Siloxane‐Activated Through‐Space Conjugation in Conventional Chromophores for Dual‐State Emission

ABSTRACT While through‐space conjugation (TSC) offers a powerful paradigm for constructing luminescent materials beyond planar π‐systems, its deliberate integration and activation within conventional chromophoric frameworks to enhance emission remains a fundamental challenge. We address this by designing siloxane‐linked fluorescent polymers (SFPs), synthesized via straightforward Heck reactions using 1,3‐divinyl‐1,1,3,3‐tetramethyldisiloxane and bi‐, tri‐, or tetra‐brominated aromatic monomers. The siloxane linkage is not merely a passive spacer but actively mediates efficient TSC, endowing the polymers with remarkable dual‐state emission. Notably, spirobifluorene‐based polymer SFP‐2 achieves photoluminescence quantum yields of up to 92.7% in solution and 23.4% in the solid state. Theoretical and spectroscopic analyses elucidate a “dynamic encapsulation” mechanism, wherein the flexible siloxane chain wraps two chromophores into a spatially proximate, non‐covalently coupled assembly. This configuration suppresses intramolecular vibrational relaxation in solution, while chain entanglement in the solid state creates isolated microenvironments that inhibit aggregation‐caused quenching. Leveraging this unique photophysics, the materials function as selective “turn‐off” fluorescence probes for trifluralin detection under daylight and UV light, and as effective components in UV‐shielding films. This work establishes a general “siloxane‐activated TSC” design strategy, fundamentally underscores the active role of siloxanes in modulating optoelectronic properties, and highlights their potential in flexible electronics and sensing technologies.