• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.42.2-42.2
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• 2011

$TiO_2$ films were modified by adding a glass frit as a light scattering particle and applied to an anode electrode in dye-sensitized solar cells (DSSCs) to enhance the adhesion between $TiO_2$ and fluorine doped transparent oxide (FTO). Low melting point glass frits at contents of (3 to 7wt%) were added to the nano crystalline $TiO_2$ films. The light scattering properties, photovoltaic properties and microstructures of the photo electrodes were examined to determine the role of the low glass transition temperature ($T_g$) glass frit. Electrochemical impedance spectroscopy, Brunauer-Emmett-Teller method and scratch test were conducted to support the results. The DSSC with the $TiO_2$ film containing 3wt% low Tg glass frit showed optimal performance (5.1%, energy conversion efficiency) compared to the $TiO_2$-based one. The photocurrent density slightly decreased by adding 3wt% of the frit due to its large size and non conductivity. However, the decrease of current density followed by the decrease of electron transfer due to the large frit in $TiO_2$ electrode was compensated by the scattering effect, high surface area and reduced the electron transfer impedance at the electrolyte-dye-$TiO_2$ interface. The stability of the photo electrodes was improved by the frit, which chemically promoted the sintering of $TiO_2$ at relatively low temperature ($450^{\circ}C$).

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.86-88
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• 2006

The novel linear- (V-LUM) and cross-type macromonomers (C-VUM) of vinyl-terminated bifunctional polyurethane were synthesized and applied to the dispersion polymerization of styrene and MMA in ethanol. The existence of the vinyl terminal groups and the grafted macromonomer with styrene and PMMA was verified using 1H NMR and 13C NMR. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The macromonomer can efficiently stabilize higher surface area of the particles compared to a conventional stabilizer, PVP. The grafting ratio of the PS calculated from 1H NMR linearly increased up to 0.048 with 20 wt % of the macromonomer and the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal stability were obtained. Furthermore, the stable and monodisperse PMMA microspheres having a weight-average diameter of $5.09{\mu}m$ and a good uniformity of 1.01 were obtained with 20 wt% L-VUM. The molecular weight increased, but the size of the PMMA particles decreased with the macromonomer concentration due to the increased stabilizing effect. The molecular weight of the PMMA was approximately two fold higher than that by a conventional PVP. The L-VUM acts as a reactive stabilizer, which gives polyurethane-grafted PS or PMMA with a high molecular weight. In addition, the XPS result showed that the C-PS (PS using the C-VUM) was anchored with a larger amount of PEG than that of the L-PS (PS using the L-VUM) on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed.

• Polymer(Korea)
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• v.33 no.5
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• pp.477-484
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• 2009

Suspension polymerization with hydrophobic silica as a stabilizer and AIBN as an initiator was conducted to synthesize PBMA particles and PBMA composite particles containing carbon black. Surface modification of silica particles by controlling pH revealed that 90% of them functioned as stabilizer and 10% were incorporated into PBMA particles. While stabilizer concentration had no impact on reaction kinetics and particle diameter, an increase in stabilizer concentration displayed an increase in molecular weights when it exceeded 1.67 wt%. An increase in initiator concentration and reaction temperature decreased molecular weights in close agreement with the theoretical equation. An increase in carbon black concentration from 1 to 7 wt%, relative to the monomer, showed a progressive decrease in reaction conversion. As carbon black was increased from 3 to 5 wt%, glass transition showed a $4^{\circ}C$ increase. The presence of carbon black was confirmed by TEM while its concentration was measured by TGA.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.203-207
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• 2009

In the NCAs(non-conductive adhesive) for adhesion of Micro Electro Mechanical System(MEMS), there are some problems such as delamination and cracking, because of the differences of CTE(coefficients of thermal expansion) between NCAs and substrates. Addition of inorganic particle or flexibilizer have been performed to solve those problems. In this study, to improve the flexibility of epoxy adhesive, epoxy/siloxane composites were prepared by adding 1, 3, or 5 phr of amino modified siloxane(AMS). Glass transition temperatures(Tg), moduli and CTE of those composites were measured to confirm effects of siloxane on thermal/mechanical properties of siloxane/epoxy-composites. Tg of AMS/epoxy-composites decreased from $134^{\circ}C$ to $122^{\circ}C$ with increasing AMS contents and moduli decreased from 2,425 MPa to 2,143 MPa with increasing AMS contents. But CTE of AMS/epoxy-composites increased from $67ppm/^{\circ}C$ to $71ppm/^{\circ}C$ with increasing AMS contents. In short, the addition of siloxane is effective for enhancing the flexibility of epoxy but leads to the decrease of Tg.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.145-152
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• 1996

A fine oil-in-water (O/W) emulsion using nonaqueous emulsification technique was developed and the behaviors of POE(25)octyldodecyl ether in nonaqueous solvent/oil systems were studied by observing the surface tension, interfacial tension, turbidity and transition temperature. It was found that POE(25)octyldodecyl ether existed soluble in nonaqueous solvent while, in aqueous system, it formed micelles. So, when a solvent, like glycerine in which POE(25)octyldodecyl ether has poor solubility, was added, POE(25)octyldodecyl ether moved to the surface. After saturated at surface, POE(25) octyldodecyl ether began to precitate. The mean particle size of the final emulsion was 230nm. Also, the emulsion system was stable at 0, 25, 40, $50^{\circ}C$ and cycling test for a month, while the conventional emulsion system showed unstability. It is concluded that, by pertinent combination of solvents, the adsorption efficiency of surfactant could be improved.

• Elastomers and Composites
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• v.43 no.3
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• pp.157-165
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• 2008

Suspension polymerization was carried out to synthesize poly(butyl methacrylate) (PBMA) composite particles containing carbon black. Water was selected as a reaction medium, hydrophobic silica as a stabilizer and azobisisobutyronitrile as an initiator. Concentration of stabilizer was varied from 0.67 to 2.55 weight% with respect to the water, and that of initiator was varied from 0.25 to 3.00 weight% with respect to the butyl methacrylate (BMA) monomer. All polymerization reactions were conducted at 75$^{\circ}C$. It is found that stabilizer concentration has no impact on reaction kinetics, while an increase in initiator concentration enhances polymerization reaction rate. Increase of carbon black concentration from 1 to 3 to 5 wt% into PBMA displayed progressive decrease in reaction conversion. The particle diameter of PBMA composite particles containing carbon black was found to be between 5 and 30 ${\mu}m$. Glass transition was determined to range from 23.8 to 24.7$^{\circ}C$, irrespective of variation in the concentration of stabilizer, initiator or carbon black.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.177-185
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• 2017

In the present work, the interaction of fatty acid with vesicle membrane of phospholipids was investigated using 3 different kinds of fatty acids such as stearic acid (SA), oleic acid (OA) and linoleic acid (LA). Basically, the same trend has been found in 3 fatty acid systems. The addition of fatty acid produced a close packing of liposome due to the penetration of fatty acid molecules into liposome vesicles, which resulted in a decrease in size and an increase in zeta potential of liposome. However, excessive addition of fatty acid produced a transition from liposomes to aggregates of lipid particles having polymorphic structure. The membrane fluidity, characterized by measuring membrane deformability and fluorescence anisotropy ratio of liposomes, was in good agreement with measurement results of transmission electron microscopy (TEM) and particle size. The minimum size and closest packing of liposome with SA, OA and LA were found when the molar ratios of fatty acid to lecithin were 0.70, 0.50, and 0.25 respectively.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.11a
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• pp.91-97
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• 2000

The conventional model did not take momentum conservation into consideration when the electron absorbs and emits the photons. II-ray provides momentum conservations on any directions of the entering photons, and also the electrons have radial momentum conservations and fully elastic bouncing between two atoms, in the new atom model. Conventional atom model must be criticized on the following four points. (1) Natural motions between positive and negative entities are not circular motions but linear going and returning ones, for examples sexual motion, tidal motion, day and night etc. Because the radius of hydrogen atom's electron orbit is the order of 10$^{-11}$ m and the radia of the nucleons in the nucleus are the order of 10$^{-l4}$m and then the converging n-gamma rays to the nucleus have so great circular momentum, the electron can not have a circular motion. We can say without doubt that any elementary mass particle can have only linear motion because of the n-rays' hindrances, near the nucleus. (2) Potential energy generation was neglected when electron changes its orbit from outer one to inner one. The h v is the kinetic energy of the photo-electron. The total energy difference between orbits comprises kinetic and potential energies. (3) The structure of the space must be taken into consideration because the properties of the electron do not change during the transition from outer orbit to inner one even though it produces photon. (4) Total energy conservation law applies to the energy flow between mind and matter because we daily experiences a interconnection between mind and body. An understanding of the mechanisms responsible for the control of normal proliferation and differentiation of the various cell types which make up the human body will undoubtedly allow a greater insight into the abnormal growth of cells, A large body of biochemical evidence was eventually used to generate a receptor model with an external ligand binding domain linked through a single trans-membrane domain to the cytoplasmic tyrosine kinase and autophosphory-lation domains. The ligand induced conformational change in the external domain generates either a push-pull or rotational signal which is transduced from the outside to the inside of cell.l.ell.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.632-637
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• 2009

Poly(${\varepsilon}-caprolacton$)/ethyl cellulose (PCL/EC) microcapsules containing pluronic F127 were prepared by a spray drying method. The aqueous phase, 20% of pluronic F127 was dissolved in distilled water, and the organic phase, 5% of PCL and EC were dissolved in dichloromethane. The microcapsules were obtained by spray drying the water-in-oil (W/O) emulsion. According to the data of scanning electron microscopy and particle analyzer, tens of micro size microcapsules were observed. On a differential scanning calorimeter, the phase transition temperatures of microcapsules were observed and they were found around those of pluronic F127 and poly(${\varepsilon}-caprolacton$), which were the main components of the microcapsules. At the range of $30{\sim}45^{\circ}C$, temperature-dependent release properties were investigated using fluorescein isothicyanate-dextran (FITC-dextran) and blue dextran as a model drug. When the temperature was increased, the degree of release of microcapsule was also increased. FITC-dextran, the relative low molecular weight, was more released than blue-dextran.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.794-801
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• 1996

$TiO_2$ fine powders were synthesized via hydrolysis reaction of titanium isopropoxide in isopropanol solvent and the reaction rates were studied by use of UV spectroscopic method. The reactions were controlled to proceed to pseudo-first-order reaction in the presence of excess water in isopropanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reactions using $D_2O$ were also carried out to determine the catalytic character of water. n value of water molecules in transition state and the thermodynamic parameters showed that the reaction proceeded by $S_N2$ mechanism. $TiO_2$ powders synthesized in this reaction were almost spheric forms and had average particle size of $0.3{\mu}m$ diameter.