• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.224-231
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• 1990

To improve the dispersion of platinum catalyst, the effects of carbon black surface treatment, solvents, surfactants, and ultrasonic homogenizing were examined. Upon introducing the hydrophilic groups acting as an anchorage center of the catalyst on the surface of carbon black by oxidation, the migrating and growing of platinum particles(or ions) during reduction could be restricted. When mixed solvents, surfactants, or ultrasonic homogenizer were used to disperse catalysts on the carbon black, the dispersion of catalyst could be improved, due to the good permeation of chloroplatinic acid through the pore of carbon black. Among the impregnation methods, the method using ultrasonic homogenizer with mixed solvent was the most excellent. Using this method the particle sized could be minimized in less than $30A^{\circ}$ and distributed homogeneously.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.296-304
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• 1992

Porous polyurethane membrane was prepared by the phase inversion process with variable permeability in response to pH and solvent composition. Hydrophilic polymers were grafted on the surface of the symmetric porous membrane. Porous polyurethane membrane was obtained in DMSO/methanol. It was subsequently grafted with acrylamide on the surface with ceric ammonium nitrate(CAN) as a initiator, followed by the hydrolysis to obtain poly(acrylic acid-g-urethane) (PAA-g-PU) membrane. The change in permeability of vitamine $B_2$(riboflavin) was investigated through PAA-g-PU. For PAA-g-PU membrane, permeability increased with the decrease in pH, and with an increase in solvent content in sink solution.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.78-81
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• 2010

Surface modification of silica nanoparticles was investigated using an aerosol self assembly. Stearic acid was used as surface treating agent. A two-fluid jet nozzle was employed to generate an aerosol of the colloidal suspension, which contained 20 nm of silica nanoparticles, surface modifier, and ethyl alcohol. Powder properties such as morphology, specific surface area and pore size distribution were analyzed by SEM, BET and BJH methods, respectively. Surface properties of the silica power were analyzed by FT-IR. The OH bond of the $SiO_2$ surface was converted to a C-H bond. It was revealed that the hydrophilic surface changed to a hydrophobic one due to the aerosol self assembly. Morphology of the surface treated powder was nanostructured with lots of pores having an average diameter of around $2\;{\mu}m$. Depending on the stearic acid concentration (0.25 to 1.0 wt%), the pore size distribution of the particles and the degree of hydrophobicity ranged from 1.5 nm to 180 nm and 29.6% to 50.2%, respectively.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.2
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• pp.165-174
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• 2017

This study reports a synthesis of an amphiphilic linear block copolymer consisting of a hydrophobic poly (lactide) (PLA) block and a hydrophilic hyperbranched polyglycerol (hbPG) block, PLA-b-hbPG. Simple chemical modification of the hbPG block with 4-hydroxycinnamic acid (CA) led to a photo-crosslinkable block copolymer, PLA-b-hbPG-CA. Nanosized micelles of the block copolyemrs were used as drug carriers for sustainable release. The hbPG shell made of a small molecular weight hbPG block showed excellent hydrophilicity, which can minimize in vivo toxicity. The UV-crosslinked PLA-b-hbPG-CA micelles loaded with drugs colud be served as a drug delivery carrier for its biocompatibility and self-assembled structures.

• Membrane Journal
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• v.28 no.5
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• pp.361-367
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• 2018

In this study, the nanofiltration (NF) composite membranes for the low pressure use were prepared using polyvinylidene fluoride (PVDF) hollow fiber membrane as a supporter. Poly styrene sulfonic acid (PSSA) and polyethyleneimine (PEI) were coated onto the PVDF membrane by both layer-by-layer and salting-out methods. To characterize the prepared NF membranes in terms of the flux and salt rejection, 100 mg/L feed solutions of NaCl, $MgCl_2$, and $CaSO_4$ were used at the flow rate of 1 L/min and the operating pressure of 2 bar at room temperature. The NF membranes coated with 20,000 ppm PSSA (ionic strength 1.0) solution for 3 minutes and then 30,000 ppm (ionic strength 0.1) solution for 1 minute were observed the best performance. The permeability and salt rejection were 38.5 LMH, 57.1% for NaCl, 37.9 LMH and 90.2% for $MgCl_2$ and 32.4 LMH and 54.6% for $CaSO_4$, respectively.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.541-547
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• 2015

Formation of disinfection by-products (DBPs) including trihalomethans (THMs) and haloacetic acids (HAAs) from chlorination of six different species (Chlorella vulgaris, Scenedesmus sp., Anabaena cylindrical, Microcystis aeruginosa, Asterionella formosa and Aulacoseira sp.) of algal extracellular organic matter (EOM). The EOM characteristics evaluation of six algal species reaching at the stationary phase in the growth curve showed most of its SUVA254 showed below 1 and this means hydrophilic organic matter is much higher than hydrophobic organic matter. Chloroform formation potential (CFFP), dichloroacetic acid formation potential (DCAAFP) and trichloroacetic acid formation potential (TCAAFP) were mainly composed of THMFP and HAAFP in the EOM of various algal species. In the case of THMFP/DOC and HAAFP/DOC values, EOM of blue-green algae has appeared highest and EOM of green algae and diatom in order. THMFP/DOC was higher than HAAFP/DOC in EOM of blue-green algae. In comparison of formation potential by unit DOC composed of HAAFP in algal species EOM, DCAAFP/DOC was 1.5 times to 7.5 time higher than TCAAFP/DOC in the EOM of blue-green algae, while DCAAFP/DOC was found to be relatively high compared to TCAAFP/DOC in the EOM of green algae and diatom.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.298-305
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• 2016

The development of non-precious metal based electrocatalysts is highly desired for the oxygen reduction reaction (ORR) as alternates to noble metal based ORR electrocatalysts. Herein, we report mononulcear copper(II) complex $[CuLbpy]ClO_4$ (L=4-[(2-hydroxyphenylimino)methyl]benzoic acid) containing poly(allylamine.HCl) polymer (PAlACuLbpy) as an electrocatalyst for oxygen reduction reaction (ORR). PAlACuLbpy was mixed with poly(acrylic acid) and tetraethylortho silicate to prepare a composite and then deposited on the screen printed electrode surface. The modified electrode (PAlACuLbpy/PCE) is highly stable and showed a quasi-reversible redox behavior with $E_{1/2}=-0.2V$ vs. Ag/AgCl(3 M KCl) in 0.1 M phosphate buffer at pH 7 under argon atmosphere. PAlACuLbpy/PCE exhibited a remarkable ORR activity with an onset potential of -0.1 V vs Ag/AgCl in 0.1 M PB (pH 7) in the presence of oxygen. The kinetics for ORR was studied by rotating disk voltammetry in neutral aqueous medium and the results indicated that the number of electrons involving in the ORR is four and the conversion products are water and hydrogen peroxide.

• Journal of Adhesion and Interface
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• v.2 no.3
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• pp.1-8
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• 2001

Epoxy composites filled with natural zeolite was prepared to investigate the effects of silane coupling agent, ${\gamma}$-APS (${\gamma}$-aminopropyltriethoxysilane)on the surface free energy, tensile properties and interfacial morphology. The value of Lifshitz-van der Waals component, ${\gamma}{\frac{LW}{SV}}$ for polar was $19.22mJ/m^2$ and increased, while that of Lewis acid-base component, ${\gamma}{\frac{AB}{SV}}$ for polar was $15.27mJ/m^2$ and decreased with the increasing content of ${\gamma}$-APS treatment. It is due that the surface of the zeolite is more coated by hydrophobic of alkyl group than hydrophilic amine or hydroxyl group. The tensile strength and Young's modulus of epoxy system were improved by the treatment with ${\gamma}$-APS due to the strong interface bonding, which was confirmed by SEM.

• Journal of Pharmaceutical Investigation
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• v.38 no.2
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• pp.119-126
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• 2008

Solid dispersions of poorly water-soluble drug, sibutramine, were prepared with hydrophilic polymer, poly-N-vinylpyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC) and organic acid, citric acid, to improve the solubility of drug. Physicochemical variation and shape of microsphere were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FT-IR). Microspheres containing additives showed more spherical shape than non additive microspheres. In vitro release behavior of microspheres presented at simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). The solid dispersion form transformed the drug into an amorphous state and dramatically improved its dissolution rate. These data suggest that the solid dispersion technique is an effective approach for developing the appetite depressant drug products and various pharmaceutical excipients are able to control the release behaviors.