Effect of thiocarbonylthio compounds on visible-light-mediated 3D printing

Photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization has been successfully employed in three-dimensional (3D) printing to synthesize materials with controlled architecture and diverse functions. However, there is a lack of understanding of the impact of various RAFT agents on the 3D printing process, as only trithiocarbonate RAFT agents were used in the previous systems. In this work, RAFT agents with different activating Z groups and leaving R groups are incorporated in resin formulations and applied to open-air 3D printing systems under mild green light irradiation (λmax = 525 nm, I0 = 0.32 mW/cm2). The Z and R groups of RAFT agents influence the polymerization kinetics and 3D printing process (cure time) and affect the mechanical properties of 3D-printed materials. The impact of the concentration of trithiocarbonates on mechanical properties is also investigated. The 3D-printed materials containing RAFT agents are easily postmodified after printing via one-pot in situ aminolysis and thiol-Michael additions. The RAFT-mediated photoinduced polymerization appears a promising method for producing novel and functional materials.