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.