Polypseudorotaxanes Derived from Tetraphenylethylene: Preparation and Tandem-Activated Aggregation-Induced Emission

Tuning the fluorescence of aggregation-induced emission (AIE)-based materials in a reversible way is essential and a requisite for their applications. The multiple host-guest interactions of polypseudorotaxanes (PPRs) could alter the aggregation state of hydrophobic AIE-based polymeric materials and consequently switch the fluorescence. Herein, tetraphenylethylene (TPE) as a typical AIE molecule has been incorporated into the main chains of the guest polyurethane via a step condensation between poly(ethylene glycol) (PEG)-based dicarbonate and TPE-diamine along with the cleavable disulfide bonds. gamma-Cyclodextrins (gamma-CDs) can selectively recognize the TPE units at the polyurethane chains to afford a PPR Hydrophilic PEG segments and gamma-CD molecules in the PPR could promote the disaggregation of TPE units, suppressing the fluorescence emission of TPE. To restore the aggregated state and fluorescence of TPE units, tris(2-carboxyethyl)phosphine (TCEP) and alpha-amylase are sequentially introduced to deave the disulfide bonds and cut alpha-1,4 glycosidic bonds of gamma-CD, reactivating the AIE behavior of PPR tandemly and accomplishing the reversible cycle of tuning the fluorescence of TPE. The present study provides a tandem way to switch the AIE behavior of polymeric materials reversibly.

Automated summary

This study demonstrates a reversible tuning of fluorescence of aggregation-induced emission (AIE) materials by utilizing multiple host-guest interactions of polypseudorotaxanes (PPRs). The incorporation of tetraphenylethylene (TPE) into polyurethane chains through specific interactions with gamma-cyclodextrins (γ-CDs) allows for efficient switching of TPE fluorescence emission. By introducing tris(2-carboxyethyl)phosphine (TCEP) and alpha-amylase, the reversible cycle of disaggregation and aggregation of TPE units in PPR is achieved.