Tunable Fluorescence from a Responsive Hyperbranched Polymer with Spatially Arranged Fluorophore Arrays

Abstract

In the present study, a water-soluble hyperbranched polymer platform that contained a Förster resonance energy transfer (FRET) array and exhibited varied fluorescence in response to solvent, light, and CN anion stimuli was constructed. The use of chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization (CuAACP) enabled accurate control of the ratio and distance of three incorporated fluorophores, coumarin (Cou), nitrobenzoxadiazole (NBD), and photoswitchable spiropyran (SP), that could be reversibly transformed into the red-emitting merocyanine (MC) state. Within the FRET system, the energy flow from Cou to MC was significantly enhanced by the introduction of NBD as a central fluorophore relay. Moreover, the energy-transfer efficiency was increased by changing the solvent from tetrahydrofuran to more polar water; this was accompanied by a clear color change and fluorescence behavior. These correlations of polymer composition and solvent polarity to the FRET efficiency were finally applied to the effective detection of CN anion; thus demonstrating a function of this polymer as a CN sensor.

Synthesize Hyperbranched Polymers Carrying Two Reactive Handles via CuAAC Reaction and Thiol–Ene Chemistry

“…One characteristic feature of dendritic polymers is their numerous chain ends largely located at the polymer periphery that have been applied for conjugation with various functional molecules, such as drugs, imaging probes, ligands, and solubilizing groups . Immediately after the CuAACP, the click‐ready azido groups on HBPs were quantitatively reacted with alkyne‐containing guests in situ, where no purification of polymer was required and no additional catalyst was needed . For instance, addition of 1 equiv.…”

“…[48,49] Immediately after the CuAACP, the click-ready azido groups on HBPs were quantitatively reacted with alkyne-containing guests in situ, where no purification of polymer was required and no additional catalyst was needed. [32,50,51] For instance, addition of 1 equiv. of phenylacetylene (to the mole of monomer units) into crude HBP(ene) 300 product completely consumed all azido groups in 6 min and produced HBP(ene) 300 -c-Ph, as evidenced by the disappearance of the azido stretching peak at 2103 cm −1 in Fourier-transform infrared (FTIR) spectroscopy (Figure S3, Supporting Information).…”

Recent advances on synthesis and biomaterials applications of hyperbranched polymers

“…In one such example, light harvesting applications were probed for particles where donor, acceptor and insulator layer thickness could be regulated to achieve highly‐optimized energy transfer for the specific dye molecules used (Shi et al, 2018). Three dyes, coumarin, nitrobenzoxadiazole, and photoswitchable spiropyran, were recently incorporated into a hyperbranched polytriazole in different layers to create a Förster resonance energy transfer array capable of sensing cyanide anions (Cao, Gan, Shi, Xu, & Gao, 2018). Tuning the composition, layer thickness and separation of the fluorophores allowed optimization of the energy transfer and resulted in a polymer with complex stimuli and environmental response behavior.…”

Coordination‐Driven Terpyridine‐Based Twisted Prisms with Tunable Emissions and Hierarchical Self‐Assembly Properties

“…In the past decades, tunable‐fluorescence materials have attracted extensive attention and exhibited a wide range of applications in biological imaging, [ 1 ] environmental sensing, [ 2 ] fluorescent probes, [ 3 ] and other fields, [ 4 ] due to their high sensitivity and stimulus responsiveness. [ 5 ] What is more, tunable‐fluorescence materials, which are affected by external factors, such as temperature, [ 6 ] force, [ 7 ] light, [ 8 ] and solvent, [ 9 ] and internal factors, such as donor–receptor, [ 10 ] π–π interaction, [ 11 ] and host–guest interaction, [ 12 ] play a key role for the development of light‐emitting materials. However, the studies on fluorescent‐tunable materials by hydrophobic interactions are scarce yet.…”

“…Most of the currently reported luminescent SCCs have been constructed using pyridyl‐based ligands with different styles of chromophores. [ 9c,17b,18 ] Among coordination‐driven self‐assembly, 2,2′:6′,2″‐terpyridine (tpy), [ 19 ] which is a donor with a remarkable binding ability to diverse transition‐metal ions with different binding strengths, [ 20 ] has been widely used as a versatile building block to construct various discrete supramolecular architectures, such as 2D metallomacrocycles, [ 21 ] 3D polyhedra, [ 22 ] and prisms. [ 23 ] However, only a few SCCs have been constructed by the combination of terpyridine and fluorescent groups.…”