SURFACE FUNCTIONALIZATION WITH OXOMETALLATES ENTRAPPED IN POLYMERIC MATRICES .3. HOMOGENEOUS VS HETEROGENEOUS-PHASE FORMATION AND EQUILIBRIA OF ISOPOLYTUNGSTATES

The polymerization processes of tungstate anion in acidic aqueous solution are known to be very complex. The main species in these equilibria depend on several factors, including the ratio of protons to tungstate in the solution. Conditions have been selected in which decatungstate should be a major product. However, in homogeneous acidic media, pH 2, irrespective of the anion present (CF3COO-, SO2-4 or C-), it was not possible to observe a clean voltammogram of decatungstate at room temperature. By contrast, it is shown that the influence of poly(4-vinylpiridinium) film (PVP) results in a remarkably stable decatungstate in the polymer matrix, in contact with an acidic aqueous electrolyte at room temperature. This observation attributable mainly to the polymer, and parallels the known stability of decatungstate in non-aqueous solutions. The influence of PVP on the electrochemical behaviour of decatungstate has been studied. © 1990.