Hybrid materials Polypyrrole/PW12O403-. 2. Physical, spectroscopic and electrochemical characterization

Physical, spectroscopic and electrochemical information on the potentiostat ically synthesized hybrid material polypyrrole/PW12O403- was obtained by me ans of electron microscopy, W-vis spectroscopy, in situ UV-vis absorption - reflection spectroelectrochemistry, FTIR spectroscopy, EDX and cyclic volta mmetry. The hybrid shows a very flat morphology and a two-layer structure a fter its generation. By reduction, the external layer, 76% weight of the ma terial, is electrodissolved. This fraction contains PW12O403- anions and py rrole oligomers. Continuous potential cycling of the insoluble hybrid adher ed to the electrode gives rise to an increasing concentration of polyoxomet alate in the background solution, thus proving that phosphotungstate anions were gradually rejected from the film. Films before and after electrodisso lution of the soluble fraction show similar flat morphology. The insoluble fraction undergoes a strong morphological change during potential cycling, keeping almost constant both weight and stored charge. The oxidized state o f the electrosoluble layer is partially soluble in DMSO and in mixtures of PC and EC, thus opening new ways for processing those materials. The two-la yer structure of polypyrrole-based hybrid materials was also observed for o ther polyoxometalates, synthesized in different electrolytic media.