Conducting Polymers: Polyaniline

Polyaniline is an organic semiconductor. It is prepared by the oxidative chemical or electrochemical oxidations of aniline in acidic aqueous media. The course of the oxidation can be followed by monitoring changes in temperature or pH. Depending on acidity conditions, polyaniline has globular, nanofibrilar, or nanotubular morphology. Polyaniline may also be obtained as thin films, coatings, or as colloidal dispersions. The conducting polyaniline salt convers to nonconducting polyaniline base under alkaline conditions. Its reprotonation by various acids offers a route for preparation of polyanilines with various properties. These processes are reflected in UV–vis, FTIR, and Raman spectra. The mechanism of conduction is based on the presence of delocalized polarons and protons. Polyaniline exhibits both the electronic and ionic conductivity. The stability of polyaniline at elevated temperature and in aggressive media is good. Polyaniline is converted to nitrogen‐containing carbon in inert atmosphere at 600°C. Biological properties and antimicrobial activity of polyaniline are outlined. The applications of polyaniline in batteries, corrosion protection, fuel cells, sensors, and supercapacitors are briefly reviewed.