Water and Secondary Dopants on PAn Crystallinity

Armes and coworkers have investigated the structure of both PAn colloid particles [stabilized with poly(vinyl alcohol)] and electrochemically prepared PAn films. In both cases the fundamental morphology was nanoparticles of up to 20 nm in diameter. Colloid particles were rice grain shaped. Thick films showed submicronsized features that appear to be aggregates of the smaller particles. 

Several other studies have indicated that the PAn film morphology changes during the polymerization process. Abrantes and coworkers,205 for example, used ellip- 

The morphology of in situ deposited PAn s using chemical oxidants is very similar to that of thin electrodeposited films. For thin films (60 nm thick), AFM studies reveal granular features of 50-100 nm in diameter that are densely packed giving smooth films.209 Thicker films are much rougher with granular features up to 200 nm in diameter. 

The growth mechanism of in situ deposited films proposed by Stejskal and coworkers210 has similarities to that described earlier for electrodeposited PAn. It is important to note that the in situ method produces both a surface coating as well as the normal powdery precipitate from the bulk of the solution. It is proposed by 

Stejskal that aniline radical cations adsorb on the substrate surface during an induction period before bulk polymerization is observed. The adsorbed species promote the formation of a dense film initially on the substrate surface. Once this film has formed, further growth occurs on the PAn surface in a manner similar to the growth of localized globules during electropolymerization. The surface roughness of in situ PAn films may be further increased by the incorporation of PAn precipitates from the bulk solution. 

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Influence of Water and "Secondary Dopants" on PAn crystallinity. An increase in crystallinity of PAn emeraldine salt has been reported by the incorporation of secondary plasticizing agents. Pron et al. have shown that... 

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