Orthogonal Reversible Chemistries Affording Multistate Photoswitching in Polymers for Recyclable Intelligent Material Systems

The wide applications of intelligent material systems in robotics, flexible devices, AI-driven techniques, and other high-tech areas call for the development of recyclable intelligent material systems toward a sustainable future. However, intelligent material systems typically comprise multiple components with heterogeneous structures that usually interfere with or cross-contaminate each other during operation or recycling. Here, we design recyclable intelligent material systems based on orthogonal reversible chemistries, specifically photoisomerization of azobenzene and metal-ligand coordination of ruthenium complexes. We create a material, P1-Ru1, by crosslinking an azobenzene-containing polymer with a ruthenium complex. P1-Ru1 switches among multiple states that serve as structural elements, shape-changing modules, adhesives, and other components in intelligent material systems such as soft machines. Crucially, multicomponent, heterogeneous intelligent material systems constructed using different states of P1-Ru1 can be recycled via a one-pot, cross-contamination-free process because all components share the same chemical origin. This work demonstrates that orthogonal reversible chemistries make intelligent responses and recyclability compatible in complex systems. Orthogonal reversible chemistries offer a new strategy for designing recyclable intelligent material systems with multiple components and heterogeneous structures for sustainable high-tech applications.