A thioxanthone‐based visible photoinitiator

Abstract

Thioxanthone‐based 9‐(2‐Morpholine‐4yl‐acetyl)‐5‐thia‐napthasen‐12‐one (TX‐MPM) was synthesized and characterized as a one‐component novel visible photoinitiator. Its capability to act as an initiator for the polymerization of methyl methacrylate (MMA) was examined in photoreactor and also daylight. Photophysical properties: fluorescence and phosphorescence emission spectra and fluorescence quantum yield of TX‐MPM (ϕf = 0.29) were determined. The phosphorescence lifetime was found 131 ms for TX‐MPM and 110 ms for initiator‐attached polymer (PMMA) at 77 K, indicated a π→π* nature of the lowest triplet state. A model compound, morpholino acetonapthone was used as quencher for the triplet states of TX‐MPM and the quenching rate constant was determined (kq = 1.26 × 109 M−1s−1). According to laser flash photolysis studies, intermolecular hydrogen abstraction process was more dominant path to the formation of the initiating radicals. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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

“…The proposed mechanism of the photoinitiation relies on the photoexcitation of TX-A photoinitiator and quenching the triplet excited state primarily by molecular oxygen to form singlet oxygen species. [125][126][127] Carbazole functionalities were also taken advantage of forming one-component TX photoinitiators with extended conjugation. The endoperoxide thus formed undergoes photochemical or thermal decomposition resulting in the formation of initiating radicals.…”

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

“…Versatile Photopolymerization under Visible LEDs FRP of Acrylates TX and its derivatives, for example, ITX, are often used to initiate FRP combined with additives, for example, tertiary amine. [32][33][34][35][36][37] In this study, MDEA was selected as the additive to compare the efficiency of PI/MDEA PIS, and TPGDA was used as the monomer. The ITX/MDEA, ITX-P/MDEA, or ITX-S/MDEA PIS can initiate the FRP of TPGDA in the laminate under LED irradiation ( Fig.…”

“…These new derivatives exhibit excellent light absorption properties and they can efficiently initiate various photopolymerizations Additional Supporting Information may be found in the online version of this article. when modified with different substitutions, [32][33][34][35][36][37] such as TXfluorenes and TX-carbazole derivatives. 32,33 In this study, we designed and developed two novel ITX derivatives, namely, 2-isopropyl-7-(3-(methylthio)phenyl)-9Hthioxanthen-9-one (ITX-P) and (E)-2-(3-(methylthio)styryl)-7isopropyl-9H-thioxanthen-9-one (ITX-S), as shown in Scheme 1.…”

Preparation of Single Chain Nanoparticles via Photoinduced Double Collapse Process

“…Photoinduced radical polymerization technique has been used in extensive applications such as curing of polymeric coatings, polymers with controlled molecular weight, linear and branched copolymers, and preparation of nanoparticles. Free radical photoinitiators are divided into two particular subgroups: i) Type I that is subjected to direct cleavage and widely used in various photoapplications and ii) Type II, which has longer wavelength absorption characteristics compared to Type I photoinitiators . Benzophenone is a conventional Type II initiator and used in various UV‐curing applications such as microelectronics, production of 3D objects, coatings, etc .…”

“…Free radical photoinitiators are divided into two particular subgroups: i) Type I that is subjected to direct cleavage and widely used in various photoapplications [29,30] and ii) Type II, which has longer wavelength absorption characteristics compared to Type I photoinitiators. [31,32] Benzophenone is a conventional Type II initiator and used in various UV-curing applications such as microelectronics, production of 3D objects, coatings, etc. [32,33] Benzophenone and its derivatives act as a Type II initiators and require an external compound (coinitiator/hydrogen donor) to initiate the photopolymerization.…”