Stability of polydimethylsiloxane-magnetite nanoparticle dispersions against flocculation: Interparticle interactions of polydisperse materials

O.T. Mefford, M.L. Vadala, J.D. Goff, Matt Carroll, R. Mejia-Ariza, B.L. Caba, Tim St Pierre, Rob Woodward, R.M. Davis, J.S. Riffle

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

The colloidal stability of dispersions comprised of magnetite nanoparticles coated with polydimethylsiloxane (PDMS) oligomers was investigated theoretically and experimentally. Particle-particle interaction potentials in a theta solvent and in a good solvent for the PDMS were predicted by calculating van der Waals, electrostatic, steric, and magnetic forces as functions of interparticle separation distances. A variety of nanoparticle sizes and size distributions were considered. Calculations of the interparticle potential in dilute suspensions indicated that flocculation was likely for the largest 1% of the population of particles. Finally, the rheology of these complexes over time in the absence of a solvent was measured to probe their stabilities against flocculation as neat fluids. An increase in viscosity was observed upon aging, suggesting that some agglomeration occurs with time. However, the effects of aging could be removed by exposing the sample to high shear, indicating that the magnetic fluids were not irreversibly flocculated.
Original languageEnglish
Pages (from-to)5060-5069
JournalLangmuir
Volume24
Issue number9
DOIs
Publication statusPublished - 2008

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