Fully Room-Temperature Reprogrammable, Reprocessable, and Photomobile Soft Actuators from a High-Molecular-Weight Main-Chain Azobenzene Crystalline Poly(ester-amide)

Azobenzene (azo) polymer photoactuators with full room-temperature reprogrammability, reprocessability, and photomobility are highly desirable for large-scale applications, but their development remains a daunting challenge. Herein, a strategy is first presented for fabricating such advanced photoactuators from a high-molecular-weight main-chain azo crystalline poly(ester-amide) (PEA) prepared via Michael addition polymerization. This azo PEA can be readily processed into both physically cross-linked, uniaxially oriented fibers and films with high mechanical robustness and reversible photoinduced bending/unbending at room temperature. Importantly, the presence of both amide unit-induced hydrogen bonding and crystalline domains in such films and fibers endows them with dynamic, yet stable cross-linking points, which enable their easy reprogrammability under strain at room temperature into various three-dimensional (3D) shapes (e.g., film helicoid and spiral ribbon, fiber spring) capable of showing completely different shape-dependent photomobile modes. In particular, these reshaped photoactuators can maintain their accurate 3D shapes and highly reversible photoinduced motions even after being kept at 80 °C for 20 days or at 100 °C for 2 days. They can also be reprocessed and recycled from solution at room temperature. Such a multifunctional main-chain azo crystalline PEA can serve as a versatile platform for fabricating various photoactuators with desired 3D shapes and motion modes under mild ambient conditions.