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

Abstract

ABSTRACT 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.