Soap-free synthesis of highly monodisperse magnetic polymer particles with amphoteric initiator |
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Authors: | Noriko Yamauchi Daisuke Nagao Mikio Konno |
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Affiliation: | (1) Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6-6-07, Aoba, Aramaki-aza, Aoba-ku, Sendai 980-8579, Japan; |
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Abstract: | 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. |
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