Cation-Responsive Fluorescence Of Dansyl-Labeled Polyanions Bearing Crown Ether Units

Abstract

Anionic polymers bearing both crown ether units and Dansyl units were prepared by radical terpolymerization of the corresponding monomers, and the effect of cations on the fluorescence properties of the polymers was studied in aqueous media. The fluorescence peaks of the polymers are observed at 500–527 nm. The fluorescence quantum yields (Φ) of the polymers were found to be 6.3 × 10−3−4.0 × 10−1, depending on the polymer structure. On the addition of alkali metal cations, the fluorescence intensity increases in the order LiCl < NaCl < KCl < RbCl < CsCl. The polymer which has almost-equimolar amounts of crown ether groups and–COOH groups shows the highest responsiveness to the cations added. The structure of the anionic moieties in polymers strongly affects the cation-responsive fluorescence. The mechanism for the cation-induced changes in fluorescence is discussed.