Polyaniline dispersions 8. The control of particle morphology

Polyaniline dispersions are obtained when aniline is oxidized in an acidic aqueous medium with ammonium peroxodisulfate in the presence of hydroxyprop ylcellulose. The progress of aniline polymerization has been monitored by t he acidity changes and the formation of colloidal particles by dynamic ligh t scattering. Submicrometre spherical polyaniline particles of good uniform ity in size are produced at 0 degrees C, while at 40 degrees C the resultin g objects have coral-like cylindrical morphology. A similar change of parti cle shape has been achieved at 0 degrees C by the acceleration of polyanili ne formation by addition of a mediator, p-phenylenediamine. The concept of the formation of spherical and non-spherical morphologies and the role of t he autoacceleration effect in the dispersion polymerization of aniline are proposed. Polymerization in the frozen reaction mixture at - 25 degrees C y ielded a macroporous composite. (C) 1999 Elsevier Science Ltd. All rights r eserved.