Polymerization of aniline in the presence of DBSA in an aqueous dispersion

This paper describes a unique process of polymerization in an aqueous medium of an anilinium-dodecyl benzene sulfonic acid (DBSA) complex obtained by reacting aniline with DBSA prior to polymerization, The typical properties of the complex, appearing as fine needles, have been characterized and its polymerization behavior in the presence of DBSA upon addition of ammonium peroxydisulfate in an aqueous medium was investigated by visual color inspection, UV-VIS spectroscopy and pH measurements. The polymerization process was interrupted at different stages and polyaniline (PANI) powders were obtained by precipitation with methanol. The powders morphology was investigated using scanning electron microscopy (SEM) and their electrical conductivity was measured on compression molded strips. UV-VIS and pH measurements show that the average oxidation state of the formed PANI chains vary during polymerization from doped pernigraniline to doped emeraldine and correlate with the dispersion's color. In the beginning of the polymerization course, the SEM studies show agglomerates consisting of spherical PANI particles. As polymerization proceeds, the voids among these particles are filled, forming a smooth surface of the PANI agglomerates, Simultaneously, the conductivity of the PANI powders increases with the polymerization time. (C) 1999 Elsevier Science S.A. All rights reserved.