Hak-Hee Kang

Zinc oxide/polymethylmethacrylate composite microspheres by in situ suspension polymerization and their morphological study

Homogenously zinc oxide (ZnO)-dispersed polymethylmethacrylate (PMMA) composite microspheres were produced considering the interfacial characteristics of ZnO and PMMA in in situ suspension polymerization. The morphological observation with electron microscopes revealed that nano-sized ZnO particles were embedded homogeneously in the inner part of PMMA microspheres. Moreover, their spherical shape could be maintained to a large amount of ZnO in the PMMA phase. From this study, it was found that one of key requirements in the synthesis of inorganic/polymer composite microspheres was the enhanced interfacial compatibility between inorganic and polymer, which was achieved by treating the surface of inorganics hydrophobically and imparting conformational anchorage factor at inorganic interfaces.

Effective Formation of Silicone-in-Fluorocarbon-in-Water Double Emulsions: Studies on Droplet Morphology and Stability

ABSTRACT Silicone-in-fluorocarbon-in-water double emulsions were prepared by controlling carefully the characteristics of the emulsions composed of silicone, perfluoropoly-ethoxymethoxy difluorohydroxyethyl ether (PFPE–OH) and fluorosurfactant. In the emulsion formulation, PFPE–OH incorporated had a great influence on the droplet morphology and the stability of double emulsions. Moreover, it was observed that among the fluorocarbons, the silicone-in-fluorocarbon-in-water double emulsions could be formed effectively in the presence of a fluorosurfactant. The double emulsions prepared in this study maintained their initial emulsion stability for a long time at high temperature, meaning great usefulness in the cosmetic industry.

Stabilization of Water‐Soluble Antioxidant in Water‐in‐Oil‐in‐Water Double Emulsions

Abstract In this study, we are introducing a method that can effectively stabilize antioxidants in water‐in‐oil‐in‐water (W/O/W) double emulsions. Preliminarily, stable W/O/W double emulsions were produced by manipulating the characteristics of internal aqueous phase via two‐stage emulsification, resulting consequently in the formation of fine internal water droplets in the dispersed oil droplets. From conductivity measurements that can determine the elution amount of internal aqueous phase, it was confirmed that the double emulsion stability could be improved by treating the internal aqueous phase with a hydroxypropyl‐beta‐cyclodextrin. In this study, kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4‐pyrone was selected as a model antioxidant. The stabilization of kojic acid was attempted by locating it in the internal water droplets of the stable W/O/W double emulsions. The stability of kojic acid in the double emulsion system could be maintained at 90% for 10 weeks at high temperature. We believe that these stable W/O/W double emulsions could be used meaningfully as a carrier for many unstable antioxidants.

Determination of antioxidant and α-glucosidase inhibitory activities and luteolin contents of Chrysanthemum morifolium Ramat extracts

Antioxidant and α-glucosidase inhibitory activities as well as luteolin contents were analysed in extracts of Chrysanthemum morifolium Ramat (CM), which is a traditional medicinal plant and an important oriental herbal medicine for the treatment of eye diseases in China and Japan. In this study, the results show that the maximum solvent extract yield (35.5%) and luteolin concentration (1.34 �g/ml) were achieved in methanol extract. In addition, 60% methanol extracts of CM exhibited high scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as significant reducing power. They also possessed a potent α-glucosidase inhibitory activity. Furthermore, the total phenolic content was 0.37 mg GAE/g. The total phenolic content of 60% methanol extract may have been the cause of its strong antioxidant ability. These results provide scientific support that the food industry could benefit from using extract containing this constituent.

Emulsion properties of pseudo-ceramide PC104/water/polyoxyethylene cholesteryl ether and polyoxyethylene cetyl ether mixtures

Abstract The formation of emulsions and micelles in water/ceramide PC104/CholEO 20 /C 16 EO 20 and water/ceramide PC104/CholEO 20 mixtures was investigated through the phase behavior studies. The phase diagrams showed the existence of micelle and emulsion regions in both systems. The mixed surfactant system (CholEO 20 /C 16 EO 20 ) showed the wider micellar and emulsion regions than the single surfactant system (CholEO 20 ). From FT-IR measurements, it was found that the polyoxyethylene (POE) groups of surfactants formed the hydrogen bonds with amido carbonyl group in ceramide PC104. This result indicated that the hydrophilic part (EO) of surfactants could stabilize the lamellar structure and emulsion of ceramide PC104. The mixed surfactant system (CholEO 20 /C 16 EO 20 ) resulted in the smaller emulsion droplet size due to the effect of curvature at the interface, thus further increasing emulsion stability. With the penetration of C 16 EO 20 into the interfacial layer of surfactants in emulsion, the curvature of the interface might be altered for the formation of smaller emulsion droplets. The mixed surfactant system could incorporate up to 4 wt.% of ceramide PC104 into emulsion more than single surfactant system.