Ethyl(hydroxyethyl)cellulose stabilized polyaniline dispersions and destabilized nanoparticles therefrom

Ethyl(hydroxyethyl)cellulose (EHEC) has been used as a stabilizer for the dispersion polymerization of aniline in water and in aqueous ethanols. An increasingly greater amount of aniline could be used to prepare the dispersion as the ethanol concentration increased in the medium over the range 50-70 vol %. EHEC incorporation in the particles increases and particle size decreases with an increase in the ethanol concentration under otherwise identical experimental conditions. Particles prepared in aqueous ethanols and containing less than ca. 8 wt % EHEC are easily disintegrated to nanoparticles (similar to 20 nm) using ultrasound. These nanoparticles are unstabilized and undergo fractal aggregation even in a medium that contains a substantial amount of EHEC. This fact suggests that in the dispersion polymerization the real stabilizer is not the homopolymer EHEC but could be its graft copolymer. The fractal dimension (D) of the aggregates lies in the range 1.69-1.89. These values agree well with the theoretically determined values of D obtained by computer simulation based on a cluster-cluster aggregation model in three dimensions.