The oxidation of aniline to produce “polyaniline”: a process yielding many different nanoscale structures

The number of different nano- and micro-scale structures produced from the chemical oxidation of aniline into “polyaniline” is rivaled by few other organic materials. Nanoscale structures such as fibers, tubes, aligned wires, flowers, spheres and hollow spheres, plates, and even those resembling anatomical organs, insects, and sea animals have been observed for the products produced when aniline is oxidized. This feature article examines these different structures and the small and subtle changes in reaction parameters that result in their formation. These changes can often result in drastic differences in the polymer's nanoscale morphology. Because a nanomaterial's properties are highly dependent on the type of morphology produced, understanding polyaniline's propensity for forming these structures is crucial towards tailoring the material for different applications as well as improving its synthetic reproducibility. The different approaches to commonly observed polyaniline nanostructures are presented in this article along with some of the highly debated aspects of these processes. The article ends with our approach towards resolving some of these contentious issues and our perspective on where things are headed in the years to come.