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

Abstract

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. γ-Cyclodextrins (γ-CDs) can selectively recognize the TPE units at the polyurethane chains to afford a PPR. Hydrophilic PEG segments and γ-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 α-amylase are sequentially introduced to cleave the disulfide bonds and cut α-1,4 glycosidic bonds of γ-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.

Multiregulation of Aggregation‐Induced Emission (AIE) via a Competitive Host–Guest Recognition and α‐Amylase Hydrolyzing

“…The host–guest interaction between γ ‐CD and TPE could make the polymer more hydrophilic, dismantles the aggregation, and turn off the fluorescence of the TPE‐PEG in the aqueous medium (Scheme 1B), as demonstrated in our previous study. [ 31 ]…”

“…The host-guest interaction between 𝛾-CD and TPE could make the polymer more hydrophilic, dismantles the aggregation, and turn off the fluorescence of the TPE-PEG in the aqueous medium (Scheme 1B), as demonstrated in our previous study. [31] Upon forming the complexation of TPE-PEG toward 𝛾-CD, the rapid changes of the fluorescence emission from TPE-PEG were studied (Figure 2B). As the curve depicted, when the molar ratio of 𝛾-CD and TPE is 1:1, the intensity of fluorescence rapidly decreases at 455 nm and is suppressed by the host-guest complexation between TPE-PEG and 𝛾-CDs.…”

“…designed a γ‐cyclodextrin ( γ ‐CD)‐TPE host–guest inclusion complex, resulting in the disaggregation of TPE and no fluorescence in water. [ 29,30 ] In our previous study, [ 31 ] the polyrotaxane formed by γ ‐CDs with TPE units could disperse the aggregation state and turn off the fluorescence. The strong fluorescence of an amphiphilic TPE glycyrrhetinate conjugate was suppressed in the presence of γ ‐CDs.…”

Aggregation-induced emission luminogen based self-healing hydrogels fluorescent sensors for α-amylase

“…32 Meanwhile, the host–guest complexation could tune the aggregation of the TPE derivatives, 33 and thus adjust the fluorescence of the AIEgens. 34,35 Hence, it would be desirable to immobilize AIEgens through the host–guest crosslinking of TPE and γ-CD into the hydrogel matrix to achieve self-healing hydrogels, enabling a switchable fluorescence emission. 32,36…”