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

Abstract

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.

Magnetic Properties of Ni/NiO Nanowires Deposited onto CNT/Pt Nanocomposites

“…For complex magnetic materials that comprise ferromagnetic and antiferromagnetic components, a careful characterization in terms of crystalline structure, magnetization, axial and unidirectional magnetic anisotropy, superparamagnetism, and the exchange-bias effect is required. Several methods have been exploited for the synthesis of these magnetic colloids while controlling the magnetic anisotropy: relatively simple variations in surfactant composition to selectively control the growth rates of different faces; [1] similar procedures to those concerning semiconductor materials; [5,6] assembling previously synthesized magnetic nanoparticles as chains or necklaces; [2][3][4][7][8][9][10][11][12] exploiting electrostatic interactions between the surface charge of magnetic nanoparticles and previously modified carbon nanotubes (CNTs); [13] and depositing the magnetic material on the surface of CNTs in a step-by-step procedure, leading to homogeneous outer shells. To investigate the possibility of obtaining nanowires with a very narrow size distribution and without chemical bonding at the surface we have chosen this fourth option.…”

Structure and Properties of Iron Oxide Nanoparticles Encapsulated by Phospholipids with Poly(ethylene glycol) Tails

“…Poly(ethylene glycol) (PEG) containing shells are proven to be biocompatible, well soluble in water, and suitable for biomedical applications. 10,22,23 The shell on the NP surface can be created using several methods: by adsorption or growth of polymer or block copolymer chains, 22,24 by formation of NPs in the presence ofpolymericsurfactants, 25 byattachmentoffunctionalligands, 23,[26][27][28] or by formation of hydrophobic bilayers of amphiphilic molecules with the hydrophobic NP coating (encapsulation into amphiphilic micelles). [29][30][31] In this article, we report structure and properties of iron oxide NPs synthesized by decomposition of iron oleates and coated with PEGylated phospholipids via encapsulation.…”

Functionalization of nanoparticles for dispersion in polymers and assembly in fluids

“…53,54 For CdSe quantum dots, this grafting-to approach has been applied by Bawendi et al 55 using polynorbornene with pendant alkylphosphines and by Scholes et al 56 using poly(dimethylaminoethyl methacrylate). The multivalency of these functional polymers provides numerous ligand/quantum-dot interactions per polymer chain, promoting stabilization of the quantum dots against aggregation.…”