title: Stability of polydimethylsiloxane-magnetite nanoparticle dispersions against flocculation: interparticle interactions of polydisperse materials.
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.
authors: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors: O Thompson
authors: OT
authors: Mefford
authors: Michael L
authors: ML
authors: Vadala
authors: Jonathan D
authors: JD
authors: Goff
authors: Matthew R J
authors: MR
authors: Carroll
authors: Raquel
authors: R
authors: Mejia-Ariza
authors: Beth L
authors: BL
authors: Caba
authors: Timothy G St
authors: TG
authors: Pierre
authors: Robert C
authors: RC
authors: Woodward
authors: Richey M
authors: RM
authors: Davis
authors: J S
authors: JS
authors: Riffle
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D005427:Flocculation; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D010316:Particle Size; D012212:Rheology; D012996:Solutions; D013499:Surface Properties
chemical_list: D004129:Dimethylpolysiloxanes; D012996:Solutions; D052203:Ferrosoferric Oxide