From Preinstalled AIEgens to In Situ-Generated AIE Motifs: Photo-Triggered Dynamic C = S Bond Formation in Polymers for 4D Luminescence Encryption.

Achieving aggregation-induced emission (AIE) in polymers via in situ, real-time generation of chemically explicit emissive motifs, while simultaneously enabling programmable 4D (time-/sequence-dependent) luminescence, remains challenging. Herein, we report a facile platform that converts nonemissive polymer precursors into AIE-active materials through photo-triggered radical reactions that dynamically construct thiocarbonyl (C = S) motifs in polymer backbones. Two kinetically programmable modules are established by molecular design: Switch 1 affords a metastable C = S motif with reversible write-read-erase behavior, and can further evolve into a stabilized thiobenzophenone-like state under prolonged irradiation; Switch 2 yields a more stable C = S motif featuring delayed-write and write-fix characteristics. Spectroscopic evidence supports the radical pathway and reversible/stable C = S formation. By substituent engineering of diphenylmethane-derived cores and sulfur-containing groups, the emission is rationally tuned across the full visible range, supported by quantum-chemical simulations correlating color with frontier-orbital gaps. Leveraging orthogonal control of activation and erasure kinetics via photoinitiators and oxygen-free atmospheres, we demonstrate two modes of 4D fluorescence encryption with time-gated decryption and time-window decoding. This work shifts AIE polymer design from "preinstalled AIEgens" to writable covalent emissive motifs, providing a scalable strategy for smart luminescent coatings and advanced information-security materials.