IMMOBILIZATION OF PHOSPHOMOLYBDIC (PM) ACID BY NAFION AND THE ELECTROCHROMISM OF THE RESULTING PM-NAFION FILMS

The electrochromism of phosphomolybdic (PM) acid in solution and immob ilised in Nafion has been investigated. Immobilisation made use of two simple dip-coating techniques which allowed easy modification of the electrochemical activity of the composite films. PM in solution change d from light yellow to blue upon reduction, whereas immobilised PM sho wed a change from pale yellow to light blue under identical conditions . Electrostatic repulsions between PM anions and negatively charged su lfonic groups in Nafion limited the amount of PM that could be molecul arly dispersed in Nafion. This, coupled with the poor conductivity inh erent in the Nafion matrix, resulted in suppressed electrochemical rea ctivities for the composite films. Despite these results, UV-VIS absor ption spectra showed marked differences in light absorption between th e pristine and,coloured forms of immobilised PM, indicative of applica tion potentiality.