Orthogonal Photochemistry-Confined Crystallization Enables Mechanically Robust, Printable Shape-Programmable Polymers.

Abstract

Shape-programmable polymers are promising for soft robotics, minimally invasive medicine, and deployable structures. However, integrating high mechanical robustness, versatile shape programmability, and excellent printability into a single material system remains challenging. Here, an orthogonal photochemistry-confined crystallization strategy is developed to fabricate mechanically robust, printable shape-programmable polymers. This approach utilizes a rationally designed photochemical process to trigger radical polymerization and phenol coupling synchronously yet orthogonally, enabling one-step formation of a covalent double-network that efficiently confines polymer crystallization during solvent evaporation. The resulting homogeneous, refined crystalline domains greatly enhance stretchability (1891%) and toughness (41 MJ m^{- 3}) by up to 63- and 103-fold, respectively, compared to counterparts lacking network confinement, while also maintaining fatigue resistance over 1500 stretching cycles. The synergy between confined crystallization and double-network confinement further confers shape reconfiguration and shape‑memory morphing, affording robust shape programmability under thermal stimuli. Moreover, the efficient photo‑mediated gelation, coupled with solvent evaporation, enables rapid and controllable solidification fully compatible with additive manufacturing. Leveraging these capabilities, and as a proof-of-concept, the developed polymers are printed and assembled into bioinspired soft actuators capable of integrated active actuation and precise sensing. This work provides new insight into the photochemical design of high-performance shape-programmable polymers and advanced soft devices.