• Macromolecular Research
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• v.17 no.6
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• pp.397-402
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• 2009

In emulsifier-free, emulsion polymerization with ionizable comonomer, the ionization of the comonomer is critical in determining the size of the final polymerie particles at sub-micrometer scale. In this study, polystyrene latex beads with carboxylates on the surface were synthesized using acrylic acid as a comonomer. Specifically, ammonium hydroxide was added to the emulsifier-free polymerization system to promote the ionization of acrylic acid by increasing pH. Smaller polystyrene latex particles were produced by increasing the ammonium hydroxide concentration in the reaction system, due to the enhanced stability promoted by the ionization of acrylic acid during the nucleation step. In addition, the surface morphology of the polystyrene latex particles was controlled by the concentration of acrylic acid, the dissociation of which was influenced by the ammonium hydroxide concentration.

• Polymer(Korea)
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• v.34 no.6
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• pp.491-494
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• 2010

Colored, electrophoretic polymer nanoparticles of poly (styrene-co-divinylbenzene-co-vinyl acetate)[poly(St-co-DVB-co-VAc)] were prepared by emulsifier-free emulsion co-polymerization and reactive dyeing. The emulsifier-free emulsion polymerization of styrene, divinyl benzene and vinyl acetate was carried out at $70^{\circ}C$ for 20 hrs to obtain monodisperse polymer nanoparticles of poly(St-co-DVB-co-VAc) with an average diameter of 180~200 nm. These nanoparticles were transformed into poly(styrene-co-divinylbenzene-co-vinyl alcohol) [poly(St-co-DVB-co-VA)] nanoparticles through the saponification reaction. The poly(St-co-DVB-co-VA) nanoparticles were treated with reactive dyes to obtain the colored, monodisperse electrophoretic nanoparticles, and their morphology and surface charge were characterized by scanning electron microscopy, differential scanning calorimetry, UV/Vis absorbance and zeta-potentiometry.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.995-997
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• 2003

In this study, we have investigated the positively charged polymer particles using emulsifier-free emulsion polymerization for applications in electrophoretic displays. The FT-IR, Zeta potential and SEM characteristics showed that by emulsifier-free polymerization, the positively charged polymer particles were manufactured. Using these particles, we can obtain well-dispersed white latex particles in dielectric suspending media.

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.185-191
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• 2009

Polystyrene/multi-walled carbon nanotube (PS/MWCNT) composites were prepared by the use of latex technology. The monodisperse PS latex was synthesized by an emulsifier-free emulsion polymerization from styrene/potassium persulfate/water system in the presence of ethanol. The MWCNTs were first treated with acid mixture to eliminate impurities, dispersed in deionized water driven by ultrasonicator, and then mixed with the PS latex. From these mixtures, PS/MWCNT composites were prepared by freeze-drying and subsequent compression molding. In the small-amplitude oscillatory shear experiments, both complex viscosity and storage modulus increased with increasing MWCNT content. A pronounced effect of MWCNT content was observed, resulting in larger storage modulus and stronger yield behavior at low frequencies when compared to unmodified PS. It showed a transition from viscous to elastic behavior with increasing MWCNT content. Over the MWCNT content of 3 wt%, the storage modulus was higher than the loss modulus across all frequencies.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.999-1005
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• 2007

An oil-in-water (O/W) emulsion [20 wt% com oil, 0.5-6.0 wt% fish gelatin (FG), pH 3.0] was produced by high pressure homogenization, and the influence of pH, protein concentration, and homogenization condition on the formation of FG-stabilized emulsions was assessed by measuring particle size distribution, electrical charge, creaming stability, microstructure, and free FG concentration in the emulsions. Optical microscopy indicated that there were some large droplets ($d>10\;{\mu}m$) in all FG-emulsions, nevertheless, the amount of large droplets tended to decrease with increasing FG concentration. More than 90% of FG was present free in the continuous phase of the emulsions. To facilitate droplet disruption and prevent droplet coalescence within the homogenizer, homogenization time was adjusted in O/W emulsions stabilized by 2.0 or 4.0 wt% FG. However, the increase in the number of pass rather promoted droplet coalescence. This study has shown that the FG may have some limited use as a protein emulsifier in O/W emulsions.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.7-14
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• 1993

Nowadays, microspheres are expected to be applied to biomedical areas and many studies are being performed. For biomedical applications, many kinds of microspheres were synthesized by emulsion polymerization, emulsifier-free emu]sion polymerization, and emulsifier-free emulsion polymerization with ionic surface-active comonomers. Further synthesis techniques about microencapsulation and magnetic microspheres are introduced. Among the practical applications of microspheres, some interesting subjects are introduced. These include solid-phase immunoassays, labeling and identification of lymphocyte populations, extracorporeal and hemoperfusion systems, drug delivery systems, and immunomagnetic cell separation. In addition, basic theories, problems and research trends are also introduced.

• Polymer(Korea)
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• v.28 no.6
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• pp.524-530
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• 2004

Polystyrene particles (PS) with poly(ethylene glycol) units on surface were formed by an emulsifier-free emulsion polymerization using styrene, poly(ethylene glycol) methacrylate (PEG-MMA) or poly(ethylene glycol) dimethacrylate (PEG-diMMA) at pH 7, and followed by freeze-drying to give the corresponding powders. The structures of PS particles were confirmed by FT-IR spectroscopy, and the particle size and distribution the PS particle were observed by scanning electron microscopy and particle analyzer. Monodisperse polymer particles were obtained at a concentration of PEG-MMA 2∼5 mol% or PEG-diMMA 1 mol% relative to styrene. The highest zeta potential of polymer surface was measured to be 183 mV at a polymer of PEG-MMA 5 mol%, which was measured in dielectric medium by means of ELS-8000 dynamic light scattering.

• Macromolecular Research
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• v.14 no.2
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• pp.194-198
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• 2006

Polystyrene, PS, particles of 450 nm diameter and poly(styrene-co-styrene sulfonate), PSS, particles of 140-160 nm diameter were prepared by emulsifier-free emulsion polymerization. The surfaces of the PS and PSS particles were coated with Ag nanoparticles for the application of antimicrobial agents by reduction of Ag ions using ${\gamma}$-irradiation. The Ag-PS and Ag-PSS were characterized by High-Resolution Transmittance Electron Microscopy (HR-TEM), Field-Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive X-ray Spectroscopy (EDXS). The HR-TEM and EDXS data showed that the Ag nanoparticles were loaded on the surface of the PS and PSS particles, respectively. The antimicrobial efficiency of the Ag-PS and Ag-PSS particles (0.4 g) with ca. 100 ppm Ag, which was coated onto yam (KS K 0905-1996 rule), was tested against Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352 after 100 washing cycles (KS K 0432-1999 rule). The antimicrobial efficiency of the Ag-PS particles against Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352 was 99.9% after 100 cycles washing., confirming that the Ag-PS particles can be used as antimicrobial agents.

• Elastomers and Composites
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• v.54 no.4
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• pp.335-344
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• 2019

In this work, styrene butadiene rubber (SBR) and styrene butadiene styrene (SBS) were used to modify asphalt, resulting in SBR- and SBS-modified asphalt, respectively. The two modified asphalts were emulsified with a nonionic emulsifier (Span 60) and cationic emulsifiers (ID, DDA) and their phase stabilization was investigated via particle size, Zeta potential, and flow behavior analysis. With increasing amount of the mixed emulsifier, the particle size decreased, leading to an increase in viscosity. The shear thinning behaviors and Zeta potential values ranging from 35-65 mV were determined and remained considerably stable. In addition, the adhesion strength and compression strength of the SBR-and SBS-modified asphalt emulsion were evaluated via surface free energy examination. The remarkable adhesion and compression strengths were estimated when 5 phr ID and 6 phr DDA were added to the emulsified asphalt modified with SBR and SBS. Therefore ID and DDA, the two cationic surfactants, played significant roles in improving the dispersion and interfacial adhesion strength, resulting in the improved adhesion and compression strength of the emulsified asphalts modified with SBR and SBS.

• Journal of the Korean Applied Science and Technology
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• v.25 no.3
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• pp.275-281
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• 2008

The esterification of free fatty acid in Jatropha oil added by propylene glycol using p-TSA catalyst was done, and then the transesterification of Jatropha oil added by 1.0vol% GMS as an emulsifier using TMAH, and mixed catalyst(60wt%-TMAH+ 40wt%-KOH) respectively was followed at $60^{\circ}C$. The esterification conversion at the 1:8 molar ratio of free fatty acid to methanol using 8.0wt% p-TSA was 94.7% within 60min. The overall conversion at the 1:8 molar ratio of Jatropha oil to methanol and $60^{\circ}C$ using mixed catalyst was 95.4%. The kinematic viscosity of Biodiesel using TMAH and mixed catalyst in 24h met the ASTM D-6751 above $30^{\circ}C$, and showed a little more than its criterion.