Preparation of polyaniline by oxidation of aniline using H2O2 in the presence of an iron(II) catalyst

Oxidative polymerization of aniline using the H₂O₂-FeSO₄ system gave polyaniline under mild conditions. The prepared powdery emeraldine base, a form of polyaniline, is blue black and shows high solubility in organic solvents (e.g., ca. 200 mg/mL in N-methylpyrrolidone). The number-average molecular weight (M _n) of the polymer obtained was 1,3–1,7 · 10⁴ (via gel permeation chromatography vs. polystyrene) and M _w/M _n = 1,6–2,2. Poly(2-ethylaniline) and poly-(2-propylaniline) with high molecular weights were also synthesized by this procedure in high yield.