Abstract: The critical overlap concentration c* of poly (4-vinylpyridine) (P4VP) in a mixed solvent of ethanol and water (V/V=1/1) was determined with viscometry. Afterward, the coordination process and complex structure between P4VP and Cu2+ ions were studied in dilute solution range and semi-dilute solution range with visible spectral method and coordination-conductometric titration method, respectively. The chemical structure of the complex was characterized by FTIR spectra, and the thermal property was measured with differential scanning calorimetry (DSC). The experiment results show that the critical overlap concentration c* for P4VP with Mr=1.06×105 is 15 mmol•L−1. In dilute solution, the intramolecular coordination of the macromolecular chains of P4VP with Cu2+ performs, and a blue soluble complex forms. It was found that the intramolecular complex needed at least nine or ten ligand units per cupric ion owing to the rigidity of polymer chains and the steric hindrance of bulky pyridine rings. Over the critical overlap concentration c*, namely in semi-dilute solution, the intermolecular coordination of the macromolecular chains of P4VP with Cu2+ takes place, an insoluble complex P4VP-Cu(II) forms due to coordination crosslinking, and the coordination number of the complex is three. The glass transition temperature (Tg) of the complex P4VP-Cu(II) is higher than that of P4VP.

Key words: Polymer-metal complex, Complex structure, Poly(4-vinylpyridine), Cu(Ⅱ) ion