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In the realm of polymer-based 3D photo printing, challenges arise from the side effects, notably the persistent presence of photocatalyst residues and metal contamination. These impurities pose significant risks in various applications, including electronics, biological tissues, and medical implants. At the same time, spatial-/time-/light-controlled 3D photo printing has been hindered by low-efficiency polymerization concerning both initiation and monomer conversion. To address these criti-cal issues, a pioneering concept, “degradation-inhibited quench,” is introduced and implemented within photopolymeriza-tion to solve the problems mentioned above. This innovative approach aims to produce pure polymers via higher-efficiency Atom Transfer Radical Polymerization (ATRP) with a unique class of diketopyrrolopyrrole (DPP) derivatives as organo-photocatalysts at an extremely low concentration (as low as 50ppm). Through this approach, pure polymers with ultra-high molecular weight (UHMW) have been successfully synthesized. For instance, poly(methyl methacrylate) (PMMA) achieved a monomer conversion of > 50%, a molecular weight of 2.1 million, and a dispersity of 1.38 after 12 h additional dark reaction. Notably, this novel photopolymerization method demonstrates applicability across a broad spectrum of monomers, with or without solvents, including acrylate, acrylic, styrene, and acrylonitrile. Mechanism insights revealed that the production of UHMW PMMA stemmed from the degradation of intermediate complex DPP•+/Br-, which originated from the photo initiation. This degradation inhibited the oxidative quenching of active propagating chain radicals, thereby significantly extending their lifespan. This groundbreaking concept embraces the potential for further development of highly effective organo-photocatalysts and reactive systems specifically tailored for 3D photopolymerization. Moreover, this novel spatial-/time-/light-controlled polymerization approach does not require any additional purification, offering energy and cost-saving manufacturing technology.
Luo et al. (Fri,) studied this question.