STUDIES ON THE COMPLEX-FORMATION BETWEEN IRON(III) OR COPPER(II) AND POLY(VINYL ALCOHOL) IN TERMS OF INCLUSION OF THE METAL HYDROXIDE-LIKE CLUSTERS BY THE POLYMER

The complex formation between iron(III) or copper(II) and poly(vinyl alcohol) (PVA) in aqueous solution has been investigated in some detail by using many PVAs ranging in degree of polymerization (DP) from 33 to 500. The minimum concentration of PVA required to form soluble complexes has been found to be inversely proportional to its DP, as expressed by the constancy of (DP of PVA)x[PVA]; the constants were 13 and 15 M in 10 mM iron(III) and copper(II) solutions (1 M=1 mol dm(-3)), respectively. It has been revealed that iron(III) and copper(II) ions in the complexes exist in the form of metal hydroxide-like clusters comprising, at most, 120 metal ions per PVA chain. Transmission electron micrographs for the cast films of an iron(III) complex solution have shown the cluster size to be about 30 Angstrom. Poly(vinyl methyl ether), a methyl ether derivative of PVA, was similar to PVA in complex formation with iron(III) up to pH 5. This fact also supports the conclusion that the present PVA complexes are of an inclusion type due to a hydrophobic interaction.