Preparation of micrometer-sized poly(methyl methacrylate) particles with amphoteric initiator in aqueous media

Shunchao Gu, Hiromitsu Akama, Daisuke Nagao, Yoshio Kobayashi, Mikio Konno

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


A previously proposed method based on soap-free emulsion polymerization with an amphoteric initiator for producing micrometer-sized polystyrene particles was extended to application with methyl methacrylate (MMA). The aggregation and dispersion stability of polymer particles, which have ionizable groups arising from initiator radicals, can be controlled by adjusting the pH of the reaction system accompanied with the addition of ionic monomer. Polymerizations were carried out with 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate amphoteric initiator, NH3/NH4Cl pH buffer, and sodium p-styrenesulfonate anionic monomer (NaSS) in ranges of MMA concentration (0.58-2.32 kmol/m3 H2O) and NH3 concentration (2.5-20 mol/m3 H2O) at fixed concentrations of 5 mol/m3 H2O initiator, 10 mol/m3 H2O NH4Cl, and 1 mol/m3 H2O NaSS at 65 °C. The addition of NaSS during the polymerization could improve stability in dispersion of particles, which coagulated in the absence of NaSS after the disappearance of monomer drops. An increase in the monomer concentration in the present method could enlarge the particle size without lowering the monodispersity of the particle size distribution. On the other hand, an increase in NH3 concentration decreased the particle size. The highest monodispersity of particle sizes was obtained at a NH3 concentration of 5 mol/m3 H2O, which gave an average size of 1.5 μm and a coefficient of variation of particle size distribution of 2.2% that was much smaller than the standard criterion for monodispersity, 10%.

Original languageEnglish
Pages (from-to)7948-7951
Number of pages4
Issue number19
Publication statusPublished - 2004 Sep 14

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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