3D printing polymerizable eutectics via RAFT polymerization†

Over the past five years, there has been a notable increase in the application of three-dimensional (3D) printing techniques mediated by reversible addition–fragmentation chain-transfer (RAFT) polymerization. This increasing interest is due in part to the associated benefits that RAFT 3D printing systems provide, including tighter control over macromolecular network structures and the ability to easily prepare multifunctional materials. In parallel, deep eutectic solvents that feature polymerizable components, called polymerizable eutectics, have also been gaining attention for their outstanding properties and ease of manufacture of functional polymer materials. In this work, we develop polymerizable eutectic resins that contain RAFT agents and are suitable for application to visible-light induced vat 3D printing. The combination of the polymerizable eutectic components and a Z-connected bis-RAFT agent in the resin provides the resulting materials with excellent properties derived from both the eutectic components and the degenerative chain transfer mechanism of RAFT polymerization. While the base (non-RAFT) polymerizable eutectic materials display high modulus and adhesive strength on their own, the inclusion of RAFT agents provides materials with higher adhesive strength while retaining their high strength to higher temperatures. Moreover, the selection of N-isopropylacrylamide as one of the eutectic components provides these materials with reversible thermoresponsive behavior in water. The high shape fidelity and ease of preparation of these materials could be of potential use in the design of 3D printable biomaterials and actuators.