Silyl glyoxylates are proposed here as a new class of high performance type I photoinitiators for free radical polymerization under air or in laminate (e.g., (meth)­acrylates) upon exposure to different near-UV (at 395 nm; at 405 nm) and blue (at 477 nm) LEDs. The new proposed photoinitiators can also be used in the presence of additives that can enhance their initiating ability: an iodonium salt and an amine or a phosphine. The silyl glyoxylate-based photoinitiating systems exhibit excellent polymerization performances upon blue LED light (at 477 nm) with exceptional bleaching properties compared to camphorquinone (CQ)-based systems. This can be highly worthwhile for the preparation of colorless polymers upon visible light. Real-time Fourier transform infrared spectroscopy (RT-FTIR) experiments are used to monitor the polymerization profiles. The involved chemical mechanisms are investigated by fluorescence, laser flash photolysis, electron spin resonance (ESR), and steady state photolysis experiments. Molecular orbital calculations are also carried out. The overall excited state processes and the chemical mechanisms involved in the initiation step are detailed.

Diaryliodonium salts are well-established compounds in free radical chemistry and are already used as photoinitiators (free radical or cationic polymerization), but the presence of counter anions is a strong drawback. Indeed, a counter anion is always required (e.g., SbF6−) leading to potential toxicity issues or release of HF. In the present paper, counter anion-free and fluoride-free aryliodonium salts are proposed, that is, aryliodonium ylides (AY) are studied here as new and efficient additives for radical chemistry and an example is provided for the camphorquinone (CQ)/amine based photoinitiating systems (PISs) for the polymerization of thick (1.4 mm) and thin (20–13 µm) methacrylates under air and blue light irradiation. The newly proposed PISs, for example, CQ/amine/AY, presented excellent polymerization performances and good bleaching properties were obtained after polymerization. Real-time Fourier transform infrared spectroscopy (RT-FTIR) was used to monitor the photopolymerization profiles. The chemical mechanisms involved were investigated using electron spin resonance (ESR).

Iodonium sulfonates are proposed here as a new class of high‐performance coinitiators for camphorquinone (CQ)‐based systems for the polymerization of methacrylates under blue light irradiation. When combined with CQ, the new proposed coinitiators present excellent polymerization performances and are excellent candidates for the replacement of tertiary aromatic amines subjected to toxicological concerns in the well‐established CQ/amine photoinitiating system (PIS). Remarkably, good bleaching properties are obtained after polymerization. The use of the new PIS for dental adhesives is also investigated. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1664–1669

well-known alkyl phenylglyoxylates (APG) due to the introduction of a (trialkylsilyl) moiety. [15] The alkyl(trialkylsilyl)glyoxylates are high performance PIs efficient under visible light exposure and especially blue light irradiation. Based on molecular orbital calculations, the objective of this article is to replace the alkoxy group of the ester function of the alkyl(trialkylsilyl)glyoxylate by an aryl group to form 1-aryl-2-(triisopropylsilyl)ethane-1,2-diones (SEDs, Scheme 1). These compounds should present a bathochromic shift of the absorption properties of the PIs. To the best of our knowledge, SEDs were never reported in the literature as visible light photoinitiators. The reactivity of SEDs is determined as PIs for the free radical polymerization of a urethane dimethacrylate (UDMA-Scheme 2) upon exposure to blue and green LEDs. Their bleaching properties are particularly worthwhile, that is, better than titanocene or CQ/ amine systems (Scheme 2).The SEDs, 1-phenyl-2-(triisopropylsilyl)ethane-1,2-dione (SED1) and 1-(3,4,5-trimethoxyphenyl)-2-(triisopropylsilyl)ethane-1,2-dione (SED2), were prepared in two steps (Scheme 1, Supporting Information): 1) Pd-catalyzed Sonogashira cross-coupling between an aryl iodide and (triisopropylsilyl)acetylene in the presence of CuI, diisopropylamine in MeCN leading almost quantitatively to the desired alkynes 1a and 1b; [16] 2) oxidation of the triple bond using RuO 2 , NaIO 4 in a mixture of CCl 4 /MeCN/H 2 O giving SED1 and SED2. [17] It is noteworthy that step 2 proceeds in low yield due to a partial degradation of 1a and 1b under the oxidation conditions. However, before Photoinitiators 1-Aryl-2-(triisopropylsilyl)ethane-1,2-diones (SEDs) are proposed here as a new class of visible Type I photoinitiators (PIs) for free radical polymerization under air upon exposure to blue (@455 nm) and green (@520 nm) LEDs. Remarkably, these new systems present good polymerization performances and excellent bleaching properties compared to camphorquinone-based systems, and transparent polymers are obtained upon visible light irradiation. Real-time Fourier transform infrared spectroscopy is used to monitor the polymerization profiles. Molecular orbital calculations are also carried out for a better understanding of the structure/reactivity relationship of the photoinitiators.Photopolymerization techniques have been widely studied and used over the past decades. Due to several advantages compared to thermal polymerization methods, photopolymerization has many industrial applications such as coatings, inks, adhesives, photolithography, 3D printing, and dentistry. [1,2] Nevertheless, the majority of the commercially available photoinitiators is UV sensitive. [3,4] However, visible emitting light sources such as LEDs are of great interest due to their lower price, lower energy consumption, and safer operating conditions. The use of these irradiation sources requires the development of new photoinitiating systems (PISs) absorbing in the visible spectral range, typically in the 400-500 ...

2‐Oxo‐2‐(tert‐butyldimethylsilyl)acetic acid (DKSi‐COOH), is proposed here as a new high‐performance photoinitiator (PI) for the free radical polymerization of methacrylates under blue light irradiation. In the presence of DKSi‐COOH, very good polymerization performances are reached and outstanding bleaching properties are obtained compared to traditionally used camphorquinone‐based photoinitiating systems. Remarkably, this new developed PI exhibits good water solubility and excellent stability in acidic conditions and represents therefore a promising candidate for water‐based formulations.

Silyl glyoxylates are proposed here as high‐performance photoinitiators (PIs) for the hybrid polymerization of cationic and radical monomers. Recently, silyl glyoxylates were reported as a new class of high‐performance Type I photoinitiators for free radical polymerization under air upon exposure to different near‐UV and blue LEDs. In this article, we report this new class of photoinitiators to initiate cationic polymerization in combination with an iodonium salt. This system can also be used to initiate simultaneously free radical and cationic polymerizations, for example, for the free radical/cationic hybrid polymerization and for the synthesis of interpenetrating polymer networks. The system silyl glyoxylate/iodonium exhibits excellent polymerization performances and exceptional bleaching properties compared to other well established photoinitiators (e.g., camphorquinone). Furthermore, a hybrid monomer is also introduced in this article (2‐vinyloxyethoxyethyl methacrylate [VEEM]) leading to a huge improvement of the mechanical properties of the final polymer through hybrid polymerization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1420–1429

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as observed for other triarylphosphines in ref. [5]. The polymerization under air of composites is a huge challenge and the development of photoinitiating systems able to work in such mild conditions (visible light, aerated conditions) is highly desired. [6][7][8][9] It will be the aim of our paper.Based on our recent work on iodonium sulfonates, [10] we propose here a new phosphine with a sulfonate group on its structure and potentially combined with an iodonium salt (Scheme 1) as efficient coinitiator for CQ-based photoinitiating systems for the polymerization upon visible light. The aim of this study is to enhance the DoC of composites obtained by photopolymerization.