Introduction From the very beginning of their history, conducting polymers have been considered as infusible and insoluble. It has been an important goal both in basic and in applied research to develop techniques by which these polymers can be processed. Over the last 15 years there has been enormous interest in the preparation of colloidal disper- sions of conducting polymers [1, 2, 3]. Potential applica- tion areas for these colloidal systems include conductive paints, anticorrosion and antistatic coatings, electro- chromatography and immunodiagnostics. There has been extensive work on polypyrrole and polyaniline dispersions prepared chemically in the pres- ence of a surfactant or a polymeric or particulate steric stabilizer [4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. It is interesting to know that the polymeric steric stabilizers employed for the preparation of polypyrrole colloidal dispersions were rather ineffective for the preparation of sterically stabilized polyaniline colloids [14]. Recently, there have been several studies on the use of surfactant-containing media for the electropolymerization of heteroaromatic compounds [15, 16, 17, 18, 19]. The presence of micelles provides an interesting solvent system for the increased solubilization of the heteroaromatics in water. Also, the micellar media affect the electrochemical reactions by irreversible adsorption, leading to a change in the solu- tion–electrode interface properties and producing some template effects at the electrode. Also studies on the synthesis of some substituted polythiophenes and poly- G. Rajasudha D. Rajeswari B. Lavanya R. Saraswathi S. Annapoorni N. C. Mehra Colloidal dispersions of polyindole Received: 6 February 2004 Accepted: 25 June 2004 Published online: 18 August 2004 Ó Springer-Verlag 2004 Abstract Polyindole dispersions consisting of 20–30-nm-sized nano- particles are prepared by chemical oxidation with ferric chloride using sodium dodecyl sulphate, poly(vinyl alcohol) and poly(vinyl acetate) as steric stabilizers. Pure acetonitrile and acetonitrile–water mixtures are used as solvents. The particle size depended on the concentrations of monomer and the steric stabilizer. The dispersions are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform IR spectroscopy, thermal analysis and cyclic voltam- metry techniques. Keywords Conducting polymer Æ Colloidal dispersion Æ Polyindole Æ Polymeric nanoparticles Colloid Polym Sci (2005) 283: 575–582 DOI 10.1007/s00396-004-1189-x ORIGINAL CONTRIBUTION G. Rajasudha Æ D. Rajeswari B. Lavanya Æ R. Saraswathi (&) Department of Materials Science, Madurai Kamaraj University, 625 021 Madurai, Tamil Nadu, India E-mail: saraswathir@yahoo.com Tel.: +91-452-2458247 Fax: +91-452-2459181 S. Annapoorni Department of Physics and Astrophysics, University of Delhi, 110 007 Delhi, India N. C. Mehra USIC, University of Delhi, 110 007 Delhi, India