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

Simultaneous initiation of radical and cationic polymerization reactions using the "G1" copper complex as photoredox catalyst: Applications of free radical/cationic hybrid photopolymerization in the composites and

WOS:000469902800007This investigation presents the use of a photoredox catalyst "G1" as a photoinitiating system for free radical/cationic hybrid polymerization under mild irradiation conditions. The G1 system (G1/iodonium salt/N-vinylcarbazole), can simultaneously initiate the free radical and cationic polymerization reactions upon exposure to a visible (405 nm) light from a Light Emitting Diode (LED) source. The multicomponent G1 system is able to simultaneously generate radical and cationic species through a catalytic photoredox process. The curing of thin samples (25 mu m), thick samples (1.4 mm) as well as the manufacture of hybrid system/glass fibers composites ( 2 to 4 mm thickness) was realized and the influence of the ratio of cationic/radical monomer blends on the polymerization kinetics was studied. The use of G1 in visible light photoinitiating system for the access to composites and 3D printing experiments was particularly outlined. G1 was also shown to have low levels of migration from the cured materials. When compared to reference materials ("F1", a similar copper complex and an anthracene derivative, dibutoxy anthracene), G1 showed better polymerization efficiency. The initiation efficiency was investigated through the real-time Fourier transform infrared (RT-FTIR) spectroscopy and optical pyrometry. Dynamical Mechanical Analysis has been used to determine the glass temperature transition of the cured hybrid system as a complementary technique

Photochemistry and Radical Chemistry under Low Intensity Visible Light Sources: Application to Photopolymerization Reactions:

The search for radical initiators able to work under soft conditions is a great challenge, driven by the fact that the use of safe and cheap light sources is very attractive. In the present paper, a review of some recently reported photoinitiating systems for polymerization under soft conditions is provided. Different approaches based on multi-component systems (e.g., photoredox catalysis) or light harvesting photoinitiators are described and discussed. The chemical mechanisms associated with the production of free radicals usable as initiating species or mediators of cations are reported

Monocomponent photoinitiators based on benzophenone-carbazole structure for LED photoinitiating systems and application on 3D printing

In this article, different substituents (benzoyl, acetyl, styryl) are introduced onto the carbazole scaffold to obtain 8 novel carbazole derivatives. Interestingly, a benzoyl substituent, connected to a carbazole group, could form a benzophenone moiety, which composes a monocomponent Type II benzophenone-carbazole photoinitiator (PI). The synergetic effect of the benzophenone moiety and the amine in the carbazole moiety is expected to produce high performance photoinitiating systems (PISs) for the free radical photopolymerization (FRP). For different substituents, clear effects on the light absorption properties are demonstrated using UV-Visible absorption spectroscopy. Benzophenone-carbazole PIs can initiate the FRP of acrylates alone (monocomponent Type II photoinitiator behavior). In addition, fast polymerization rates and high function conversions of acrylate are observed when an amine and/or an iodonium salt are added in systems. Benzophenone-carbazole PIs have good efficiencies in cationic photopolymerization (CP) upon LED @ 365 nm irradiation in the presence of iodonium salt. In contrast, other PIs without synergetic effect demonstrate unsatisfied photopolymerization profiles in the same conditions. The best PIS identified for the free radical photopolymerization were used in three-dimensional (3D) printing. Steady state photolysis and fluorescence quenching experiments were carried out to investigate the reactivity and the photochemistry and photophysical properties of PIs. The free radicals, generated from the studied PISs, are detected by the electron spin resonance - spin trapping technique. The proposed chemical mechanisms are provided and the structure/reactivity/efficiency relationships are also discussed. All the results showed that the benzophenone-carbazole PIs have a good application potential, and this work provides a rational design route for PI molecules. Remarkably, BPC2-BPC4, C6, C8 were never synthetized before; therefore, 5 of the 8 compounds are completely new

Analyse de contours rotationnels de bandes d'absorption vibroniques de cations aromatiques formes par ionisation multiphotonique resonnante: distribution rotationnelle non boltzmanienne

SIGLEINIST T 73601 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Compréhension des mécanismes de photopolymérisation de systèmes sol-gels hybrides (application à la fabrication de microéléments optiques par réticulation spatialement contrôlée)

Les matériaux sol-gels hybrides photopolymérisables (SGH) constituent une solution particulièrement bien adaptée pour le développement de nouveaux dispositifs optiques, leurs propriétés combinant les avantages des polymères et des verres. La synthèse de matériaux SGH est décrite et la caractérisation des réseaux inorganiques (siloxane / titane-oxo) et organiques (polyméthacrylates) les constituant a été réalisée par RMN liquide et solide et FTIR. Les mécanismes de photopolymérisation des formulations SGH ont été étudiés, principalement par FTIR résolue dans le temps. Une avancée significative concerne la mise en évidence du rôle de photoamorceur des alcoxydes de titane. L'utilisation de cette propriété permet d'optimiser la photoréactivité du SGH en contrant l'effet inhibiteur de l'oxygène. Enfin, l'élaboration de micro-éléments optiques adaptés à la connectique optique et leur caractérisation ont été abordées, par utilisation de SGH sensibles dans l'UV et dans le visible.MULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF

Création d'éléments optiques diffractifs par photoréticulation autodéveloppante

A la frontière entre la science des matériaux et l'optique physique, la thèse porte sur la réalisation d'éléments optiques diffractifs dans un système photopolymérisable à base d'acrylates. Sous l'action d'une illumination spatialement contrôlée, la microstructuration du matériau prend place dans le volume, sous forme d'une modulation de densité de matière, donc d'indice de réfraction. Des réseaux holographiques avec des inclinaisons de frange et des fréquences spatiales (de 600 à 4200 mm-1) précisées par les applications sont créés avec succès. Les éléments optiques sont composés d'un ou de plusieurs réseaux superposés dans une me me couche. La duplication dans le matériau photosensible d'hologrammes calculés par ordinateur est aussi considérée. Cette étude conduit à une meilleure connaissance de la réponse du matériau et à des éléments optiques diffractifs ayant des performances encourageantes.Combining material research and optics, the thesis involves an acrylate-based photopolymerizable system which is proposed to create particular diffractive optical elements. Under spatially controlled illumination, the microstructuration takes place in the volume of the material as a modulation of the matter density, corresponding to refractive index variations. Holographic gratings with fringe inclinations and spatial frequencies (from 600 to 4200 mm-1) defined by the expected applications are successfully recorded. The optical elements are formed by one or several gratings created in a unique layer. The duplication of computer-generated-holograms in the photosensitive material is also considered. This study leads to a better understanding of the material response and to diffractive optical elements with encouraging performancesMULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF

Role of Thiol Oxidation by Air in the Mechanism of the Self-Initiated Thermal Thiol-ene Polymerization

International audienceA spontaneous thiol-ene polymerization has been reported in the literature for a broad range of monomers, generally under conditions avoiding solvent, heating and the intentional formation of radicals. In the search for a mechanism accountable to self-initiated thiol-ene polymerization, this study demonstrates the significant role played by thiyl radicals produced by thiol oxidation through dissolved atmospheric oxygen in the thiol-ene mixture. To determine the factors underlying the reactivity, self-initiated polymerization kinetics, thiol solvation and the nature of initiating radicals are studied by means of various techniques including real-time FTIR, 1 H NMR spectroscopy and spin-trapping experiments. Our data support that the driving force for thiol air oxidation is the polarization of the S-H bond. Thiol substituents with electron-withdrawing properties and/or hydrogen-bonded thiol-solvent (or thiol-alkene) complexes favor self-initiation by increasing S-H bond polarization, thereby easing an electron transfer to molecular oxygen

Photogenerating Silver Nanoparticles and Polymer Nanocomposites by Direct Activation in the Near Infrared

This work reports on an improvement of the photochemically assisted synthesis of silver nanoparticles by direct photoreduction of AgNO3 with a laser source emitting in the near infrared range (NIR). For this, polymethine dyes were used as the photoactive agents. Both the effects of central chain structure and activation intensity were investigated. The reduction kinetics was followed up by UV-Vis spectroscopy, and the particles size was evaluated by transmission electron microscopy. The results showed that light intensity affects both the average size and size distribution of Ag nanoparticles generated through this process. The particles can also be generated in situ in a photopolymerizable formulation so that metal/polymer nanocomposites become available through a one-step photoassisted process on the basis of NIR activation. The process described herein is very fast (seconds to a few minutes), and it readily lends itself to automatization for mass production of micro-optical elements implemented directly onto integrated NIR sources

Photopolymerization under various monochromatic UV/visible LEDs and IR lamp: Diamino-anthraquinone derivatives as versatile multicolor photoinitiators

Diamino-anthraquinone derivatives [1,4-bis(isopropylamino)anthraquinone (SB36), 1-amino-4-anilinoanthraquinone (SB68), and 1,4-bis(p-tolylamino)anthraquinone (SG3)] exhibit absorption maxima in red light wavelength range and demonstrate broad ground state light absorption from ultraviolet to infrared light. When combined with coinitiators (e.g. iodonium salt), SB36-based photoinitiating systems exhibit the highest photoinitiation efficiency among all the studied diamino-anthraquinone derivative-based combinations for both cationic and free radical photopolymerization upon exposure to a red LED bulb. And SB36-based systems even demonstrate higher photoinitiating ability for free radical photopolymerization than that of previously studied 1,4-bis(pentylamino)anthraquinone (i.e. oil blue N)-based systems. In contrast, SG3-based photoinitiating systems show the lowest photoinitiation efficiency especially for free radical photopolymerization. Interestingly, the SB36/iodonium salt/N-vinylcarbazole system is a capable multicolor photoinitiating system able to initiate both cationic and free radical photopolymerization under the irradiation of UV to red LED bulbs and IR lamp. The photochemical mechanism associated with the production of cations and radicals from the diamino-anthraquinone derivative-based photoinitiating systems are investigated using steady state photolysis, fluorescence, laser flash photolysis, and electron spin resonance spin-trapping techniques.P. X. acknowledges funding from the Australian Research Council Future Fellowship (FT170100301)