Novel Mini-Reactor of Silicone Oil Droplets for Synthesis of Morphology-Controlled Polymer Particles

• Published in: Langmuir Vol. 28; no. 51; pp. 17642 - 17646
• Main Authors: Nagao, Daisuke, Ohta, Tatsuya, Ishii, Haruyuki, Imhof, Arnout, Konno, Mikio
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 21.12.2012
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Spherical shape; Acrylic acid; Alcohol; Copolymerization; Sulfonate; Template; Particle; Emulsion; Synthesis; Alkanol; Styrene polymer; Reactor; Disk; Ethanol; Silicone oil; Polymerization; Polymer; Capsule; Droplet; Protrusion; Sol gel process; Morphology; Micrometer; Lens; Spherical particle
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la304348g

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.