Novel Low‐Cytotoxic and Highly Efficient Type I Photoinitiators for Visible LED‐/Sunlight‐Induced Photopolymerization and High‐Precision 3D Printing

The development of photoinitiators (PIs) combining high initiation ability, low‐toxicity, and availability for high‐precision 3D printing is a key challenge in photopolymerization that has never been reported before. In this study, carbazole chalcone glyoxylate oxime ester derivatives (denoted as Cs, C1‐C5) containing both glyoxylate and oxime ester moieties with good light absorption properties in the visible range have been designed as type I PIs. Subsequent experimental results clearly show that the photoinitiation ability of C5 outperforms that of the benchmark commercial PIs (methyl benzoylformate (MBF) and diphenyl (2,4,6‐trimethylbenzoyl) phosphine oxide (TPO)) under the same conditions. In addition, C5 is successfully applied to 3D printing for the manufacture of large‐scale and high‐resolution object. The photochemical mechanism of C5 is systematically and comprehensively analyzed using a combination of steady state photolysis, decarboxylation reaction, fluorescence experiments, and electron spin resonance‐spin trapping (ESR‐ST) technology. Furthermore, the low‐toxicity of C5 is evidenced by cytotoxicity assays. The comprehensive molecular modeling and experimental approach adopted in this research has led to the development of novel PIs that are highly efficient and low‐toxic, and can be used for high‐precision 3D printing, which offers broad application prospects in the fields of environmental sustainability, visible light curing, and biomedical science.