Orthogonal and Multiresponsive Quinolinone Systems for Reversible and Recyclable Polymer Networks.

Achieving precise control over covalent bond formation and cleavage is critical for advancing material recycling and enabling repeated reuse. Here, we introduce quinolinones as versatile, multistimuli-responsive motifs enabling orthogonal and controlled covalent bond manipulation via a reversible [2π + 2π] cycloaddition triggered by light and thermal stimuli. While photochemical bond formation is well-established, thermal reversion of such bonds for material deconstruction remains underexplored. Furthermore, we demonstrate, for the first time, the exceptional ability of quinolinones to undergo symmetrical thermal cleavage, in the solid state with unprecedented efficiency, achieving over 99% monomer recovery at 210 °C within 10 min. This circular process is initially demonstrated at the molecular level, showing an effective cyclability of at least three full bond formation and cleavage cycles with quantitative efficiency. Extending to the macromolecular scale, quinolinones are incorporated into linear polymers to enable phototriggered network formation followed by thermally induced bulk deconstruction. This responsive polymer system highlights remarkable versatility and recyclability. Finally, exploiting their multiresponsivity, quinolinones are applied to advanced coatings with reversible debonding and thermal degradation capabilities. This work establishes quinolinones as a robust platform for stimuli-responsive materials, paving the way for next-generation recyclable systems with enhanced functionalities.