Photothermal solid-to-liquid transition in a coordination polymer: strength enhanced by coordination bond-induced nanoconfinement

Polymers exhibiting photoinduced solid-to-liquid phase transitions have garnered significant attention due to their potential applications in smart materials. However, the simultaneous achievement of high strength and extensibility remains a significant challenge. In this work, we present an innovative approach to overcome this limitation by incorporating coordination bonds into the polymer backbone. Specifically, we have developed a photothermal solid-to-liquid transition polymer (PSLTP) based on PTMG oligomers end-capped with ligand motifs that coordinate with lanthanide (La3+) ions. Upon exposure to 365 nm light, the polymer efficiently absorbs photons and converts them into thermal energy, inducing the dissociation of coordination bonds and triggering a reversible solid-to-liquid phase transition. The resulting nanoconfinement phases, due to coordination bond-induced structures, significantly enhance the polymer's mechanical properties, including a tensile strength of 22 MPa and a break elongation of 1240%. These unique properties render the polymer particularly promising for applications requiring reversible bonding and self-healing capabilities for large-scale damages. This study underscores the potential of coordination bond-based systems in the design of photothermal polymers, offering insights into their underlying mechanisms and practical applications in responsive materials.