A Versatile 3D and 4D Printing System through Photocontrolled RAFT Polymerization.

Reversible addition-fragmentation chain-transfer (RAFT) polymerization is a valuable tool for synthesizing macromolecules with controlled topologies and diverse chemical functionalities. However, the application of RAFT polymerization to additive-manufacturing processes has been prevented due to the slow polymerization rates of typical systems. In this work, we developed and optimized a rapid visible (green) light mediated RAFT polymerization process and applied it to an open-air 3D printing system. The reaction components are non-toxic, metal free and environmentally friendly, which tailors these systems toward biomaterial fabrication. The inclusion of RAFT agent in the photosensitive resin provided control over the mechanical properties of 3D printed materials and allowed these materials to be post-functionalized after 3D printing. Additionally, photoinduced spatiotemporal control of the network structure provided a one-pass approach to 4D printed materials. This RAFT-mediated 3D and 4D printing process should provide access to a range of new functional and stimuli-responsive materials.