Adsorption of gaseous propylamine on films of polypyrrole in different oxidation states

Quartz crystal microbalance and Kelvin probe were used to investigate the i nteraction between propylamine (PrNH2) vapour and polypyrrole (PPy) films. The films were prepared by oxidative electropolymerization of pyrrole on a platinum electrode in acetonitrile solution. The nature of interaction is s trongly influenced by the oxidation state of the film and co-adsorption of water. On the surface of the oxidized PPy, water adsorbs to form a multilay er. The work function increase of the Pt/PPy electrode exposed to both wate r and PrNH2 vapoures was attributed to the PrNH2 dissolution and dissociati on within the water layer followed by the formatted PrNH3+ cation adsorptio n on the liquid surface with the alkyl group facing the gas phase. On the c ontrary, the water adsorption on the reduced PPy is rather weak and the wor k function decrease observed at the PrNH2 exposure might be connected with the neutral molecules adsorption directly on the polymer surface. The water co-adsorption is documented by a drop in the adsorption of PrNH2 upon lowe ring the water vapour pressure in the gas phase.