Fabrication of reversible pH-responsive aggregation-induced emission luminogens assisted by a block copolymer via a dynamic covalent bond

Abstract

Aggregated induced emission (AIE) molecules with stimuli-responsive properties have attracted increasing attention for many applications. Herein, we synthesized a type of block copolymer poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLys) modified with tetraphenylethylene (TPE) via imine bonds (PEG-b-P(Lys-TPE)), which shows reversible pH-responsive AIE characteristics. The presence of pH-sensitive imine bonds enables the reversible detachment of TPE residues from polypeptides with pH variation in the presence of organic solvents, which results in the reversible variation of the fluorescence intensity. We demonstrate that the increase in fluorescence properties is mainly due to the restriction of the intramolecular motion of the TPE moieties during the assembly process of the block copolymer and vice versa, confirming the AIE mechanism. This work offers a convenient and universal strategy to efficiently construct AIEgens with reversible stimuli-responsive properties, which serve as potential candidates for new generations of smart fluorescent nanomaterials.