3D Printing/Vat Photopolymerization of Photopolymers Activated by Novel Organic Dyes as Photoinitiators

Abstract

Even though numerous organic dyes which are used as photoinitiators/photocatalysts during photopolymerization have been systematically investigated and collected in previous reviews, further designs of these chromophores and the developments in high-performance photoinitiating systems have emerged in recent years, which play the crucial role in 3D printing/Vat polymerization. Here, in this mini-review, various families of organic dyes that are used as newly synthesized photoinitiators/photocatalysts which were reported in literature during 2021–2022 are specified by their photoinitiation mechanisms, which dominate their performance during photopolymerization, especially in 3D printing. Markedly, visible light-induced polymerization could be employed in circumstances not only upon the irradiation of artificial light sources, e.g., in LEDs, but also in sunlight irradiation. Furthermore, a short overview of the achievements of newly developed mechanisms, e.g., RAFT, photoinitiator-RAFT, and aqueous RAFT using organic chromophores as light-harvesting compounds to induce photopolymerization upon visible light irradiation are also thoroughly discussed. Finally, the reports on the semiconducting nanomaterials that have been used as photoinitiators/photocatalysts during photopolymerization are also introduced as perspectives that are able to expand the scope of 3D printing and materials science due to their various advantages such as high extinction coefficients, broad absorption spectra, and having multiple molecular binding points.

Recent Advances in Monocomponent Visible Light Photoinitiating Systems Based on Sulfonium Salts

“…Coumarins are biosourced or bioinspired structures [340][341][342] that have been extensively used for the design of photoinitiating systems [343][344][345][346][347][348]. Coumarins, by their absorptions located in the near-UV-visible range, are appropriate photoinitiators for photopolymerization experiments performed at 405 nm, which is the wavelength used in 3D printers [349][350][351][352][353][354]. In 2023, a series of coumarin-substituted sulfonium salts bearing long alkyl chains for solubility was proposed by Liu and coworkers and examined in cationic, free radical and hybrid photopolymerizations (see Figure 38) [355].…”

Recent advances on phenothiazine-based oxime esters as visible light photoinitiators of polymerization

“…A few Type II monocomponent systems have been reported in the literature but examples remain scarce. [42][43][44][45][46] Notably, a series of monocomponent systems based on modified iodonium salts have been proposed by Ortyl and coworkers. [47][48][49][50][51] Another strategy consists in developing Type I photoinitiators i.e.…”

Light‐Mediated Polymerization Catalyzed by Carbon Nanomaterials

“…Light‐mediated polymerization has received increasing interest in polymer synthesis for use in diverse fields [1–19] . Examples include, but not limited to lithography, [4,9,20–22] printing based on 2D, [4,15,23,24] 3D [4,6,8,25–52] or 4D [27–29,53,54] patterning, holographic recording, [16,55,56] fabrication of prosthesis, [57] dental composites, [38,46,58] anti‐counterfeiting materials, [59] inks, [4,60,61] surface modification of solidified coatings [4,13,14,62–68] or adhesives [4,69–72] . Formulating of light‐sensitive compositions based on Chemistry 4.0, which was defined by the VCI in Germany as a combination of artificial intelligence (AI) and central data management, [73] can be seen as an additional challenging aspect [18] .…”