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 a lcohol) (PVA) in aqueous solution has been investigated in some detail by using many PVAs ranging in degree of polymerization (DP) from 33 t o 500. The minimum concentration of PVA required to form soluble compl exes has been found to be inversely proportional to its DP, as express ed 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)), res pectively. It has been revealed that iron(III) and copper(II) ions in the complexes exist in the form of metal hydroxide-like clusters compr ising, at most, 120 metal ions per PVA chain. Transmission electron mi crographs for the cast films of an iron(III) complex solution have sho wn the cluster size to be about 30 Angstrom. Poly(vinyl methyl ether), a methyl ether derivative of PVA, was similar to PVA in complex forma tion 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 hydr ophobic interaction.