Y. Mori et al., STRUCTURAL INVESTIGATION OF IRON(III) AND COPPER(II) COMPLEXES WITH POLY(VINYL ALCOHOL) BY NMR TECHNIQUES, Polymer Journal, 27(3), 1995, pp. 271-279
Structures of the iron(III) and copper(II) complexes with poly(vinyl a
lcohol) (PVA) have been investigated in full detail by NMR techniques,
especially through analysis of nuclear magnetic relaxation processes
due to paramagnetic metal ions. As a result, it appears well establish
ed that the complexes are of a kind in which iron(III) or copper(II) h
ydroxide-like clusters are included by PVA chains with hydrophobic bac
kbones toward the inside clusters and with hydrophilic OH groups towar
d the outside bulk water, meaning that the interaction between the clu
sters and PVA is of a hydrophobic type. By such an interaction, the co
mplexes have certain definite structures, because there is always a li
near relationship between the H-1 NMR signal intensity of PVA and the
concentration of metal ion in every system of complex formation. In th
e case of the PVA of not less than 250 in the degree of polymerization
, however, there has also appeared another linear relationship with a
more gentle slope over a relatively high concentration range of iron(I
II), suggesting that such PVA molecules can form both complexes contai
ning only one and two or more clusters.