Mechanical Stretch α-Cyclodextrin Pseudopolyrotaxane Elastomer with Reversible Phosphorescence Behavior.

Polyethylene glycol chains in two terminals of the naphthalene functional group are threaded into α-cyclodextrin cavities to form the pseudopolyrotaxane (NPR), which not only effectively induces the phosphorescence of the naphthalene functional group by the cyclodextrin macrocycle confinement, but also provides interfacial hydrogen bonding assembly function between polyhydroxy groups of cyclodextrin and waterborne polyurethane (WPU) chains to construct elastomers. The introduction of NPR endows the elastomer with enhanced mechanical properties and excellent room temperature phosphorescent (RTP) emission (phosphorescence remains in water, acid, alkali, and organic solvents, even at 160 °C high temperatures). Especially, the reversible mechanically responsive room temperature phosphorescence behavior (phosphorescence intensity increased three times under 200% strain) can be observed in the mechanical stretch and recover process, owing to strain-induced microstructural changes further inhibiting the non-radiative transition and the vibration of NPR. Therefore, changing the phosphorescence behavior of supramolecular elastomers through mechanical stretching provides a new approach for supramolecular luminescent materials.

Water/Light Multiregulated Supramolecular Polypseudorotaxane Gel with Switchable Room-Temperature Phosphorescence.

Water/light regulated room-temperature phosphorescence (RTP) of polypseudorotaxane supramolecular gel is constructed by threading the poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) chain with the bromoaromatic aldehyde into mono-(6-ethylenediamine-6-deoxygenated)-ß-cyclodextrin (ECD) cavities and further assembling with negatively charged Laponite XLG (CNS) and diarylethene derivative (DAE) through electrostatic interaction. This hydrogel exhibits significant blue fluorescence emission; instead, after lyophilization to xerogel, the system exhibits both blue fluorescence and yellow RTP based on the rigid network structure of the xerogel, which restricts the vibration of the phosphor and suppresses the nonradiative relaxation process. Interestingly, the addition of excess ECDs to the gel system can enhance the RTP emission. Furthermore, the reversible luminescence behavior can be adjusted by the photoresponsive isomerism of DAE and humidity. This polypseudorotaxane supramolecular gel system provides a novel strategy for constructing tunable RTP materials.