Surface polymerization and precipitation polymerization of aniline in the presence of sodium tungstate

Conducting polyaniline films are spontaneously produced on surfaces immersed in the aqueous reaction mixture used for the oxidation of aniline. When a small amount of sodium tungstate, 0.5-5 mol % relative to aniline, is added into the medium, the induction period of the reaction becomes several times longer and the precipitation polymerization is delayed. The surface polymerization of aniline, which precedes the precipitation mode, then produces thicker polyaniline films. The morphology of the films changes from granular to coral-like at the same time. The conductivity of the polyaniline is moderately reduced as the concentration of tungstate increases.