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.