Formation Constants of Poly(vinyl alcohol)-Copper(II) Complexes

Abstract

Formation constants for poly(vinyl alcohol)(PVA)-copper(II) complexes were measured by using a modified Bjerrum's method proposed by Gregor and co-workers. The effects of the ratio Teu₂₊/T_HL(the ratio of the total concentration of copper(II) ion to the concentration of the ligand), nature of anion in copper(II) salts and degree of polymerization of PVA on the formation constants were studied in the system of ionic strength 0.1 at 25° C. In all cases, the formation curves of complexes showed that four hydroxy groups combined with one cuprous ion in the pH range above 7.0. The value log b₁, log b₂, log B of PVA-copper(II) complexes increased with increasing Tcu₂₊/T_HL in the range higher than 0.031 (Fig.8), but were unaffected bythe degree of polymerizationof ligand in the range from 400 to 1400. The formation constants increasedin the order of the anion NO₃^-> Cl^-> SO₄^2-, probably because of the complex formed which involved hydrated copper(II) ion(Table 1). The changes of entropy, enthalpyand free energy in the above reaction were determined by the method of Ringbom(Table 2).