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The surface polymerization of aniline producing polyaniline nanofilms on surfaces in contact with the reaction mixture has been investigated. The hypothesis that aniline polymerization is heterogeneously catalyzed by the surfaces has been tested. This concept is applicable to planar surfaces and also to surfaces provided by microparticles. The introduction of silica gel, a substrate with a large specific surface area, led to the acceleration of polyaniline formation. The effect of silica gel concentration, particle size, and porosity is discussed, and the courses of polymerization in the presence of porous and compact spheres are compared. It can be concluded that the initiation of aniline polymerization is promoted by adsorption of oligomeric intermediates at the surface. The surface polymerization, giving rise to polyaniline coatings, is thus preferred to precipitation polymerization in the aqueous phase that produces a polyaniline precipitate. The coating of the silica gel surface with polyaniline was not complete, as demonstrated by X-ray photoelectron spectroscopy. The infrared spectrum of the polyaniline coating on silica gel has been compared with that of the PANI film deposited on silicon.

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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.