title: Colloidal stability of iron oxide nanoparticles with multivalent polymer surfactants.
abstract: This paper introduces a new approach for preparing magnetic colloidal suspensions with electrostatic repulsion between particles and polyelectrolyte surfactants. The surface charge of the iron oxide particles was positive in acidic aqueous conditions; however the surface charge of the colloid was negative in basic aqueous conditions due to the amphoteric property of Fe2O3. The long-term colloidal stability and particle distribution of the multivalent charged polymers, Poly(4-vinylbenzenesulfonate sodium salt) (PSS), Poly(acrylic acid) (PAA), and Poly(allylamine hydrochloride) (PAH) were compared with the monovalent surfactant sodium dodecyl sulfate (SDS). Both mono- and multivalent surfactant molecules showed good colloidal stability for extended periods of time. However, the particle distribution was dependent on the hydrophobicity of the surfactants' functional groups. Polyelectrolytes with a negatively charged functional group showed good long-term stability of particles and a narrow particle distribution regardless of the acid dissociation constant (pKa) of the polymer.
authors.affiliation: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea; Department of Chemical Engineering and Material Science, University of California, Irvine 92607, USA. Electronic address: yochoi92@hanmail.net.
authors.forename: Young-Wook
authors.initials: YW
authors.lastname: Choi
authors.affiliation: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea.
authors.forename: Hoik
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea.
authors.forename: Youngjun
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea. Electronic address: dsohn@hanyang.ac.kr.
authors.forename: Daewon
authors.initials: D
authors.lastname: Sohn
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D011108:Polymers / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D055672:Static Electricity; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D003102:Colloids; D004573:Electrolytes; D005290:Ferric Compounds; D011108:Polymers; D013501:Surface-Active Agents; C000499:ferric oxide; D012967:Sodium Dodecyl Sulfate
keywords: Colloidal stability; Iron oxide; Magnetic particle; Polyelectrolyte; Polymer surfactant