• Title/Summary/Keyword: microemulsions

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Kinetics of Structural Transitions in Surfactant Solution (계면활성제 수용액에 있어 구조변화에 따른 동력학적 고찰)

  • Nam, Ki-Dae
    • Journal of the Korean Applied Science and Technology
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    • v.18 no.3
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    • pp.161-166
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    • 2001
  • While the equilibrium behaviour of surfactant solution is well studied, the understanding of the kinetics and pathways of structural transition under nonequilibrium conditions is only begining to develop. Attention has recently been directed mainly towards micellar kinectics, transitions between micellar and lamellar phases, vesicle fusion, and phases separation in microemulsions. This progress has profited greatly from developments that have taken place in various techniques and instruments.

Lipase-catalyzed esterification processing in natural polymer containing microemulsion-based organogel systems

  • Nagayama, Kazuhito;Imai, Masanao
    • Proceedings of the Membrane Society of Korea Conference
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    • 2004.05a
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    • pp.187-190
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    • 2004
  • Microemulsions gelled by the aid of natural polymers, i.e. microemulsion-based organogels (MBGs), have become of interest as novel tools for enzyme immobilization in hydrophobic solvents [1,2]. Sodium bis(2-ethylhexyl) sulfosuccinate (AOT)is frequently employed as an amphiphile for stable MBG formation.(omitted)

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Study of rganized Assemblies and Surfaces Using Picosecond Lasers

  • Bhattacharyya, Kankan
    • Journal of Photoscience
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    • v.6 no.3
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    • pp.123-128
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    • 1999
  • Dynamics of many ultrafast processes are markedly slowed down in various organized molecular assemblies compared to ordinary liquids. We will show that the solvation dynamics of water molecules is affected amost dramatically and is retarded by 3 ∼4 orders of magnitude in microemulsions, micells and lipids. We will also discuss how the access to fewer water molucules and the drastically altered local pH in an organized asembly affected the excited state proton transfer processes. Finally, we will show how surface second haromonic generation can be used to study the air-water surface.

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Enzymatic Synthesis of Lauric Acid Butyl Ester in Organic Media Containing Nonionic Surfactants (비이온 계면활성제를 포함한 유기 용액에서의 효소에 의한 라우르산부틸에스테르의 합성)

  • Cheong, Yong-Il;Lim, Kyung-Hee
    • Applied Chemistry for Engineering
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    • v.16 no.5
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    • pp.705-711
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    • 2005
  • The reaction of lauric acid vinyl ester with n-butanol was established to give lauric acid butyl ester by subtilisin A-catalyzed transesterification in organic media containing nonionic surfactants. Pyridine has been used as an organic solvent since it provides higher yields than other organic solvents. However, because of stench of pyridine, compounds enzymatically synthesized in pyridine may be unsuitable as ingredients for foods and drugs. Hence, in order to select an organic solvent to replace pyridine, sugar esters were synthesized with the protease in various organic media. However, no solvent paralleled pyridine in yields. On the basis of this result, pyridine-based W/O microemulsions containing nonionic surfactants and water were used in enzymatic synthesis of the sugar ester, and when Tween 60, Brij 56, or 1-O-octyl-${\beta}$-D-glucopyranose was used for the W/O microemulsions, the yield was higher.

Silica-encapsulated ZnSe Quantum Dots as a Temperature Sensor Media (온도센서용 실리카에 담지된 ZnSe 양자점 소재)

  • Lee, Ae Ri;Park, Sang Joon
    • Applied Chemistry for Engineering
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    • v.26 no.3
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    • pp.362-365
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    • 2015
  • Silica encapsulated ZnSe quantum dots (QDs) were prepared by employing two microemulsion systems: AOT/water/cyclohexane microemulsions containing ZnSe quantum dots with NP5/water/cyclohexane microemulsions containing tetraethylorthosilicate (TEOS). Using this method, cubic zinc blende nanoparticles (3 nm in diameter) were synthesized and encapsulated by silica nanoparticles (20 nm in diameter). The temperature dependence of photoluminescence (PL) for silica-encapsulated ZnSe QDs was investigated to evaluate this material as a temperature sensor media. The fluorescence emission intensity of silica-encapsulated ZnSe nanoparticles (NPs) was decreased with an increase of ambient temperature over the range from $30^{\circ}C$ to $60^{\circ}C$ and a linear relationship between the temperature and the emission intensity was observed. In addition, the temperature dependence of PL intensity for silica-encapsulated ZnSe NPs showed a reversible pattern on ambient temperature. A reversible temperature dependence of the luminescence combined with its insensitivity toward quenching by oxygen due to silica coating established this material as an attractive media for temperature sensor applications.

Formulation Design and Evaluation of Ursolic Acid Microemulsion Delivery System for Topical Formulation (마이크로에멀젼을 이용한 우르솔릭산 피부 적용제제의 설계 및 평가)

  • Park, Jong-Hee;Kyong, Kee-Yeol;Lee, Gye-Won;Jee, Ung-Kil
    • Journal of Pharmaceutical Investigation
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    • v.35 no.4
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    • pp.233-241
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    • 2005
  • Ursolic acid (UA), a bioactive triterpene acid, has been known to increase collagen content in human skin in addition to other actions such as anti-inflammatory, skin-tumor prevention and anti-invasion. However, it is poorly soluble in water. Therefore, we firstly prepared microemulsion system with benzyl alcohol, ethanol and Cremophor EL, RH 40 and Brij 35 as surfactant in order to increase solubility of UA and then prepared microemulsion was dispersed in o/w cream base for the topical delivery of UA in an effort to improve anti-wrinkle effect. The pseudo-ternary phase diagrams were developed and various microemulsion formulations were prepared using benzyl alcohol as an oil, Cremophor EL, RH 40 and Brij 35 as a surfactant. The droplet size of microemulsions was characterized by dynamic light scattering. The accumulation of VA in the skin from topical cream was evaluated in vitro using hairless mouse skins. The mean droplet size was $26.8{\pm}6.6$ nm for microemulsions II with Cremophor EL. All UA creams showed pseudoplastic flow and hysterisis loop in their rheogram, depending on the type of materials added in topical creams. The in vitro accumulation data demonstrated the UA topical cream prepared with the combination of Poloxamer 407 and Xanthan gum as a copolymer showed higher accumulation percentage than those prepared with either Poloxamer 407 or Xanthan gum. These results suggest that UA topical cream using microemulsion systems may be promising for the topical delivery of UA.

Solubilization of Talniflumate in Microemulsion Systems (마이크로에멀젼을 이용한 탈니플루메이트의 가용화)

  • Lee, Gye-Won;Cho, Young-Ho;Kim, Hak-Hyung;Kim, Sock-Young;Kim, Do-Kyun;Kim, Eun-Hea
    • Journal of Pharmaceutical Investigation
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    • v.38 no.3
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    • pp.171-176
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    • 2008
  • Talniflumate is a nonsteroidal anti-inflammatory drug (NSAID), which has been used treat of rheumatoid diseases, is insoluble in water, therefore it has low bioavailability after oral administration. The purposes of this study were to prepare O/W or W/O microemulsions for solubilization of poorly water soluble drug, talniflumate and to formulate into other dosage form. For this purpose, we made O/W or W/O microemulsion with oil(soybean oil, IPM), surfactant (Cremophor $EL^{(R)}$, Tween 80) and water or propylene glycol and evaluated solubility of talniflumate. The microemulsion systems were very stable and showed transmittance above 95% without flocculation or aggregation. Especially, the solubility of talniflumate in the formulation B-1 containing 18% of isopropyl myristate and 71% of tween 80 was 10 times higher than that of other O/W microemulsions. The addition of propylene glycol and N-methylglutamine to the fomulation B-1 showed excellent capacity on the solubilization of talniflumate and the percentage was almost 2.0%. These results suggest that the microemulsion system may be promising for the solubility improvement of talniflumate.

Effect of Continuous Oil Phase on Preparation of Silver Halide Nanoparticles using AOT-Based W/O Microemulsions (AOT W/O 마이크로에멀젼을 이용한 할로겐화은 나노입자 제조에서 연속상 오일의 영향)

  • Jung, KilYong;Lim, JongChoo
    • Korean Chemical Engineering Research
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    • v.45 no.4
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    • pp.364-371
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    • 2007
  • Effects of continuous oil phase on silver halide nanoparticles were investigated where nanoparticles were prepared using two different types of water-in-oil(W/O) microemulsions containing silver and halide, respectively. Phase behavior experiments for ternary systems containing AOT surfactant, hydrocarbon oil and aqueous solution of an inorganic salt showed that the region of one phase W/O microemulsion was found to be broadened with an increase in the alkyl chain length of a hydrocarbon mainly due to an increase in hydrophilic nature of a surfactant. With the information of phase behavior experiments, silver halide nanoparticles were prepared using different AOT-based microemulsion systems and photomicrographs obtained by transmission electron microscopy indicated that about 10 nm size particles of relatively spherical shape were obtained. It has been found that an increase in alkyl chain length of a hydrocarbon results in a decrease in particle size because of higher intermicellar exchange rate among microemulsion drops. The average particle size was also found to increase with the inorganic salt composition of initial aqueous solution.

Encapsulation of ZnSe Quantum Dots within Silica by Water-in-oil Microemulsions (마이크로에멀전을 이용한 실리카에 담지된 ZnSe 양자점 제조)

  • Lee, Areum;Kim, Ji Hyeon;Yoo, In Sang;Park, Sang Joon
    • Applied Chemistry for Engineering
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    • v.22 no.3
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    • pp.328-331
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    • 2011
  • ZnSe quantum dots (QDs) were prepared by employing water-containing Dioctyl sodium sulfosuccinate (AOT) reversed micelles (microemulsions) and the silica-encapsulated ZnSe QDs were obtained by a direct injection of tetraethyl orthosilicate (TEOS) into the microemulsion system. When the QDs were coated by silica, well-defined spherical shapes were formed and the average size of the QDs was near 7 nm. In addition, the photoluminescence (PL) efficiency of the QDs was reduced from 8.0 to 1.1% as they were encapsulated by silica. However, the solid layers of the silica-encapsulated ZnSe QDs on gold surfaces showed the excellent photostability. In particular, they are cadmium free and thus, less toxic. Moreover, the present method does not require a hot reaction temperature or extremely toxic H2Se gas as a Se precursor. Accordingly, the method can be a safer and more economical process for producing silica-encapsulated ZnSe QDs, which may be a potential media for biosensors.

Synthesis of Long Chain Alkyl Urocanate and Solubilization in Organic Solvent (긴사슬 알킬 우로칸에스테르의 합성 및 유기물질에서의 가용성)

  • Ro, Y.C.;Jeong, H.K.;Nam, K.D.;Lee, J.H.
    • Journal of the Korean Applied Science and Technology
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    • v.10 no.1
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    • pp.83-91
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    • 1993
  • The syntheses of urocanic acid esters was optimized, starting from p-toluenesulfonic acid salt of this acid and long chain fatty alcohols in the organic solvent and extracting water from it by means of azeotropic Compound. The salts of these urocanic acid esters showed amphoteric properties, but their micellization enhances their rate of hydrolysis leading to the free amine. Nevertheless the long chain gives to the esters themselves an amphoteric character allowing their solubilization in micellar media and in microemulsions the result, yield could enhanced.