence: 99%

Visible light‐emitting diode‐sensitive thioxanthone derivatives used in versatile photoinitiating systems for photopolymerizations

Malval

et al. 2017

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Novel thioxanthone (TX) derivatives are used as versatile photoinitiators upon visible light-emitting diode (LED; e.g., 405, 425, and 450 nm) exposure. The mechanisms for the photochemical generation of reactive species (i.e., cations and free radicals) produced from photoinitiating systems based on the photoinitiator and an iodonium salt, tris(trimethylsilyl)silane, or an amine, were studied by UV-vis spectroscopy, fluorescence, cyclic voltammetry, steady-state photolysis, and electron spin resonance spin-trapping techniques. The reactive species are particularly efficient for cationic, free radical, hybrid, and thiol-ene photopolymerizations upon LED exposure. The optimized photoinitiating systems exhibit higher efficiency than those of reference systems (i.e., isopropyl TXbased photoinitiating systems), especially in the visible range. According to their beneficial features, these photoinitiating systems have considerable potential in photocuring applications.