Fluorescence mechanism of poly(2-vinylnaphthalene) driven by local ordering and restricted motion.

The fluorescence mechanism of poly(2-vinylnaphthalene) (P2VN), exhibiting aggregation-induced emission (AIE) characteristics, is systematically investigated through a combination of theoretical calculations and experimental characterizations. Density functional theory (DFT) calculations reveal that, as a π-electron-rich AIE-active polymer, the emission of P2VN originates primarily from the locally ordered stacking of its naphthalene side groups. This ordered arrangement enhances through-space interactions (TSI), which promotes exciton delocalization and significantly increases the fluorescence intensity. Solid-state NMR studies further demonstrate that the restricted molecular motion of naphthalene units is another key factor governing the AIE behavior as it effectively suppresses non-radiative decay and thus improves emission efficiency and intensity. This work elucidates the dual roles of through-space interactions and restricted intramolecular motion in achieving high-efficiency luminescence, providing deeper insights into the AIE mechanism of fluorescent polymers. The findings offer a theoretical foundation for the design of novel luminescent materials beyond traditional conjugated systems.