• Journal of Adhesion and Interface
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• v.13 no.3
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• pp.101-108
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• 2012

Narrowly dispersed poly(BMA-co-MMA) and PBMA latices (PSD : 1.002~1.008) were synthesized successfully by surfactant-free emulsion polymerization with 2,2' azobis(2-methyl-propionamidine) dihydrochloride (AIBA) and $K_2S_2O_8$ (KPS). The number average particle diameter and the number average molecule weight were found to be 160~494 nm and (1.25~7.55) ${\times}10^4$, respectively. The influences of BMA/MMA ratio, monomer and initiator concentrations, addition of DVB/EGDMA crosslink agent, and polymerization temperature on the polymerization rates and on the particle size and molecular weight were studied. The rate of polymerization increased with increasing MMA concentration in BMA/MMA weight ratio. The particle diameter as well as the polymer molecular weight could be controlled easily by controlling the BMA/MMA weight ratio, monomer concentration, AIBA and KPS concentration, and polymerization temperature.

• Composites Research
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• v.30 no.1
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• pp.41-45
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• 2017

Magnetite nanoparticles were synthesized by adding an ammonium hydroxide to a mixed solution of iron (II) and (III) chlorides. A silicon surfactant of ${\alpha},{\omega}$-(3-aminopropyl)polydimethylsiloxane was adsorbed on the particles as dispersant and a polydimethylsiloxane polymer was used to prepare ferrofluids of silicone oil base. Fluorinated surfactants of anionic ammoniated perfluoroalkyl sulfonamide and nonionic fluoroaliphatic polymeric esters were applied to the particles and a perfluoropolyether was used to prepare ferrofluids of fluorine oil base. The experimental conditions were used for preparing the ferrofluids with concentrations of 200, 300 and 400 mg/mL, and density, magnetization and viscosity of the products were characterized. The density values increased in proportion to the concentration, indicating 1.11-1.27 g/mL for silicone-oil-based fluids and 1.95-2.10 g/mL for fluorine-oil-based fluids in the range of 200-400 mg/mL. The saturation magnetization of the silicone-oil-based and fluorine-oil-based fluids indicated 14.7, 24.4, and 30.7 mT and 15.8, 23.3, and 33.7 mT for 200, 300, and 400 mg/mL, respectively, depending on the content of magnetic particles in the fluid. The viscosity of the silicone-oil-based ferrofluids was highly stable compared to that of the fluorine-oil-based with increasing temperatures. The ferrofluids are usually applied to seals and speakers with the silicone base and to seals with the fluorine base.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.715-725
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• 1996

This study represents the synthetic characteristics of styrene-DVB copolymer which is used as a catalyst support for the removal of tritium in CANDU. To evaluate the effect of solvent on the styrene-DVB polymeric support, the solvating power dependent on various kinds and composition of solvents was calculated. In order to synthesize the macroreticular type polymer bead, the following conditions are needed; solvating power should be higher than 1 for 20% of crosslinkage and higher than 3 for 40% of crosslinkage. Stabilization of organic monomers at about $40^{\circ}C$ for more than 2 hours is prerequisite. Removal of solvent prior to drying is preferred for the post-treatment of the bead. The polymer particle size was increased by lowering concentration of surfactant and stirring speed.

• Polymer(Korea)
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• v.30 no.5
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• pp.437-444
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• 2006

Reactive hydroxypropyl methylcellulose phthalate (reactive HPMCP) was synthesized by using a stepwise urethane reaction with isophorone diisocyanate (IPDI) and 2-hydroxyethyl moth acrylate (HEMA). Molecular weight, acid number, and critical micelle concentration (CMC) of the synthesized reactive HPMCP and pristine HPMCP were measured and used as a polymeric surfactant in the emulsion polymerizations of styrene. In the preparation of HPMCP-hybrid poly styrene nanoparticles, 6, 9, 12, 18, and 24 wt% of HPMCPs were introduced, and the maximum rate of polymerization ($R_{p,max}$), the average number of radicals per particle (n), particle size distribution were investigated. In addition, core - shell morphology of the nanoparticles were observed by using TEM and their thermal stabilities were measured by using TGA. Reactive HPMCP showed higher $R_{p,max}$, smaller particle size, larger values of n and gel contents as compared with pristine HPMCP, due to the vinyl groups from HEMA, which can be reacted with styrene oligomers, in the reactive HPMCP.

• Membrane Journal
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• v.27 no.2
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• pp.154-166
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• 2017

Polymeric films for gas barrier applications such as food packaging and electronic devices have attracted great interest due to their cheap, light and easy processability among gas barrier materials. Especially in electronic devices, extremely low gas permeance is necessary for maintaining the device performance. However, current polymeric barrier films still suffer from relatively high gas permeance than other materials. Therefore, there have been strong needs to enhance the gas barrier performance of polymeric barrier films while keep their own advantages. Recently, graphene is highlighted as a 2D-layered material for gas barrier applications. However, owing to the poor workability and difficulty to produce in engineering scale, graphene oxide (GO) is on the rise. GO consists of oxygen-containing functional groups on surface with intrinsic 2D-layered structure and high aspect ratio, and it can be well-dispersed in aqueous polar solvents like water, resulting in scalable mass production. Here, we prepared GO incorporated polyimide (PI) nanocomposites. PI is widely used barrier polymer with high mechanical strength and thermal and chemical stability. We demonstrated that PI/GO nanocomposites could perform as a gas barrier. Furthermore, surfactants (Triton X-100 (TX) and Sodium deoxycholate (SDC)) are introduced to enhance the gas barrier performance by improving the degree of dispersion of GO in PI matrix. As a result, TX enhanced the gas barrier performance of PI/GO nanocomposites which is similar to predicted value. This finding will provide new insight to polymer nanocomposites for gas barrier applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1552-1555
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• 2005

We have studied the inkjet patterning of synthesized aqueous silver nano-sol on interface-controlled ITO glass substrate. Furthermore, we designed the conductive ink for direct inkjet patterning on bare ITO glass substrate. The first, the highly concentrated polymeric dispersant-assisted silver nano sol was prepared by variation of molecular weight and control of initial nucleation and growth of silver nanoparticles. The high concentration of batch-synthesized silver nano sol was possible to 40 wt%. At the same time the particle size of silver nanoparticles was below $10{\sim}20nm$. The second, the synthesized silver nano sol was inkjet - patterned on ITO glass substrate. The connectivity and width of fine line depended largely on the wettability of silver nano sol on ITO glass substrate, which was controlled by surfactant. The relationship was understood by wetting angle. The fine line of silver electrode as fine as $50{\sim}100\;{\mu}m$ was successfully formed on ITO glass substrate. The last, the direct inkjet-patternable silver nano sol on bare ITO glass substrate was designed also.

• Composites Research
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• v.29 no.5
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• pp.269-275
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• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.397-402
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• 2007

Restenosis after percutaneous coronary intervention (PCI) continues to be a serious problem in clinical cardiology. To solve this problem, drug eluting stents (DES) with antiproliferative agents have been developed. Variable local drug delivery systems in the context of stenting require the development of stent manufacture, drug pharmacology and coating technology. We have worked on a system that integrates electrophoretic deposition (EPD) technology with the polymeric nanoparticles in DES for local drug delivery and a controlled release system. The surface morphology and drug loading amount of DES by EPD have been investigated under different operational conditions, such as operation time, voltage and the composition of media. We prepared poly-D,L-lactide-co-glycolic acid (PLGA) nanoparticles embedded with curcumin, which was done by a modified spontaneous emulsification method and used polyacrylic acid (PAA) as a surfactant because its carboxylic group contribute negative charge to the surface of CPNPs (?53.5 ± 5.8 mV). In the process of ‘trial and error' endeavors, we found that it is easy to control the drug loading amount deposited onto the stent while keeping uniform surface morphology. Accordingly, stent coating by EPD has a wide application to the modification of DES using various kinds of nanoparticles and drugs.

• Carbon letters
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• v.13 no.4
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• pp.191-204
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• 2012

Carbon nanotubes (CNTs) have exceptional mechanical, electrical, and thermal properties compared with those of commercialized high-performance fibers. For use in the form of fabrics that can maintain such properties, individual CNTs should be held together in fibers or made into yarns twisted out of the fibers. Typical methods that are used for such purposes include (a) surfactant-based coagulation spinning, which injects a polymeric binder between CNTs to form fibers; (b) liquid-crystalline spinning, which uses the nature of CNTs to form liquid crystals under certain conditions; (c) direct spinning, which can produce CNT fibers or yarns at the same time as synthesis by introducing a carbon source into a vertical furnace; and (d) forest spinning, which draws and twists CNTs grown vertically on a substrate. However, it is difficult for those CNT fibers to express the excellent properties of individual CNTs as they are. As solutions to this problem, post-treatment processes are under development for improving the production process of CNT fibers or enhancing their properties. This paper discusses the recent methods of fabricating CNT fibers and examines some post-treatment processes for property enhancement and their applications.

• Journal of the Korean Chemical Society
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• v.47 no.5
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• pp.479-486
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• 2003

In this study, poly(DL-lactide-co-glycolide) nanoparticles loaded with water-insoluble vitamins such as vitamin A (Retinol) and vitamin E acetate were prepared by the emulsification diffusion method. Polymer solution was prepared by the two water-miscible organic solvent, such as ethanol and acetone. Because of its biocompatible property, polyethyleneglycol-polypropyleneglycol diblock copolymer was used as surfactant and stabilizer. The influence of some preparative variables on the nanoparticle formation and on the loading efficiency of active agents, such as the type and concentration of stabilizing agent, the stirring methods, the water/oil phase ratio and the polymer concentration were investigated in order to control and optimize the process. After preparation of nanoparticles loaded with active agent, particle size and distribution were evaluated by the light scattering particle analyzer. The loading efficiency of active agents was evaluated by the UV-visible spectroscopy. As the results, particle size were 50-200 nm and dispersibility was monodisperse. The optimum loading efficiency of active agents was observed 50-60%. It was found that the appropriate of selections of binary solvent mixtures and polymeric concentrations in both organic and aqueous phases could provide good yield and favorable physical properties of PLGA nanoparticles.