Dual responsive spiropyran-ended poly(N-vinyl caprolactam) for reversible complexation with metal ions

With the spiropyran-containing compound as the initiator, dual responsive spiropyran-ended poly(N-vinyl caprolactam) (SP-PNVCL) was synthesized by atom transfer radical polymerization. The structure of the resulting polymer was characterized by 1 H NMR and gel permeation chromatography, and the polymer had both reversible light-responsive and thermo-sensitive behaviors. Metal ions could be bound between merocyanine formed by photoisomerization of spiropyran and the amino group of N-vinyl caprolactam unit through synergetic coordination. The complexation of SP-PNVCL with several metal ions was investigated by UV-Vis absorption spectroscopy, and it was found that SP-PNVCL might be used as a potential recognition probe for Fe 2+ , accompanied by obvious color change from colorless to brown by naked eye. The detection limit and photo-reversible recyclable behaviors of SP-PNVCL for Fe 2+ were also investigated in details. The kind of spiropyran-ended poly(N-vinyl caprolactam) had great application potential in environment protection and biological area.