Novel strategy to prepare polyaniline—Modified SiO2/TiO2 composite particles

Abstract

The most commonly used method to deposit polyaniline on TiO2 particles begins with the adsorption of surfactants on TiO2 particles followed by deposition of polyaniline. To avoid the use of surfactants, we propose a novel strategy that employs SiO2 nanoparticles during deposition of polyaniline on TiO2 particles. Thus, polyaniline/SiO2/TiO2 composite particles were successfully prepared during chemical oxidative polymerisation of aniline in a weakly acidic aqueous medium. Polymerisation of aniline in the presence of TiO2 and SiO2 was initiated at pH=3.5 by ammonium peroxydisulphate. Prior to polymerisation, dispersed phases exhibited negative electrophoretic mobility after addition of SiO2 particles into the dispersion of TiO2 particles at pH=3.5. pH measurements conducted during preparation implied that polymerisation was not altered by TiO2 and SiO2 particles. The electrophoretic mobility was modified due to deposition of the polyaniline onto TiO2 and SiO2 particles. The electrophoretic mobility of the composite particles was negative when the amount of TiO2 and SiO2 was high. It gradually turned to positive with increasing proportion of polyaniline to TiO2 and SiO2 in the composite. Particle size measurements and scanning electron microscopy studies showed that agglomeration of the particles occurred during polymerisation. Agglomerate size did not depend on the concentrations of TiO2 and SiO2. Infrared spectroscopy studies indicated that emeraldine salt form of polyaniline was obtained during preparation of the composite particles.