Photoinitiators of polymerization with reduced environmental impact: Nature as an unlimited and renewable source of dyes

Abstract

The development of new procedures aiming at reducing the environmental impact of polymerization processes is a major societal issue. In this field, light-assisted polymerization and especially visible light photopolymerization can address this issue by enabling in the future, Sun, to be used as the irradiation source. Presently, numerous visible light photoinitiators (xanthene dyes, porphyrins and phthalocyanines) are used in industry but their toxicities constitute a major issue for future uses of polymers. Therefore, photopolymerization is facing a short-term challenge and the development of visible light photoinitiators of polymerization has become a blooming field of research during the last decade. An ever-growing effort is thus done to develop new structures, effort which is also supported by the recent applications of photopolymerization in 3D-printing. Depending on the applications, use of synthetic photoinitiators can constitute a severe limitation for future applications of photopolymers so that the use of natural products has been identified as a promising alternative to address the toxicity or the biocompatibility issues. In this review, an overview of the different visible-light photoinitiators based on natural products is provided.

Recent advances on ferrocene-based photoinitiating systems

“…[8][9] Recently, photopolymerization has known a revival of interest with the development of the 3D/4D printing technologies, and a great deal of efforts has thus been devoted to elaborate dyes strongly absorbing at 405 nm, which is the wavelength currently under use in 3D printers. [10][11][12][13][14][15][16][17][18] With aim at reducing the environmental impact of photopolymerization, greener processes are now widely explored and the use of biosourced photoinitiators and monomers, [19][20][21][22][23][24][25][26][27][28][29] or the use of sunlight as the irradiation source to initiate polymerization processes are now extensively studied. [30][31][32][33][34][35] The progress in these two fields is considerable.…”

“…Figure19. The dual cure process involved during the near-infrared activation of the redox polymerization process.…”

Recent advances on chalcone-based photoinitiators of polymerization

“…[88,163,164] Parallel to this, with regards to the environmental and safety concerns, the development of biosourced and/or bioinspired photoinitiators has become an active research field. [165] Among bioinspired dyes, chalcones have been identified as promising candidates for the design of photoinitiators and these structures are now extensively studied since a couple of years. Chalcones are dyes that can be found in numerous edible plants, vegetables, fruits, spices, and teas.…”

Recent advances on perylene-based photoinitiators of polymerization

“…[26] Considering that the development of visible light photoinitiating systems activable under low light intensity and in the visible range is extremely recent, this research is still in a prospective phase, at the search of innovative structures that could act as visible light photoinitiators of polymerization. In the course of the different investigations, a wide range of structures have been examined and naphthalimides, [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] porphyrins, [42,43] chromones and flavones, [44][45][46][47][48] acridones, [49,50] carbazoles, [51][52][53][54][55][56][57][58] benzophenones, [59][60][61][62][63][64] pyrenes, [65][66][67][68][69][70] diketopyrrolopyrroles, [71]...…”