Photoinduced Free Radical Promoted Cationic RAFT Polymerization toward "Living" 3D Printing

Three-dimensional (3D) printing utilizing controlled polymerization systems is emerging as a powerful approach to fabricate "living" objects, which can be further modified with various functionalities. Here, we report photoinduced free radical-promoted cationic reversible addition-fragmentation chain transfer (RAFT) polymerization under broad wavelengths from ultraviolet (UV) to near-infrared (NIR) light. A commercially available iron catalyst, cyclopentadienyl iron dicarbonyl dimer (Fe₂(Cp)₂(CO)₄), was used as the photocatalyst, and several diphenyliodonium salts were examined as oxidants. Various poly(vinyl ether)s with controlled molecular weights and a narrow dispersity (1.06-1.32) were prepared through this method. Relatively high chain-end fidelity can be observed and has been demonstrated by successful chain-extension experiments. In addition, benefiting from the penetrating ability of NIR light, 3D objects with different thicknesses were achieved by employing stereolithography-based 3D printing techniques. Furthermore, the postfunctionalization of these 3D printed objects with fluorescent monomers provides a facile method to build 3D objects with complex functionality and potential applications in anticounterfeiting materials.