Influence of chemical polymerization conditions on the properties of polyaniline

The chemical polymerization of aniline in aqueous solutions was studied as a function of a wide variety of synthesis parameters, such as pH, relative concentration of reactants, polymerization temperature and time, etc. The polymer was synthesized using a number of different oxidizing agents and different protonic acids. It was found that the reaction yield was not sensitive to most variables. By contrast, the inherent viscosity of the polymer, measured in solutions in concentrated sulphuric acid, was strongly dependent on the synthesis parameters. Optimum reaction conditions are outlined for the chemical polymerization of aniline, for post-treatment with aqueous HCl solutions, and for compensation of the emeraldine salt into its base form. Under such conditions, high-quality polyaniline base was synthesized with an inherent viscosity (0.1% w/w polymer in sulphuric acid) as high as 2.32 dl g−1.