Abstract:

A well-defined polymer with pendant salicylaldehyde groups(PHVB) was achieved by reversible addition-fragmentation chain transfer(RAFT) polymerization with S-1-dodecyl-S'-(α,α'-dimethyl-α″-acetic acid) trithiocarbonate as the RAFT agent and a salicylaldehyde-functionalized vinyl monomer, 2-hydroxy-5-vinylbenzaldehyde(HVB) in THF at 65 ℃. The resulting well-defined polymer with pendant salicylaldehyde groups can react directly with monoamine-terminated PEG(PEG-NH₂, number-average relative molecular mass 2000 g/mL, 0.5 stoichiometric number of the —CHO group in PolyHVB) to afford an amphiphilic graft copolymer bearing a pendant salicylidene Schiff base PHVB-graft-PEG with 50% grafting density. These new polymers were characterized by GPC and ¹HNMR. Owing to the presence of hydrophilic PEG pendants, PHVB-graft-PEG is capable of self-assembling into nano-sized micelles with salicylidene Schiff base functioned cores, PEG coronas in ethanol. Coordination of the pre-assembled PHVB-graft-PEG micelles with Zn(OAc)₂ will endow the polymeric micelles with fluorescence features, and simultaneously the resulting luminescent micelles may be stabilized by ionic cross-linking in consequence of the complex reaction at the core. Thus, the luminescence properties and form of the obtained micelles were investigated by UV-Vis spectra(UV-Vis), fluorescence spectra(FLL), dynamic light scattering(DLS), transmission electron microscopy(TEM) .After removing ethanol by drying, the resultant Zn²⁺ coordinated particles can be re-dispersed readily in water or common organic solvent to form a micellar solution, which display blue fluorescence with maximum emission peak around 460 nm, indicating the same aggregate size(nearly 100 nm) as before re-dispersion. The obtained luminescent nanoparticles can be used as a highly selective fluorescent probe for Cu²⁺ ion over other metal ions such as Cd^{2 +}, Mg²⁺, Ni²⁺, Pb²⁺, Ca²⁺, Hg²⁺, Al³⁺, Mn²⁺ in aqueous solution, and exhibit a linear range of 0~50 μmol/L and detection limit of 0.05 μmol/L Cu²⁺, respectively.

Key words: reversible addition-fragmentation chain transfer polymerization, aldehyde-amine condensation, salicylaldimine/Zn²⁺ complexes polymers, ionic cross-linking, sensor for Cu²⁺ detection