Soap-free synthesis of highly monodisperse magnetic polymer particles with amphoteric initiator

Noriko Yamauchi, Daisuke Nagao, Mikio Konno

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


A method applying soap-free emulsion polymerization with an amphoteric initiator, 2,2′-azobis[N-(2-carboxyethyl)-2-2-methyl-propionamidine], is proposed for synthesis of highly monodisperse particles composed of magnetic nanoparticles (Fe3O4/γ-Fe2O3) and polystyrene. The magnetic nanoparticles were pretreated by surface modification for introducing double bonds onto the particles. In the polymerization, magnetic nanoparticles were continuously supplied to the system for a certain period after the initiation of polymerization at various pH. Dissociation degrees of ionizable groups in the initiator molecules were controlled through pH by changing NH3 concentrations at a constant NH4Cl concentration. Selection of suitable pH in the polymerization could produce polymer particles that perfectly incorporated the supplied magnetic nanoparticles. The magnetic polymer particles had a coefficient of variation of size distribution as low as 4.3% with an average diameter of 515 nm and a saturation magnetization of 7.3 emu/g-sample. Electrophoresis measurements indicated that the magnetic polymer particles had an isoelectric point of pH 4.1.

Original languageEnglish
Pages (from-to)55-61
Number of pages7
JournalColloid and Polymer Science
Issue number1
Publication statusPublished - 2010 Jan


  • Amphoteric
  • Magnetic polymer particle
  • Monodisperse
  • Soap-free emulsion polymerization

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Colloid and Surface Chemistry
  • Materials Chemistry


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