Phase transfer of agglomerated nanoparticles: deagglomeration by adsorbing grafted molecules and colloidal stability in polymer solutions

  • Martin Rudolph
  • Urs Alexander Peuker
Research Paper


A study is presented, where agglomerated magnetite nanoparticles with a crystallite size of 15 nm are transferred from water to an immiscible organic phase and tend to deagglomerate under certain conditions using different types of chemically adsorbing fatty acid. It is shown that the longer fatty acids lead to more stable dispersions and for the longest fatty acids, the functionality of the molecules defines stability with best results for ricinoleic acid. The disjoining force as a function of the brush layer thickness and adsorption density is calculated with a physical model applying the well-established Alexander de Gennes theory. We further investigate the colloidal stability of the transferred and stabilized magnetite nanocrystals in polymer solutions of destabilizing PMMA and stabilizing PVB. A DLVO-like theory presents the governing attractive and repulsive interactions for the case of destabilizing non-adsorbing polymers. The theory can be used to explain the influencing parameters in a mixture of sterically stabilized nanoparticles in an organic solvent based solution of polymer coils. Finally, by spray drying, we produce polymer–nanoparticle composite microparticles. Based on BET, laser diffraction and backscatter electron SEM measurements, we draw conclusions on the nanoparticle distribution within the composite in correlation with the stability investigations.


Disjoining force Peptization Resuspension Depletion Fatty acids Polymer Solvents Magnetite Steric interactions Solubility distance DLVO Non-DLVO Nanocomposites 



Alexander de Gennes theory


Caprylic acid




Dynamic light scattering


Linoleic acid


Myristic acid


Oleic acid


Poly(methyl methacrylate)


Poly(vinyl butyral)


Ricinoleic acid



We very much appreciate the financial support from the Deutsche Forschungsgesellschaft (DFG) by grant PE1160/7-1.

Supplementary material

11051_2012_990_MOESM1_ESM.doc (317 kb)
Supplementary material 1 (DOC 316 kb)


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  1. 1.Helmholtz-Institute Freiberg for Resource TechnologyFreibergGermany
  2. 2.TU Bergakademie Freiberg, Institute of Mechanical Process Engineering and Minerals ProcessingFreibergGermany

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