Reprogrammable 3D-printed liquid crystal elastomers via UV-triggered RAFT interchange.

Reprogrammable liquid crystal elastomers (LCEs) are promising stimuli-responsive materials for soft actuators; however, their integration with digital light processing (DLP) 3D printing is often limited by a lack of dynamic chemistries compatible with radical photopolymerization. Herein, we introduce UV-triggered reversible addition-fragmentation chain-transfer (RAFT) polymerization as a robust solution for spatially selective programming, erasing, and reprogramming of mesogen alignment in printed LCE networks. The resulting networks achieve high-performance actuation (up to 60% strain) and maintain stability over repeated thermal cycles. Beyond actuation, the presence of residual thiocarbonylthio moieties allows for precise surface functionalization after printing. Because RAFT polymerization is inherently versatile, we demonstrate that various macro-RAFT agents can be integrated to tune the material's mechanical properties and actuation characteristics. Ultimately, this RAFT-based platform provides a broadly compatible dynamic platform for reprogrammable LCEs, advancing the manufacturing of multifunctional soft robotic systems.