AIEgen Functionalized Polymer Ring

Intramolecular closure is an effective method to derive polymer rings in which the ends of the parent polymer chains are strongly connected. It is important to develop simple and sensitive methods to discriminate between the intramolecular ring closure and intermolecular cross-linking. Herein, we propose the aggregation-induced emission (AIE) based method to monitor the intramolecular closure of polymer chains. The example polymer of poly(pentafluorophenyl methacrylate)-block-poly(2-(dimethylamino) ethyl methacrylate)-block-poly(pentafluorophenyl methacrylate) (PPFPMA-b-PDMAEMA-b-PPFPMA) is synthesized by RAFT polymerization, and the AIEgens and reactive styryl groups are grafted at the end blocks by reactions with 1-(4-aminophenyl)-1,2,2-triphenylethene and 4-vinylaniline. Along with the electrostatics-mediated intramolecular closure at the dynamic single-chain nanoparticle (SCNP) via ultraviolet (UV)-irradiated radical reaction toward the polymer rings, the AIEgens become highly restricted at the individual cross-linked cluster, giving a rather bright, spectrally narrow emission at 417 nm. In contrast, multiclusters are present at the intermolecularly cross-linked aggregate which are strongly coupled giving an additional red-shifted emission at 480 nm. The resulting AIEgen-functionalized polymer rings therefore combine sharply defined fluorescence signatures with enhanced stability in poor solvents, offering promise as functional optical materials and potential diagnostic probes.