Synthesis and characterization of carboxylic acid functionalized polypyrrole silica microparticles using a 3-substituted pyrrole comonomer

A series of carboxylated polypyrrole-silica microparticles were synthesized by copolymerizing pyrrole-3-acetic acid with pyrrole using a hydrogen peroxide-based oxidant in the presence of an ultrafine silica sol. The effect of varying the proportion of pyrrole-3-acetic acid in the comonomer feed on the physicochemical properties of the resulting carboxylated microparticles has been examined. The particle size distributions and morphologies of the microparticles were assessed using disk centrifuge photosedimentometry and transmission electron microscopy. The compositions of the microparticles were determined using thermogravimetry (silica content) and microanalyses (conducting polymer content), respectively. The surface compositions of the microparticles were examined using X-ray photoelectron spectroscopy and zeta-potential measurements. Increasing the proportion of the pyrrole-3-acetic acid in the comonomer feed led to higher degrees of surface carboxylation, as expected. The reproducibility of these microparticle syntheses was significantly improved compared to that of similar dispersions synthesized using an N-substituted pyrrolic comonomer in an earlier study. Finally, these new microparticles exhibited improved colloid stability after long-term storage under ambient conditions.