Photopolymerization processes of thick films and in shadow areas: a review for the access to composites

Garra, Patxi; Dietlin, Céline; Morlet‐Savary, Fabrice; Dumur, Frédéric; Gigmès, Didier; Fouassier, Jean‐Pierre; Lalevée, Jacques

doi:10.1039/c7py01778b

Cited by 154 publications

(158 citation statements)

References 130 publications

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“…[2] Some benefits originate from the fact that NIR light possesses lower scattering coefficients compared to UV light. [3] Furthermore,absorbers applied for physical drying were transferred to the graphics industry for laser drying of printing inks. [4] They also serve as NIR absorbers for laser welding [5] and as sensitizers in the computer to plate (CtP) imaging technology used in modern printing processes.…”

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confidence: 99%

“…Thet emperature increased to 140 8 8C. [17] It was necessary to have an operating matrix that would not evaporate under such conditions.P EGMA additionally provides am atrix similar to that of multifunctional methacrylic monomers.T he use of ah igh-intensity emitting NIR-LED device resulted in the bleaching of both zwitterionic and cationic sensitizers (1)(2)(3)(4)in combination with 5a.F igure 1d epicts the bleaching rates of three sensitizers selected from Table SI3. As expected, the zwitterionic sensitizer 1d1bleached quickly as aresult of PET with 5a.T he cationic sensitizer 1b3 bleaches with less efficiency.T he slowest bleaching rate was observed with Figure 1.…”

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confidence: 99%

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New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

Schmitz¹,

Pang

Gülz³

et al. 2019

Angew Chem Int Ed

165

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Cyanines derived from heptamethines were investigated in combination with iodonium salts as initiators of the radical polymerization of tripropylene glycol diacrylate and epoxides derived from bisphenol‐A‐diglycidylether. A new near‐infrared (NIR) LED prototype emitting at 805 nm with an exposure intensity of 1.2 W cm−2 facilitated initiation of both radical and cationic polymerization using sensitizers derived from cyanines. This new light‐emitting device has brought new insight into the photochemistry of cyanines with the general structure 1 because a combination of photonic and thermal processes strongly influences reaction pathways. In particular, cationic cyanines comprising a cyclopentene moiety and diphenylamino group in the center initiated the cationic polymerization of epoxides. Selective oxidation of this unit explains why specifically these derivatives may function as initiators for cationic polymerization. In contrast, when the diphenylamino group was replaced by a barbital group at the meso‐position cationic polymerization of epoxides was not initiated.

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confidence: 99%

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confidence: 99%

New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

Schmitz¹,

Pang

Gülz³

et al. 2019

Angew Chem Int Ed

165

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“…Well-defined 3D written patterns were obtained with the three-component photoinitiating system Cu-2/(tert-Bu)Ph2I + /NVK (0.2%/5%/1%, w/w/w), notably due to the copolymerization of epoxides and acrylates avoiding the shrinkage effects. However, for numerous industrial applications and especially for the photopolymerization of coatings on complex structures for which the surface cannot be fully exposed to light, the possibility However, for numerous industrial applications and especially for the photopolymerization of coatings on complex structures for which the surface cannot be fully exposed to light, the possibility to initiate a polymerization in shadowed area is actively researched [100]. Concerning this point, a remarkable example was reported with Cu-2 [101].…”

Section: Copper Complexesmentioning

confidence: 99%

Recent Advances on Visible Light Metal-Based Photocatalysts for Polymerization under Low Light Intensity

Dumur

2019

Catalysts

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In recent years, polymerization processes activated by light have attracted a great deal of interest due to the wide range of applications in which this polymerization technique is involved. Parallel to the traditional industrial applications ranging from inks, adhesives, and coatings, the development of high-tech applications such as nanotechnology and 3D-printing have given a revival of interest to this polymerization technique known for decades. To initiate a photochemical polymerization, the key element is the molecule capable to interact with light, i.e., the photoinitiator and more generally the photoinitiating system, as a combination of several components is often required to create the reactive species responsible for the polymerization process. With the aim of reducing the photoinitiator content while optimizing the polymerization yield and/or the polymerization speed, photocatalytic systems have been developed, enabling the photosensitizer to be regenerated during the polymerization process. In this review, an overview of the photocatalytic systems developed for polymerizations carried out under a low light intensity and visible light is provided. Over the years, a wide range of organometallic photocatalysts has been proposed, addressing both the polymerization efficiency and/or the toxicity, as well as environmental issues.

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“…To this end, the development of visible light photoinitiators is also highly researched as the absorption of photoinitiators governs the choice of the irradiation sources and therefore the light penetration [38]. By using long irradiation wavelengths, the polymerization of thick samples and the access to composites is rendered possible, contrarily to the traditional UV photopolymerization for which the polymerization of only thin samples is possible due to a limited light penetration at short wavelength [39]. With regards to these different challenges (light penetration, excited state lifetimes, bleaching properties, molar extinction coefficients), the development of visible light photoinitiators is an active research field imposing new structures to be tested.…”

Section: Introductionmentioning

confidence: 99%

Free Radical Photopolymerization and 3D Printing Using Newly Developed Dyes: Indane-1,3-Dione and 1H-Cyclopentanaphthalene-1,3-Dione Derivatives as Photoinitiators in Three-Component Systems

et al. 2020

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The design of photoinitiating systems with excellent photochemical reactivities at 405nm LED is one of the obstacles to efficiently promote free radical polymerization in mild conditions (e.g., low light intensity, under air). Here, our actual search for new multicomponent photoinitiating systems at 405nm LED prompts us to develop new dyes based on push–pull structures. In the present paper, we chose two series of new dyes which possess indane-1,3-dione and 1H-cyclopenta naphthalene-1,3-dione groups as the electron-withdrawing groups, since they have the great potential to behave as sensitive and remarkable photoinitiators in vat photopolymerization/3D printing. When incorporated with a tertiary amine (ethyl dimethylaminobenzoate EDB, used as electron/hydrogen donor) and an iodonium salt (used as electron acceptor) as the three-component photoinitiating systems (PISs), and among a series of 21 dyes, 10 of them could efficiently promote the free radical photopolymerization of acrylates. Interestingly, steady state photolysis experiments revealed different behaviors of the dyes. Fluorescence experiments and free energy change calculations for redox processes were also carried out to investigate the relevant chemical mechanisms. Additionally, the formation of radicals from the investigated PISs was clearly observed by electron spin resonance (ESR) spin-trapping experiments. Finally, stereoscopic 3D patterns were successfully fabricated by the laser writing technique. In this work, the use of push–pull dyes based on the naphthalene scaffold as photoinitiators of polymerization is reported for the first time in a systematic study aiming at investigating the structure–performance relationship for irradiation carried out at 405 nm. By carefully selecting the electron donors used in the two series of push–pull dyes, novel and high-performance photoinitiating systems operating at 405 nm are thus proposed.

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Photopolymerization processes of thick films and in shadow areas: a review for the access to composites

Abstract: The state of the art for the access to thick samples by photopolymerization processes as well as some perspectives are provided.

Cited by 154 publications

References 130 publications

New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

New High‐Power LEDs Open Photochemistry for Near‐Infrared‐Sensitized Radical and Cationic Photopolymerization

Recent Advances on Visible Light Metal-Based Photocatalysts for Polymerization under Low Light Intensity

Free Radical Photopolymerization and 3D Printing Using Newly Developed Dyes: Indane-1,3-Dione and 1H-Cyclopentanaphthalene-1,3-Dione Derivatives as Photoinitiators in Three-Component Systems

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