Water soluble β-CD-PMAA/PMAm/PHEMA-Coumarin macromolecular fluorescent probes prepared via RAFT method and their sensing ability to Fe3+/Fe2+ and Cu2+ ions

Abstract

Developing water-soluble fluorescent probes has important scientific and practical significance. In this work, coumarin derivatives bearing -OH were obtained through the classical Knoevenagel reaction firstly. Secondly, -CC- on allyl bromide was introduced into coumarin by Williamson ether formation method. Thirdly, hydrazine hydrate was added to the coumarin derivatives, a polymerizable small molecular coumarin fluorophore containing probe was obtained successfully. And, the -COOH on di-thioester underwent an esterification reaction with –OH groups on β-cyclodextrin(β-CD) to prepare oligomer based reversible addition-fragmentation chain transfer(RAFT) reagents. Finally, three copolymer probes β-CD-PMAA-Coumarin, β-CD-PMAm-Coumarin, and β-CD-PHEMA-Coumarin were prepared via RAFT polymerization, in which CC-coumarin was used as the functional monomer and methacrylamide(MAm)/methacrylic acid (MAA)/hydroxyethyl methacrylate (HEMA) as the main monomers. The MALDI-TOF mass tests showed that the macromolecular level probes were successfully prepared. These polymer probes have molecular weights up to 5.4 kDa and have narrow molecular weight distributions (PDI≤1.31). With the assistance of water-soluble long-chained PMAm/PMAA/PHEMA and hydrophilic β-CD, the coumarin containing macromolecular fluorescent probes could be dissolved in water readily. These water soluble polymer fluorescent probes could recognize Fe3+/Fe2+ and Cu2+ ions with high sensitivity. The detection limit of Fe3+ could be as low as 0.34 μM. This study successfully developed a promising technique for producing highly selective, fully water-soluble fluorescent macromolecular probes.