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Polymer-Coated Ferromagnetic Colloids from Well-Defined Macromolecular Surfactants and Assembly into Nanoparticle Chains

2006; American Chemical Society; Volume: 128; Issue: 20 Linguagem: Inglês

10.1021/ja0609147

1943-2984

Bryan D. Korth, Pei Yuin Keng, In‐Bo Shim, Steven E. Bowles, Chuanbing Tang, Tomasz Kowalewski, Kenneth W. Nebesny, Jeffrey Pyun,

Surfactants and Colloidal Systems

A novel synthetic route to polymer-coated ferromagnetic colloids of metallic cobalt has been developed. Well-defined end-functional polystyrenes were synthesized using controlled radical polymerization and used as surfactants in the thermolysis of dicobaltoctacarbonyl to afford uniform ferromagnetic nanoparticles. The presence of the polymer shell enabled prolonged colloidal stability of dispersions in a wide range of organic solvents and formed glassy encapsulating coatings around ferromagnetic cores in the solid state. These polymer-coated colloids assembled into robust, micron-sized nanoparticle chains when cast onto supporting surfaces due to dipolar associations of magnetic cores. Hierarchical assemblies were also prepared by blending polystyrene-coated cobalt colloids with larger silica beads.