Effect of Various Parameters on the Stability of Silica Dispersions Qaisar Abbas Bhatti • Musa Kaleem Baloch • Simona Schwarz • Gudrun Petzold Received: 10 March 2013 / Accepted: 19 June 2014 / Published online: 12 November 2014 Ó Springer Science+Business Media New York 2014 Abstract For different practical applications, it is cardinal to maintain the stability of nanoparticles in aqueous suspension. The theoretical impact of pH and ultrasonication time on surface charge, particle size distribution and the dispersion stability of AEROSIL Ò OX 50 in water were evaluated, and a practical (centrifugal sedimentation analysis) test was used to determine the effects of concentration and molar mass of the polymer polyvinyl- pyrrolidone (PVP) at different pHs. It was observed that the size distribution of silica remains almost unaffected, but the surface charge increased with ultrasonication time up to 20 min and then leveled off. This increase in surface charge was proportional to the molar mass of the added polymer. The zeta potential increased with the increasing concentration of PVP in the silica suspension. This behavior is attributed to the adsorption of polymer over the surface of the particles. The suspensions were found to be the most stable, up to 36 %, at concentration (1 %) of PVP having higher molar masses. Furthermore, the addition of polymer strengthened the available agglomerates in the dispersion which resulted in the widening of the particles’ size distribution. Keywords Particle size distribution  Ultrasonication  pH  Zeta potential  Surface charge  Molar mass of poly(vinylpyrrolidone)  Stability of silica dispersion 1 Introduction The stability of colloidal suspensions in the presence of macromolecules is thought to be the result of polymer adsorption on the particle’s surface, which imparts steric or Q. A. Bhatti (&)  M. K. Baloch Department of Chemistry, Gomal University, Dera Ismail Khan, Pakistan e-mail: kais_chem@yahoo.com S. Schwarz  G. Petzold Leibniz-Institut fu ¨r Polymerforschung, Dresden e.V., Dresden, Germany 123 J Solution Chem (2014) 43:1916–1928 DOI 10.1007/s10953-014-0260-6