Bridging the gap between performance and biocompatibility: non-toxic, multifunctional aliphatic photoinitiators based on α-ketoesters for lithography-based manufacturing applications

Abstract

Photoinitiators (PIs) represent the key molecules within a photopolymerizable resin, due to their ability to generate the initiating species. However, the majority of state-of-the-art PIs comprise aromatic chromophores, known to produce cytotoxic photoproducts, whose migration out of the cured resin poses both environmental and human health threats. Herein, we present a set of multifunctional, aliphatic free radical photoinitiators based on the α-ketoester moiety, which exhibit low cytotoxicity even after irradiation. By systematically increasing the number of PI moieties, purely aliphatic molecules comprised of up to four radical-generating units have been synthesized. High miscibility in both organic and water-based formulations, combined with excellent photoreactivity and no discoloration upon irradiation with broadband (320–500 nm) and LED (385 nm) light sources, are demonstrated. The developed α-ketoester derivatives outperform the benchmark Norrish type II benzophenone/amine system and can be used for advanced applications, including UV-nanoimprint lithography as well as additive manufacturing technologies (DLP 3D printing).