Disubstituted Aminoanthraquinone-Based Multicolor Photoinitiators: Photoinitiation Mechanism and Ability of Cationic Polymerization under Blue, Green, Yellow, and Red LEDs

The investigation and clarification of the photoinitiation mechanism of novel systems are of importance for the design and development of compounds with high photoinitiation efficiency of photopolymerization. Some disubstituted aminoanthraquinone derivatives have been reported to exhibit interesting photochemical/photophysical properties and have the potential to act as high performance multicolor photoinitiators under the irradiation of various wavelengths of visible light from light-emitting diodes (LEDs). Herein, three disubstituted aminoanthraquinone derivatives, i.e., 1-amino-4-hydroxyanthraquinone, 1,4-diaminoanthraquinone, and 1,5-diaminoanthraquinone, with iodonium salt and N-vinylcarbazole as additives, have been investigated. Their photoinitiation mechanism was studied using fluorescence spectroscopy, laser flash photolysis, steady state photolysis, computational quantum chemistry, and electron spin resonance spin trapping techniques. Then, their photoinitiation ability for the cationic photopolymerization of epoxide and divinyl ether monomers under the irradiation of diverse LEDs (i.e., blue, green, yellow, and red LEDs) was investigated. The types and positions of substituents were found to play a vital role in the photoreactivity and photoinitiation ability of the disubstituted aminoanthraquinone derivative-based photoinitiating systems.P.X. acknowledges funding from the Australian Research Council Future Fellowship (FT170100301). M.L.C. gratefully acknowledges a Georgina Sweet ARC Laureate Fellowship (FL170100041) and generous allocations of supercomputing time on the National Facility of the Australian National Computational Infrastructur

Recent Developments of Versatile Photoinitiating Systems for Cationic Ring Opening Polymerization Operating at Any Wavelengths and under Low Light Intensity Sources

Photoinitiators (PI) or photoinitiating systems (PIS) usable in light induced cationic polymerization (CP) and free radical promoted cationic polymerization (FRPCP) reactions (more specifically for cationic ring opening polymerization (ROP)) together with the involved mechanisms are briefly reviewed. The recent developments of novel two- and three-component PISs for CP and FRPCP upon exposure to low intensity blue to red lights is emphasized in details. Examples of such reactions under various experimental conditions are provided

Recent Applications of the (TMS)3SiH Radical-Based Reagent

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

In this paper, we propose to review the ways to produce, through photopolymerization, interpenetrating polymer networks (IPN) based, e.g., on acrylate/epoxide or acrylate/vinylether blends and to outline the recent developments that allows a one-step procedure (concomitant radical/cationic polymerization), under air or in laminate, under various irradiation conditions (UV/visible/near IR; high/low intensity sources; monochromatic/polychromatic sources; household lamps/laser diodes/Light Emitting Diodes (LEDs)). The paper illustrates the encountered mechanisms and the polymerization profiles. A short survey on the available monomer systems and some brief examples of the attained final properties of the IPNs is also provided

Photothermal activation in the near infrared range for 4-dimensional printing using relevant organic dyes

International audience4D printing has become an exciting sector of 3D printing since its appearance in the 2010s. This technology consists in adding time as an extra dimension of 3D printing. Different stimuli can be used to modify a 3D object after the printing process such as solvent, temperature, magnetic field, electricity or light. In this paper, a 4D behaviour was investigated using NIR light in combination with a low amount of NIR organic dyes in-situ embedded in the 3D printed polymer. As a first step, the influence of several parameters on the photothermal effect generated have been followed such as the NIR dye structure, the NIR dye concentration, the irradiation wavelength, the light irradiance and the polymer matrix. Due to the light-triggered process, the deformation of the 3D printed object could be reversibly achieved in the presence of a NIR organic dye in a few amount of time (20 s). In fact, the photothermal effect in-situ generated in the 3D printed object allowed to reach a temperature above the Tg of the latter. This phenomenon has been highlighted with tensile tests. Indeed, these tests showed the passage of the 3D printed object from a glassy state to a rubbery state upon NIR irradiation. Finally, the photothermal effect produced was used to rapidly bond two parts of a broken 3D printed object

Near‐infrared light for polymer re‐shaping and re‐processing applications

International audienceThe shaping and reprocessing of polymers are usually associated with strong energetic costs, strongly limiting their practical usage. In this paper, a new approach is proposed based on a NIR activation of the material in presence of a NIR heater for a highly efficient process upon ecofriendly NIR light emitting diodes irradiation. Markedly, due to this light-triggered process, a spatial control of the shaping/reprocessing behavior can be obtained i.e. only the needed parts are irradiated preventing a heating of all the sample. In this work, different thermoplastics are reshaped or reprocessed due to NIR activation in presence of an organic NIR dye used as heater. As other examples of photothermal treatment upon NIR light, the ondemand dehydration of polyethylene glycol (PEG)-based hydrogels are also provided. All the processes are followed in real time by thermal imaging camera

Safe NIR Light for Fast Polymers Surface Sterilization using Organic Heaters

International audienceSterilization approaches using UV radiation (e.g. 254 nm), dry heat and moist heat have been widely reported in the literature. In the present study, we proposed a most environmentally friendly approach for surface sterilization using safe Near-InfraRed (NIR) light to produce a strong photothermal effect using organic NIR dyes as heaters. Markedly, well selected organic dyes strongly absorbing in the NIR range have been used as stimuli responsive compounds. When excited upon NIR light, these heaters release the light energy to their surrounding environment in the form of heat. In this work, trimethylolpropane triacrylate (TMPTA) based polymers, used as benchmark materials for coatings, could reach high temperatures (> 120°C) in a very short time scale (~30 s). Using heaters containing coatings, sterilization experiments showed very good results with total annihilation of bacteria (Escherichia coli) after only 2 min of NIR irradiation. These results suggest that short irradiation flashes could be enough to sterilize contaminated surfaces. Moreover, some tests have been performed on several NIR heaters in the NIR-II range (1000-1700 nm) for a better in-depth penetration i.e. almost 200°C could be reached by polymers in less than 1 min of NIR irradiation. Therefore, NIR LED irradiation of heater-containing polymers or coatings constitutes here a robust, transportable and safe sterilization method

Concomitant initiation of radical and cationic polymerisations using new copper complexes as photoinitiators: synthesis and characterisation of acrylate/epoxy interpenetrated polymer networks

International audienceTwo new copper complexes were investigated in three-component visible light photoinitiating system for both radical and cationic polymerisation under air. Their reactivity and efficiency have been compared with that of a highly efficient photoredox catalyst G1. The formation of acrylate/epoxy interpenetrated polymer networks were successfully performed through concomitant initiation of radical and cationic polymerisation with low copper complex content upon either LED@405nm or LED@455 nm irradiations. Several characterisations of the acrylate/epoxy IPNs final properties, such as the mechanical properties, adhesion properties, shrinkage and swelling, indicated the possibilities to adapt or tune their properties compared to radical polymerisation of TMPTA

Organic dye‐based photoinitiating systems for visible‐light‐induced photopolymerization

International audienceEven though many organic dyes have been reported as photoinitiators for free radical polymerization in the literature, the design and development of novel photoinitiating systems based on organic dyes and adapted for visible light irradiation e.g. 405 nm LED and sunlight remains still challenging. Recently, major achievements in the development of high-performance photoinitiating systems based on organic dyes as light-harvesting compounds and their uses as photoinitiators for photopolymerization under visible-light irradiation have clearly emerged, giving rise to an abundant literature. In this review, an overview of the recently synthesized chromophores belonging to various families of organic dyes and used as photoinitiators of polymerization during the 2018-2021 period are systematically presented and classified into categories. Recent works have resulted in the development of new chromophores exhibiting remarkable visible light absorption properties and excellent photoinitiation abilities upon irradiation with LEDs and/or sunlight in free radical photopolymerization processes. These developments notably indicate that sunlight has the advantages of being a cheap, unlimited, broad emission spectrum, and energy-saving light source capable to be an efficient substitute to artificial light sources. The newly developed dyebased photoinitiating systems designed to initiate visible light-induced photopolymerization processes is likely to expand the scope of application of photopolymerization in modern sciences and technologies