Rapid high-resolution 3D printing and surface functionalization via type I photoinitiated RAFT polymerization

RAFT facilitated digital light projection 3D printing of polymeric materials provides a convenient and facile route for inducing post-fabrication transformations via reactivation of dormant chain transfer agents. In this work, we report the use of a Norrish type I photoinitiator in conjunction with a RAFT agent to produce a variety of open-air 3D printable resins that rapidly cure under visible light irradiation. The photoinitiator-RAFT system polymerizes extremely quickly and provides high 3D printing build rates of up to 9.1 cm h⁻¹, representing a 7-fold increase compared to previous RAFT mediated 3D printing systems. 3D printed materials containing thiocarbonylthio groups can be also produced using low concentrations of divinyl comonomers in the initial resins, which has not been successfully achieved using other photocontrolled RAFT polymerization techniques. Interestingly, the inclusion of RAFT agents significantly improves 3D printing resolution compared to formulations without RAFT agent, allowing the fabrication of intricate and complex objects. Spatiotemporally controlled surface modifications of the 3D printed objects from the dormant RAFT agent groups on the material surfaces were also performed under one and two-pass configurations, inducing multiple successive post-printing transformations on the same object.