• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.295-295
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• 2006

In present study, poly(acrylic acid) (PAA) and hydrophobically modified poly(ethylene oxide) (HM-PEO) multilayers based on the hydrogen bonding between the component polymer pair have been prepared by the LbL deposition method. Dip assembled HM-PEO/PAA multilayers yield unique film morphologies in comparison with PEO/PAA multilayers due to the micellar formation of HM-PEO owing to the hydrophobic attraction between alkyl chains end-capped with the PEO chains. Individual HM-PEO micelles were connected through the bridging PEO chains to form temporary networks on multilayer surface and induced peculiar surface morphology on HM-PEO/PAA multilayers above the critical number of bilayers.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.85-85
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• 2006

The micellization behavior and the metal-nanoparticle formation in PDEAEMA-b-PHEGMA double hydrophilic block copolymers are investigated. The hydrophobic PDEAEMA block is pH-sensitive: at low pH it can be protonated and it becomes hydrophilic, leading to molecular solubility, whereas at higher pH micelles are formed; the behavior is studied by DLS, NMR and AFM. In these micellar nanoreactors, metal nanorystals nucleate and grow upon reduction with sizes in the range of a few nm's as observed by TEM and XRD. Similarly, metal nanocrystals can be formed within pH-sensitive microgels (${\sim}250nm$ in diameter), synthesized by emulsion copolymerization of DEAEMA, which also exhibit reversible swelling properties in water by adjusting the pH.

• 한국식품과학회지
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• 제35권5호
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• pp.835-840
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• 2003

Hexane/aerosol OT(AOT)/물로 구성된 역미셀의 water pool내에서 알긴산나트륨과 염화칼슘의 반응성을 이용하여 알긴산 조미세입자의 제조를 시도하였다. 주사전자현미경(SEM) 관측결과 미세한 입자들이 형성됨을 확인하였으며 이는 알긴산나트륨 함유 water pool과 염화칼슘 함유 water pool이 상호 접촉에 의해 내부물질의 교환이 가능함을 의미한다. 역미셀의 water pool 크기에 영향을 주는 유화제(AOT)에 대한 물의 몰농도 비율인 Wo 값을 5에서 10으로 증가함에 따라 미세입자의 크기가 유의적으로 증가하였으며 제조된 미세입자간의 입도특성을 비교한 결과, 각 입자의 표면적, 최장식경(max diameter), 최단직경(min diameter), 평균직경(mean diameter). 그리고 각 입자의 둘레 길이는 Wo 값이 증가함에 따라 유의적으로 증가하였다(p<0.05). Wo 값이 15 이상에서는 입자간 응집이 발생하였으며 Wo 값이 20인 경우에는 안정한 역미셀의 형성이 불가능하였다. 제조된 입자의 평균직경은 Wo=5에서 $2.08\;{\mu}m$이었으며 10인 경우 $2.66\;{\mu}m$으로 나타났으며 이는 기존에 보고 된 알긴산 입자의 크기에 비하여 약 $70{\sim}1000$배 가량 작은 수준이었다. 한편, 입자의 구형도는 분석된 Wo 구간에서 유의적인 자이를 보이지 않음으로써 역미셀에 의해 형성되는 입자의 외부형태는 안정한 역미셀을 형성하는 Wo 구간에서는 크게 변화하지 않는 것으로 판단된다.

• Macromolecular Research
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• 제12권1호
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• pp.127-133
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• 2004

We have studied the surface micelle formation of polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) at the air-water interface. A series of four PS-b-P2VPs were synthesized by anionic polymerization, keeping the PS block length constant (28 kg/㏖) and varying the P2VP block length (1, 11, 28, or 59 kg/㏖). The surface pressure-area ($\pi$-A) isotherms were measured and the surface morphology was studied by atomic force microscopy (AFM) after Langmuir-Blodgett film deposition onto silicon wafers. At low surface pressure, the hydrophobic PS blocks aggregate to form pancake-like micelle cores and the hydrophilic P2VP block chains spread on the water surface to form a corona-like monolayer. The surface area occupied by a block copolymer is proportional to the molecular weight of the P2VP block and identical to the surface area occupied by a homo-P2VP. It indicates that the entire surface is covered by the P2VP monolayer and the PS micelle cores lie on the P2VP monolayer. As the surface pressure is increased, the $\pi$-A isotherm shows a transition region where the surface pressure does not change much with the film compression. In this transition region, which displays high compressibility, the P2VP blocks restructure from the monolayer and spread at the air-water interface. After the transition, the Langmuir film becomes much less compressible. In this high-surface-pressure regime, the PS cores cover practically the entire surface area, as observed by AFM and the limiting area of the film. All the diblock copolymers formed circular micelles, except for the block copolymer having a very short P2VP block (1 kg/㏖), which formed large, non-uniform PS aggregates. By mixing with the block copolymer having a longer P2VP block (11 kg/㏖), we observed rod-shaped micelles, which indicates that the morphology of the surfaces micelles can be controlled by adjusting the average composition of block copolymers.

• Journal of Microbiology and Biotechnology
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• 제20권7호
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• pp.1061-1068
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• 2010

The biological synthesis of nanoparticles has gained considerable attention in view of their excellent biocompatibility and low toxicity. We isolated and purified rhamnolipids from Pseudomonas aeruginosa strain BS-161R, and these purified rhamnolipids were used to synthesize silver nanoparticles. The purified rhamnolipids were further characterized and the structure was elucidated based on one- and two-dimensional $^1H$ and $^{13}C$ NMR, FT-IR, and HR-MS spectral data. Purified rhamnolipids in a pseudoternary system of n-heptane and water system along with n-butanol as a cosurfactant were added to the aqueous solutions of silver nitrate and sodium borohydride to form reverse micelles. When these micelles were mixed, they resulted in the rapid formation of silver nanoparticles. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). The nanoparticles formed had a sharp adsorption peak at 410 nm, which is characteristic of surface plasmon resonance of the silver nanoparticles. The nanoparticles were monodispersed, with an average particle size of 15.1 nm (${\sigma}={\pm}5.82$ nm), and spherical in shape. The EDS analysis revealed the presence of elemental silver signal in the synthesized nanoparticles. The formed silver nanoparticles exhibited good antibiotic activity against both Grampositive and Gram-negative pathogens and Candida albicans, suggesting their broad-spectrum antimicrobial activity.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.667-674
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• 2007

Phase behavior for the mixed aqueous surfactant systems of cationic octadecyl trimethyl ammonium chloride (OTAC)/anionic ammonium dodecyl sulfate (ADS)/water was examined. Below the total surfactant concentrations of 1.5 m molal, mixed micelles were formed. At the total surfactant concentrations higher than 1.5 m molal, there appeared a region where mixed micelles and vesicles coexist. As the surfactant concentration increased, the systems looked very turbid and much more vesicles were observed. The vesicles were spontaneously formed in this system and their existence was observed by negative-staining transmission electron microscopy (TEM), small-angle neutron scattering (SANS) and encapsulation efficiency of dye. The vesicle region was where the molar fraction α of ADS to the total mixed surfactant was from 0.1 to 0.7 and the total surfactant concentration was above 5 × 10-4 molality. The size and structure of the vesicles were determined from the TEM microphotographs and the SANS data. Their diameter ranged from 450 nm to 120μm and decreased with increasing total surfactant concentration. The lamellar thickness also decreased from 15 nm to 5 nm with increasing surfactant concentration and this may be responsible for the decrease in vesicle size with the surfactant concentration. The stability of vesicles was examined by UV spectroscopy and zeta potentiometry. The vesicles displayed long-term stability, as UV absorbance spectra remained unchanged over two months. The zeta potentials of the vesicles were large in magnitude (40-70 mV) and the observed longterm stability of the vesicles may be attributed to such high ζ potentials.

• 한국재료학회지
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• 제22권4호
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• pp.207-210
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• 2012

The preparation of $Sm_2O_3$ doped $CeO_2$ in Igepal CO-520/cyclohexane reverse micelle solutions has been studied. In the present work, we synthesized nanosized $Sm_2O_3$ doped $CeO_2$ powders by reverse micelle process using aqueous ammonia as the precipitant; hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase, and poly (xoyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by Thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), and Transmission electron microscopy (TEM). The crystallite size was found to increase with increase in water to surfactant (R) molar ratio. Average particle size and distribution of the synthesized $Sm_2O_3$ doped $CeO_2$ were below 10 nm and narrow, respectively. TG-DTA analysis shows that phase of $Sm_2O_3$ doped $CeO_2$ nanoparticles changed from monoclinic to tetragonal at approximately $560^{\circ}C$. The phase of the synthesized $Sm_2O_3$ doped $CeO_2$ with heating to $600^{\circ}C$ for 30 min was tetragonal $CeO_2$. This study revealed that the particle formation process in reverse micelles is based on a two step model. The rapid first step is the complete reduction of the metal to the zero valence state. The second step is growth, via reagent exchanges between micelles through the inter-micellar exchange.

• Preventive Nutrition and Food Science
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• 제9권1호
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• pp.98-106
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• 2004

Tomatoes and tomato products are the major source of lycopene in the diet. The bioavailability of lycopene is different in raw tomatoes compared to processed tomato products. This is due to the chemical and physical properties of the different lycopene isomers. All-trans-lycopene is found in raw tomatoes and is a poor bioavailable source, whereas, processed tomato products are more bioavailable because they contain more cis-isomers. Heat and mechanical processing of tomatoes induces rupture of the cell walls, thereby releasing lycopene from its food matrix. Heat processing also induces cis-trans isomerization and disrupts protein-carotenoid complexes. Many dietary components also impact lycopene bioavailability, like the amount and type of fat present with the intake and processing of tomato products, the amount and type of fiber present, and the interaction between carotenoids. Fundamentally, anything that enhances formation and incorporation of lycopene in bile acid micelles increases bioavailability, and the opposite is true in that anything that interferes with micelle formation decreases bioavailability.

• Archives of Pharmacal Research
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• 제26권8호
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• pp.653-658
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• 2003

It has been reported that at low temperature region, poloxamers existed as a monomer. Upon warming, an equilibrium between unimers and micelles was established, and finally micelle aggregates were formed at higher temperature. In this study, the fluorescence spectroscopy was used to study the micelle formation of the poloxamer 407 in aqueous solution. The excitation and emission spectra of pyrene, a fluorescence probe, were measured as a function of the concentration of poloxamer 407 and temperature. A blue shift in the emission spectrum and a red shift in the excitation spectrum were observed as pyrene transferred from an aqueous to a hydrophobic micellar environment. From the $I_1/I_3 and I_{339}/I_{333}$ results, critical micelle concentration (cmc) and critical micelle temperature (cmt) were determined. Also, from the fluorescence spectra of the probe molecules such as 8-anilino-1-naphthalene sulfonic acid and 1-pyrenecarboxaldehyde, the blue shift of the $\lambda_{max}$ was observed. These results suggest a decrease in the polarity of the microenvironment around probe because of micelle formation. The poloxamer 407 above cmc strongly complexed with hydrophobic fluorescent probes and the binding constant of complex increased with increasing the hydrophobicity of the probe.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.107-114
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• 2005

Molecular aggregates of surfactant molecules consisting of one or more bilayers arranged in a hollow, closed, usually spherical geometry are termed “esicles”or “iposomes” In recent years it has been found that in certain systems the vesicular structure forms spontaneously and is long lived, and it has been suggested that these structures may in fact constitute the equilibrium state in these cases (as is true of micelles) This paper deals with the mixed CMC, vesicles, phase behavior, phase transition, geometrical structure, their formation and characterization in the aqueous solutions of mixed cationic/anionic surfactants systems. TEM micrographs revealed that the vesicles were of spherical shape and that their size was of around 180 nm. The zeta potentials are positive at CGS1-rich regions and negative at SLES-rich regions. In the region where SLES/CGS1 (6/4), the zeta potentials are very small, implying that the vesicles at this surfactant ratio may be less stable. At other surfactant ratios, the vesicles are thought to be stable, supported by large absolute values of zeta potentials and little change in UV absorbance for several months.