Recyclable RAFT-3D printing

Recyclable 3D printing systems are urgently needed to address sustainability challenges in polymer manufacturing. Herein, we report a closed-loop 3D printing strategy based on reversible addition-fragmentation chain transfer (RAFT) step-growth polymerization, in which dynamic trithiocarbonate linkages are embedded into the polymer network. The resulting network is recyclable <i>via</i> RAFT interchange under 405 nm irradiation in the presence of excess RAFT agents, regenerating oligomers bearing reactive chain-end groups. These intermediates can be directly re-crosslinked by adding stoichiometric vinyl monomers, thereby reconstructing the original polymer structure. Moreover, upcycled materials can be easily obtained by varying the vinyl monomer concentration. Digital light processing (DLP)-based 3D printing of these resins yields robust objects with tunable mechanical properties (Young's modulus from 0.78 to 835 MPa). Post-printing functionalization and erasure <i>via</i> RAFT interchange further demonstrate the dynamic and "living" features of this system. This catalyst-free, modular approach eliminates the need for specialized dynamic covalent monomers, offering a practical and sustainable platform for recyclable RAFT-based 3D printing.