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

Abstract

Even though many organic dyes have been reported as photoinitiators/photosensitizers for free radical polymerization in the literature, the design and development of novel photoinitiating systems based on organic dyes adaptable for visible light irradiation, for example, 405 nm LED and sunlight still remains 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 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 presented and classified. 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 dye‐based photoinitiating systems designed to initiate visible‐light‐induced photopolymerization processes are likely to expand the scope of application of photopolymerization in modern sciences and technologies.

New BODIPY Dyes Based on Benzoxazole as Photosensitizers in Radical Polymerization of Acrylate Monomers

“…Upon irradiation with visible light these dyes photosensitize the decomposition of diphenyliodonium salts and active species formation. By using a combination of BODIPY and diphenyliodonium hexafluorophosphate, a nearly complete conversion to the desired polyvinyl polymer was observed after irradiation by a laser at 473 nm for a brief time [19,33]. It was also found that the addition of silanes to the photoinitiating system composed of BODIPY and diphenyliodonium salt increases the efficiency of the photopolymerization.…”

“…It is the chromophore and is often called the photoinitiator (PI) or the photosensitizer (PS). The second one could be an electron donor, an electron acceptor or a hydrogen donor [29][30][31][32][33][34][35].…”

Recent progress in the development of highly active dyeing photoinitiators based on 1,3-bis(p-substituted phenylamino)squaraines for radical polymerization of acrylates

“…98 The basic advantages and disadvantages of squarine-based systems compared with other dyeing photoinitiating systems are summarized in Table 1. 39,86 According to the information in Table 1, both squaraines and other organic dyes can play the role of highly efficient photosensitizers. The photoinitiating ability of dyes depends on their chemical structure.…”

“…98 The basic advantages and disadvantages of squarine-based systems compared with other dyeing photoinitiating systems are summarized in Table 1. 39,86…”

“…37,38 Over the years, the photosensitization abilities of many various organic dyes have been tested. [39][40][41][42] There is much information in the literature on photoinitiating systems containing different types of sensitizers, such as: BODIPY derivatives, [43][44][45][46] camphorquinones, [47][48][49][50] carbazoles, 51-53 coumarins, [54][55][56] cyanines, 40,57 ferrocenes, 58,59 flavones, 60 indoles, 61 squaraines, 40,43,62 thioxanthones [63][64][65][66][67] and many others. 68 The number of compounds that can act as a light absorber is really huge and impressive.…”