title: Synthesis and self-assembly of polymer-coated ferromagnetic nanoparticles.
abstract: We describe the synthesis and characterization of polymer-coated ferromagnetic cobalt nanoparticles (CoNPs). The synthesis of end-functionalized polystyrene surfactants possessing amine, carboxylic acid, or phosphine oxide end-groups was accomplished using atom-transfer radical polymerization. This versatile synthetic method enabled the production of multigram quantities of these polymeric surfactants that stabilized ferromagnetic CoNPs when dispersed in organic media. An in-depth investigation into the synthesis of polystyrene-coated ferromagnetic CoNPs was also conducted using various combinations of these polymeric surfactants in the thermolysis of dicobaltoctacarbonyl (Co(2)(CO)(8)). Moreover, the application of a dual-stage thermolysis with Co(2)(CO)(8) allowed for the preparation of large samples (200-820 mg) per batch of well-defined and dispersable ferromagnetic nanoparticles. Characterization of these functionalized nanoparticle materials was then done using transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis. Self-assembly of these dipolar nanoparticles was investigated in solutions cast onto supporting substrates, where local nematic-like ordering of nanoparticle chains was observed along with a tendency of adjacent chains to form "zippering" configurations, both phenomena having been predicted by recent simulations of dipolar fluids in conjunction with van der Waals interactions.
authors.affiliation: Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Pei Yuin
authors.initials: PY
authors.lastname: Keng
authors.forename: Inbo
authors.initials: I
authors.lastname: Shim
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Korth
authors.forename: Jack F
authors.initials: JF
authors.lastname: Douglas
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Pyun