Conducting polymer photopolymerization mechanism: The role of nitrate ions (NO3−)

This article presents a mechanism that explains the photopolymerization process of the aniline monomer in a medium that contains nitrate ions (NO3−). Polyaniline (PAni) and PAni/Ag0 composite were prepared through the interaction of aniline nitrate, and AgNO3 solution excited by UV light, respectively. In the first case, after UV interaction, the aniline monomer is polymerized while, in the second, PAni/Ag0 composite is obtained. Contrary to what was expected, in the second case, the silver ions Ag+ in the first stage of the process do not seem to be responsible for the polymerization mechanism. Instead, this article shows that the decomposition of NO3− by UV light generates hydroxyl radicals (OH), which are responsible for polymerization of the aniline monomer. In the second stage, the silver ions can be reduced by oligomers produced during the photon polymerization process, which has a low oxidation potential compared to the aniline monomer, to yield the metal particle formation and consequently the metal/polymer composite.