A method for preparation of organo-soluble polyaniline (PANI) is described. Oxidative coupling polymerization of anilium chloride with ammonium persulfate in anew ionic liquid, 2-hydroxyethyl ammonium formate (HAF), gives organo-soluble polyaniline with appreciable molecular weights (M-w = 86,400). Interestingly polyaniline (PANT) prepared by this method is highly soluble in many organic solvents such as acetone, tetrahydrofurane, dioxane, dimethyformamide and N-methyl, 2-pyrrolidinone. Thin films of PANI prepared at 0 degrees C (by solvent casting) show reasonable conductivities (up to 37.0 S cm(-1)) when doped with p-toluene sulfonic acid. (C) 2005 Elsevier B.V. All rights reserved.