title: Preparation and colloidal stability of monodisperse magnetic polymer particles.
abstract: A previously proposed method was examined for producing monodisperse, submicrometer-sized magnetic polymer particles. The method applies soap-free emulsion polymerization during which Fe3O4 magnetic nanoparticles are heterocoagulated onto precipitated polymer nuclei. To chemically fix the magnetic particles to the polymer nuclei, vinyl groups were introduced on the Fe3O4 particles in a preliminary surface modification reaction with methacryloxypropyltrimethoxysilane, and methacryloxypropyldimethoxysilane (MPDMS) was added to reaction systems of the soap-free emulsion polymerization. The colloidal dispersion stability of magnetic polymer particles was improved by the addition of an ionic monomer, sodium p-styrenesulfonate (NaSS), during the polymerization. The polymerizations were carried out with styrene monomer and potassium persulfate initiator in ranges of NaSS concentrations (0-2.4 x 10(-3) M), NaSS addition times (60-80 min), and monomer concentrations (0.3-0.6 M) at fixed concentrations of 1.6 x 10(-2) M initiator and 1.3 x 10(-2) M MPDMS for pH 4.5 adjusted with a buffer system of [CH3COOH]/[NaOH]. The addition of NaSS during the polymerization could maintain the dispersion stability of magnetic polymer particles during the polymerization. Selection of the reaction conditions enabled the preparation of colloidally stable, submicrometer-sized magnetic polymer particles that had coefficients of variation of distribution smaller than the standard criterion for monodispersity, 10%.
authors.affiliation: Department of Chemical Engineering, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
authors.forename: Shunchao
authors.initials: S
authors.lastname: Gu
authors.forename: Junya
authors.initials: J
authors.lastname: Onishi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nagao
authors.forename: Mikio
authors.initials: M
authors.lastname: Konno
mesh_terms: D003102:Colloids; D004655:Emulsions; D052203:Ferrosoferric Oxide / Q000138:chemical synthesis / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003102:Colloids; D004655:Emulsions; D011108:Polymers; D052203:Ferrosoferric Oxide