title: Novel mini-reactor of silicone oil droplets for synthesis of morphology-controlled polymer particles.
abstract: Inside spaces of emulsion droplets can be used as mini-reactors for material synthesis. The novel application of sol-gel derived silicone oil droplets as mini-reactors was examined for the case of polymerization of styrene (St) and comonomers with the oil-soluble initiator 2,2'-azobis(2,4-dimethylvaleronitrile). Polydimethylsiloxane (PDMS) droplets prepared from dimethylsiloxane were used as the mini-reactors, in which the polymerization of St without comonomers was first conducted. In the polymerization, the St/PDMS volume ratio was varied from 0.025 to 0.10. After the polymerization, each PDMS droplet contained a polystyrene (PSt) particle. The St/PDMS ratio of 0.05 enabled the synthesis of micrometer-sized, spherical PSt particles with low polydispsersity. Copolymerization of St with comonomers having hydrophilic groups deformed the spherical shape of particles to lens-like or disk-like morphologies that were obtained with acrylic acid or sodium 4-styrene sulfonate, respectively. In another copolymerization, with divinylbenzene used as a cross-linker, hemispherical polymer particles were formed. To diversify the particle morphologies further, the proposed mini-reactor synthesis was combined with the recently proposed silicone oil droplet templating method (Ohta et al., 2012). Around the PDMS droplets containing a polymer particle, polymeric shells with a depression were successfully formed with the proposed method. The remaining PDMS oil inside the polymeric shells was extracted with ethanol, which caused hemispherical polymeric bowl-shaped capsules having a protrusion on the inside.
authors.affiliation: Department of Chemical Engineering, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Sendai, 980-8579, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nagao
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ohta
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Ishii
authors.forename: Arnout
authors.initials: A
authors.lastname: Imhof
authors.forename: Mikio
authors.initials: M
authors.lastname: Konno