title: Preparation of micrometer-sized poly(methyl methacrylate) particles with amphoteric initiator in aqueous media.
abstract: 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, NH(3)/NH(4)Cl pH buffer, and sodium p-styrenesulfonate anionic monomer (NaSS) in ranges of MMA concentration (0.58-2.32 kmol/m(3) H(2)O) and NH(3) concentration (2.5-20 mol/m(3) H(2)O) at fixed concentrations of 5 mol/m(3) H(2)O initiator, 10 mol/m(3) H(2)O NH(4)Cl, and 1 mol/m(3) H(2)O NaSS at 65 degrees 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 NH(3) concentration decreased the particle size. The highest monodispersity of particle sizes was obtained at a NH(3) concentration of 5 mol/m(3) H(2)O, which gave an average size of 1.5 microm and a coefficient of variation of particle size distribution of 2.2% that was much smaller than the standard criterion for monodispersity, 10%.
authors.affiliation: Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, Aoba, Aramaki-aza, Aoba-ku, Sendai, 980-8579, Japan.
authors.forename: Shunchao
authors.initials: S
authors.lastname: Gu
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Akama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nagao
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Mikio
authors.initials: M
authors.lastname: Konno
mesh_terms: D000577:Amides / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000138:chemical synthesis* / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: C510810:2,2'-azobis(N-(2-carboxyethyl)-2-methylpropionamidine) tetrahydrate; D000577:Amides; D001391:Azo Compounds; D011108:Polymers; D013451:Sulfonic Acids; D014867:Water; D019904:Polymethyl Methacrylate; C077114:styrenesulfonic acid polymer