Faculty Publications
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Item Synthesis of poly(styrene-co-methyl methacrylate) nanospheres by ultrasound-mediated Pickering nanoemulsion polymerization(Springer Netherlands rbk@louisiana.edu, 2019) Buruga, K.; Kalathi, J.T.Poly (styrene-co-methyl methacrylate) (PS-co-PMMA) nanospheres were synthesized by ultrasound-mediated Pickering nanoemulsion polymerization using halloysite nanotubes (HNTs) as a stabilizer. A relatively high conversion (? 99%) was obtained in a short span of time (60 min) relative to (?97%) for that obtained by conventional emulsion polymerization performed without ultrasound. The initial rate of polymerization and the conversion were found to be increasing with the acoustic intensity in the range of 12.5–25 W/cm2). The synthesized copolymer nanosphere particles exhibited a perfect spherical shape (from TEM analysis), good stability (from zeta-potential analysis), high molecular weight (Mw? 311 kDa from Gel permeation chromatography), and excellent thermal properties (Tg? 120°C from DSC and TGA) as a result of the combined physicochemical effects of acoustic cavitation. The formation of nanosized emulsion droplets stabilized by HNTs ultimately yielded nanospheres of PS-co-PMMA with an average size of ? 82.8 nm. The PS-co-PMMA nanospheres can have potential applications in medicine, dentistry, paper, paint, and automotive industries. © 2019, The Polymer Society, Taipei.Item Interface Dominated Dielectric Response of PS-Fe3O4 Patchy Microspheres(American Chemical Society service@acs.org, 2019) Kishor Kumar, M.J.; Kalathi, J.T.Polymeric-inorganic interface plays a vital role in enhancing dielectric properties of patchy microspheres, Janus particles, and nanocomposites. We performed the computational modeling and simulations along with experiments to understand the phenomena behind the improved dielectric permittivity of polystyrene-iron oxide (PS-Fe3O4) patchy microspheres. We addressed the fundamental insights into the role of the interfacial region on the dielectric properties. Based on the experimental outcomes and computational simulations on dielectric behavior including polarization and electric field formation, we propose a new mechanism of charge buildup at the interface. Computational results reveal that the creation of interface bound-charges at the inorganic-polymeric interface is responsible for the improved dielectric properties. We also fabricated PS-Fe3O4 patchy microspheres by Pickering emulsion polymerization using Fe3O4 particles as a solid stabilizer. The microstructure, composition, morphology, dielectric, and thermal properties of the synthesized patchy PS-Fe3O4 particles were investigated. The dielectric permittivity (k) of the neat PS increased from ?2.9 to ?14.8 after decorating with Fe3O4 particles. Impedance response of the patchy microspheres shows that the interface of PS-Fe3O4 stores more charges than bulk PS-Fe3O4. The dielectric behavior of patchy microspheres can be engineered by tuning the shape and position of the patches. The present studies on polymer-inorganic interface provide some insights into the mechanisms that control dielectric permittivity and nonlinear conduction in an applied electric field. © © 2019 American Chemical Society.