• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1891-1896
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• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• Macromolecular Research
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• v.11 no.2
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• pp.104-109
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• 2003

A microcellular, which combines a rubber with the conventional formulation of styrene/divinylbenzene/sorbitan monooleate/water system, was prepared using high internal phase emulsion (HIPE) polymerization. Although the open microcellular foam with low density from the conventional HIPE polymerization shows highly porous characteristics with fine, regular and isotropic structure, the one having much smaller cell size is desirable for various applications. In this study, a polybutadiene was introduced to reduce the cell size with comparable properties. Major interests were focused on the effects of rubber concentration and agitation speed on the cell sizes and compression properties. Scanning electron microscopy was used to observe the microcellular morphology and compression tests were conducted to evaluate the stress-strain behaviors. It was found that the cell size decreased as rubber concentration increased, reflecting a competition between the higher viscosity of continuous phase and the lower viscosity ratio of dispersed to continuous phases due to the addition of high molecular weight rubber into the oil phase of emulsion. A correlation for the average cell size depending on agitation speed was attempted and the result was quite satisfactory.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.10b
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• pp.41-44
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• 1999

• KSBB Journal
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• v.31 no.4
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• pp.256-262
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• 2016

The need for natural cosmetic ingredients has been increasing over the world nowadays. Agarose, a natural polymer from red seaweeds, has high hydrophilic character and a function of scaffolder. As skin moisturizer, agarose is adequate for percutaneous absorption. While, blueberry fruits extract possesses rich procyanidins and anthocyanins which show health benefits, anti-oxidant effect, anti-aging and anti-melanogenesis. Stability, sensory preference, skin trouble of the emulsion formula are important for cosmetic product development. In this study, we manufactured an emulsion formula for skin moisturizers using the two ingredients and tested emulsion stability and skin trouble. Total phenolic contents of the blueberry fruits extract were evaluated as well as tyrosinase inhibitory and collagenase inhibitory activities. $IC_{50}$ values of blueberry fruits extract for anti-tyrosinase and anti-collagenase activities were 168 and $112{\mu}g/mL$, respectively using gallic acid as a control ($64.8{\mu}g/mL$). The stability (pH and viscosity) of the formula containing 2% blueberry fruits extracts and 0.1% agarose was measured at five different temperatures (room temp., $25^{\circ}C$, $55^{\circ}C$, $45^{\circ}C$, $55^{\circ}C$) under the sun light at 2 day intervals for 12 days. There has been little pH change at the different temperatures. According to the sensory evaluation, there was no significant flavor, discoloration and physical changes of the formula at $25-65^{\circ}C$. These results suggest that emulsion formula containing blueberry extract and agarose could be used as a candidate for lotion and essence products.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.758-762
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• 1998

In preparing void latex particles by emulsion polymerization, the weight mean particle size of which is ranged $0.3{\mu}m{\sim}1.5{\mu}m$, reaction parameters were investigated in order to elucidate their effects on the size distribution and the solid content of emulsion polymer. Experimental results showed that the weight mean particle size of hydrophillic core polymer was reduced as the concentration of sodium dodecylbenzene sulfonate (SDS) increased. The size of void polymethyl-methacrylate-polystyrene composite latex particles became larger as the concentration of styrene monomer and the sodium persulfate increased. However, the size of void latex particles was reduced as the feeding rate of acrylic acid increased. The solid content of emulsion polymer was strongly dependent on the addition of stylene monomer. By increasing the concentration of styrene monomer the solid content of emulsion polymer increased linearly.

• Polymer Science and Technology
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• v.7 no.4
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• pp.412-424
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• 1996

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.300-305
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• 1998

Kinetics of termonomer emulsion polymerization during interval II (i.e, after completion of latex particle formation) were studied through pseudo-homopolymerization (PHP) method. Extended Smith-Ewart equation and equation of instantaneous polymer composition are respectively reduced to the corresponding equation for homopolymerization by defining average rate constants. Average number of radicals per particle and instantaneous polymer compositions were respectively predicted by varying termonomer composition within latex particles for systems containing no more than one growing radical per particle. Styrene-Methyl methacrylate-Acrylonitrile (SMA) system was used for model calculation.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.289-289
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• 2006

The carboxylated MWNTs were successfully prepared by conventional acid treatment, and their structures were confirmed by FT-IR, Raman and TEM analysis. The water-dispersibility of the surface modified WNTs were good. The COOH-MWNT will show better stability during the emulsion polymerization as compared with Pristine MWNT. In-situ emulsion polymerizations of methyl methacrylate N(MMA) and n-butyl acrylate (BA) were carried out. Aggregate size and dispersion stability of the CNTs in water phase were measured using dynamic light scattering, turbidity, UV-visible spectrophotometer, and electron microscope. In addition, thermo-mechanical properties of MWNT/polymer nanocomposites were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.400-401
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• 2008

전기영동형 전자종이 디스플레이의 새로운 소재로써 $C_{60}$(fullerene)와 같은 나노 입자를 포함하는 새로운 전기영동 입자를 제조하였다. 본 연구에서는 안정제로 poly(vinyl pyrrolidone)(PVP)를 사용하여 fullerene을 포함하는 styrene emulsion을 안정화 한 후 라디칼 중합을 통해 fullerene이 포함된 polystyrene microemulsion particles을 제조 합으로써 입자의 분산안정성을 높이고 전기영동에 따른 입자의 움직임을 최적화하도록 하였다. 이 실험에서는 fullerene의 양에 따라 제조된 입자의 크기와 입자 분포를 관찰하였다. 입자의 크기와 입자 분포는 주사형 전자현미경 (SEM) 을 이용하여 확인하였다. 또한 fullerene-PS 입자의 구조 분석과 특성평가를 위해서 FT-IR를 측정하였고, 입자의 열적 성질을 위해 TGA를 측정하였다.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.159-166
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• 2012

We have introduced the Pickering emulsion systems to generate novel confining geometries for the selforganization of monodisperse polymer microspheres using nanoparticle-stabilized emulsion droplets encapsulating the building block particles. Then, through the slow evaporation of emulsion phases by heating, these microspheres were packed into regular polyhedral colloidal clusters covered with nanoparticle-stabilizers made of silica. Furthermore, polymer composite colloidal clusters were burnt out leaving nonspherical hollow micro-particles, in which the configurations of the cluster structure were preserved during calcination. The selfassembled porous architectures in this study will be potentially useful in various applications such as novel building block particles or supporting materials for catalysis or gas adsorption.