Radical Synergy Between Initiating and Inhibitor Species Enables Kinetically Controlled Holographic Polymerization

Achieving precise kinetic control over photopolymerization remains a central challenge for fabricating high-performance holographic polymer-liquid crystal composites (HPDLCs). Herein, we report a dual-radical system that leverages the synergy between an initiating thiyl radical and an inhibitor-type ketyl radical, both generated in situ from a photoactive chromophore pair, 2,5-bis[4-(diethylamino)benzylidene]cyclopentanone (BDEA) and 2-mercaptobenzoxazole (MBO). In this system, the ketyl radical acts as a chain-terminating species that quenches undesired chain propagation in destructive interference regions, thereby amplifying the gelation time disparity between bright and dark zones and facilitating phase separation. Strikingly, the addition of biimidazole (HABI) converts the ketyl radical into a new initiating species, which diminishes the gelation-time disparity and suppresses phase separation. External inhibitors such as xanthone (XAN) fail to replicate this modulatory function, underscoring the indispensable role of internally coordinated radical interactions. This cooperative radical mechanism not only enables high-fidelity, full-color holographic patterning, but also establishes a conceptual framework for kinetic modulation through internal radical interplay.