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

Abstract

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.

Progress and Perspectives Beyond Traditional RAFT Polymerization

“…In addition to these applications, oxygen tolerance has also significantly simplified the reaction setup for performing surface-initiated polymerizations, [105,106] and for the translation of RAFT into 3D printing. [107,108] Complimenting the observed improvements in interlayer bonding, the application of RAFT holds the promise of finer control over the nano/microstructure of printed materials and the programming of new functions and stimuli-responsivity.…”

3D printing and growth induced bending based on PET-RAFT polymerization

“…Our group has previously worked on RAFT based 3D printing using both iniferter 21 and PET-RAFT 22 processes. Our collaborator the Boyer group have also shown good work with an aqueous based RAFT 3D/4D printing system 15 . The basic recipe for iniferter photo-RAFT 3D printing contains only acrylate monomers to be polymerized and RAFT agent, which is directly activated by the light source.…”

“…However, this forms only half of the solution, with the next choice being which RDRP technique was most appropriate for the task. In recent years Boyer and Xu at UNSW have put significant effort into the development of photo electron/energy transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization, which in simpler terms is a photo-catalyzed mechanism for RAFT polymerization [13][14][15] . Since their initial development in 1998, RAFT processes have shown remarkable versatility as a controlled polymerization technique 16,17 , with notable uses in block copolymerization and self-assembling macromolecules 18,19 .…”

“…25 . This tertiary amine pathway is particularly useful, as it is an oxygen tolerant pathway which is highly desirable and necessary for any 3D printing system 15,22 .…”

Recent advances on push–pull organic dyes as visible light photoinitiators of polymerization

“…If photopolymerization was traditionally devoted to the polymerization of coatings and adhesives due to the wavelength used during the pioneering works in photopolymerization (i.e. UV-light), [2][3][4] the scope of applications has recently been extended to emerging fields such as micro and nanoelectronics, 3D and 4D-printing [5][6][7][8][9][10][11]. Photopolymerization exhibits several appealing features compared to the traditional solution phase polymerization.…”