Electrochemically stimulated 2-ethylhexyl phosphate (EHP) release through redox switching of conducting polypyrrole film and polypyrrole/poly (N-methylpyrrole) or self-doped polyaniline bilayers

2-Ethylhexyl phosphate (EHP) released from poly(pyrrole 2-ethylhexyl phosphate) (PP-EHP) was investigated at open circuit and compared with electrochemically stimulated release during potential cycling. It was found that the fast EHP release from the PP-EHP single layer is substantially retarded and that amounts of spontaneously and electrochemically released EHP can be reduced by constructing bilayers, consisting of a PP-EHP inner layer and a poly(N-methylpyrrole)-poly(styrene sulfonate) (PNMP-PSS) or self-doped poly(aniline) sulfonate (SPANI) as the outer films. The presence of outer film over the PP-EHP allowed surface-property modification, as wen as the control of the rate of EHP release, while electrochemically stimulated EHP release from inner films was not substantially hampered by the outer layer. The quantity of the EHP released was investigated using UV-vis spectrophotometery and an electrochemical quartz-crystal microbalance (EQCM) during reduction of PP-EHP from single layer and bilayers through electrochemical stimulation. EHP was reincorporated to the inner film by applying an anodic potential and then the release of EHP was performed again. The results showed that the outer film could act as a barrier to ion-and solvent-transport between the inner film and electrolyte, yielding a more balanced counter-directional movement of anions. (C) 2002 Society of Chemical Industry.