Tunable and wavelength-gated reversible photopolymerization of quinolinone-based telechelic oligomers via [2π + 2π] cycloaddition

Abstract

Gated photochemistry provides a powerful strategy for modulating polymer architecture under mild conditions through light-controlled reversible bond formation. Quinolinone-based photoactive units are introduced as a robust and tunable motif for reversible [2π + 2π] photocycloaddition, enabling wavelength-gated photopolymerization and depolymerization. Telechelic macromonomers bearing quinolinone end groups undergo efficient light-triggered polymerization to yield high-molecular-weight polymers (M_p ≈ 60 000 Da), followed by nearly complete depolymerization back to the original macromonomers under distinct irradiation wavelengths—without catalysts or additives. Systematic investigation of oxygen concentration, irradiation wavelength, and monomer concentration revealed a complex interplay governing reaction efficiency and reversibility. Oxygen enables red-shifted operation (up to 45 nm) and modulates the photostationary equilibrium, while concentration determines the balance between intermolecular chain extension and intramolecular cyclization. This wavelength- and environment-tunable photochemical response achieves reversible polymer formation, including under ambient conditions. The demonstrated tunability and reversible behavior establish quinolinone-based photoswitches as a versatile platform for recyclable and reprocessable light-responsive polymer systems.