Quasi-elastic light scattering study of the synthesis of tailor-made suspensions of uniform polyaniline-based nanoparticles

The understanding of the mechanism of aniline oxidative polymerization allows one to regulate the synthesis of the colloidal particle suspensions in such a way that a product of controlled average particle size and particle size distribution is obtained. Quasi-elastic light scattering was used to determine these parameters for the particles taken from a reaction mixture at various stages of the polymerization. It has been found that the particle size and the particle size distribution of the product depend on the reactiveness of the monomer (m-, o-toluidine, or aniline),on the concentrations of the monomer, oxidant and stabilizer-poly(vinyl alcohol-co-acetate), and on the temperature. The particles of uniform size are formed within a limited period of rime during the polymerization; in some cases until termination. Their sizes lie within the range of 200-600 nm for the polyaniline and within 400-3000 nm for poly(m-toluidine). Comparison of the prepared samples with commercially available uniform poly styrene latex standards shows that the polyaniline- and poly(toluidine)-based particle suspensions exhibit at least the same but in most cases narrower particle size distributions.. The obtained color particles can be used in many practical applications, for example, as markers for studies of the transport phenomena in colloidal suspensions.