Dexter Energy Transfer-Enabled Biobased Oxime Ester-Photosensitizer System for Rapid Visible-Light/Sunlight-Induced Photocuring and 3D Printing

Photopolymerization continues to attract significant interest due to its environmental benefits, precise spatial–temporal control, and energy efficiency. In this study, we report a novel two-component photoinitiating system comprising a synthesized oxime ester derived from biobased carvone and a thioxanthone derivative photosensitizer (isopropylthioxanthone), which effectively addresses the inherent limitations of oxime esters under visible light. Mechanistic investigations, including steady-state photolysis, fluorescence quenching, electron spin resonance spectroscopy, laser flash photolysis, and computational analysis, demonstrate that Dexter triplet–triplet energy transfer is the dominant activation pathway, with a secondary contribution from photoinduced electron transfer. This synergistic mechanism facilitates rapid N–O bond cleavage and decarboxylation, leading to high photopolymerization efficiency under both visible-light and low-intensity solar irradiation. Importantly, the system exhibits excellent storage stability and broad applicability across various 3D printing technologies, including digital light processing, liquid crystal display, and direct laser writing. These findings advance the understanding of visible-light-driven radical generation via dual-energy and electron-transfer mechanisms and provide a promising platform for the development of next-generation photopolymerization-based manufacturing processes.