Hierarchical Coordination Polymer-Polymer Composites for Robust, Programmable Photomechanical Actuation.

Abstract

Photoresponsive coordination polymers offer precise molecular-to-macroscopic control of mechanical motion, yet their brittleness and limited processability constrain practical implementation. Here we report a hierarchical composite strategy that embeds a one-dimensional Zn(II) coordination polymer capable of topochemical [2+2] cycloaddition within a poly(vinyl alcohol) matrix and coats it with poly(ε-caprolactone), yielding mechanically robust, scalable, and water-stable photomechanical films. The composites exhibit wavelength-selective activation and expansion-programmable deformation, enabling dual-stage bending and radial expansion with actuation fidelity exceeding 98% over extended storage and radial strengths approaching those of load-bearing polymeric systems. Comparative analysis across representative photoactuating materials identifies a distinct regime combining crystalline photochemical precision with macroscopic mechanical resilience. These results establish general design principles-topochemical preorganization, hierarchical stress transfer, and protective coating-for translating lattice-confined photochemistry into durable, expansion-programmable mechanical actuation, providing a foundation for next-generation adaptive and deployable material systems.