• 한국응용과학기술학회지
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• 제17권4호
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• pp.257-261
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• 2000

Monodisperse polymer particles have many industrial applications such as surface coatings for metal panels, chromatographic media, spacers for liquid crystal display panel, and fillers for cosmetics, etc.. Micron-size monodispersed poly(methyl methacrylate) particles were prepared by dispersion polymerization in methanol medium in the presence of poly(vinyl pyrrolidone) and 2,2'-azobis(isobutyronitrile) as steric stabilizer and initiator, respectively. Effects of polymerization parameters, such as monomer and initiator concentration, stabilizer type and concentration, solvent composition on average particle size and size distribution were studied.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2245-2248
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• 2009

This paper demonstrates room temperature chemical vapor deposition (RTCVD) for fabricating titania inverse opals. The colloidal crystals of monodisperse polymer latex spheres were used as a sacrificial template. Titania was deposited into the interstices between the colloidal spheres by altermate exposures to water and titanium tetrachloride (Ti$Cl_4$) vapors. The deposition was achieved under atmospheric pressure and at room temperature. Titania inverse opals were obtained by burning out the colloidal template at high temperatures. The filling fraction of titania was controlled by the number of deposition of Ti$Cl_4$ vapor. The morphology of inverse opals of titania were investigated. The optical reflection spectra revealed a photonic band gap and was used to estimate the refractive index of titania.

• Korea-Australia Rheology Journal
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• 제13권1호
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• pp.29-35
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• 2001

The development of filament stretching extensional rheometers over the past decade has enabled the systematic measurement of the transient extensional stress growth in dilute and semi-dilute polymer solutions. The strain-hardening in the extensional viscosity of dilute solutions overwhelms the perturbative effects of capillarity, inertia & gravity and the kinematics of the extensional deformation become increasingly homogeneous at large strains. This permits the development of a robust open-loop control algorithm for rapidly realizing a deformation with constant stretch history that is desired for extensional rheometry. For entangled fluids such as concentrated solutions and melts the situation is less well defined since the material functions are governed by the molecular weight between entanglements, and the fluids therefore show much less pronounced strain-hardening in transient elongation. We use experiments with semi-dilute/entangled and concentrated/entangled monodisperse polystyrene solutions coupled with time-dependent numerical computations using nonlinear viscoelastic constitutive equations such as the Giesekus model in order to show that an open-loop control strategy is still viable for such fluids. Multiple iterations using a successive substitution may be necessary, however, in order to obtain the true transient extensional viscosity material function. At large strains and high extension rates the extension of fluid filaments in both dilute and concentrated polymer solutions is limited by the onset of purely elastic instabilities which result in necking or peeling of the elongating column. The mode of instability is demonstrated to be a sensitive function of the magnitude of the strain-hardening in the fluid sample. In entangled solutions of linear polymers the observed transition from necking instability to peeling instability observed at high strain rates (of order of the reciprocal of the Rouse time for the fluid) is directly connected to the cross-over from a reptative mechanism of tube orientation to one of chain extension.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1345-1348
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• 2010

Highly monodisperse polystyrene (PS) nanospheres were fabricated by surfactant-free emulsion polymerization in water using styrene, 2,2'-azobis(2-methyl propionamidine) dihydrochloride (AIBA), and poly(vinyl pyrrolidone) (PVP). The size and distribution of the PS nanospheres were systematically investigated in terms of initiator concentration, stabilizer concentration, reaction temperature, reaction time, and reactant concentration. With increasing AIBA initiator concentration, PS particle sizes are raised proportionally, and can be controlled from 120 to 380 nm. Particle sizes were reduced with increasing PVP concentration. This decrease occurs because a high PVP concentration leads to a large number of primary nuclei in the early stage of polymerization. When the reaction temperature increased, the sizes of the PS particles decrease slightly. The particles grew quickly during the initial reaction stage (1-3 h) and the growth rate became steady-state after 6 h. The PS sizes approximately doubled when the reactant (styrene, PVP, azo-initiator) concentrations were increased by a factor of eight.

• 공업화학
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• 제5권6호
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• pp.1009-1015
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• 1994

분산중합으로 합성한 폴리스티렌 seed를 사용하여 seed 중합방법으로 단분산성인 다공성 스티렌-디비닐벤젠(St-DVB) 겔과 아크릴로니트릴-에틸렌 디메타크릴레이트(AN-EDMA) 겔을 제조하였다. 합성한 St-DVB 겔과 AN-EDMA 겔은 HPLC용 충진제로 적합한 좁은 입도분포와 다공성을 갖고 있으며, 이들 겔을 충진한 GPC 또는 HPLC용 column은 비교적 높은 효율을 나타내었다, 또한 AN-EDMA 겔을 아미드옥심화한 AAN-EDMA 겔에 대한 $Cu^{2+}$, $Cd^{2+}$ 및 ${UO_2}^{2+}$ 이온의 흡착특성을 시험하였다.

• Macromolecular Research
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• 제12권4호
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• pp.384-390
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• 2004

Single-walled carbon nanotubes (SWNTs) have been chemically modified through the formation of carboxylic acid functionalities or by grafting octadecylamine and polystyrene onto them. We purified SWNTs with nitric acid to remove some remaining catalysts and amorphous carbon materials. After purification, we broke the carbon nanotubes and shortened their lengths by using a 3:1 mixture of concentrated sulfuric acid and nitric acid. During these purification and cutting processes, carboxylic acid units formed at the open ends of the SWNTs. Octa-decylamine and amino-terminated polystyrene were grafted onto the cut SWNTs by condensation reactions between the amine and carboxylic acid units. The cut SWNTs did not disperse in organic solvents, but the octadecylamine-grafted and polystyrene-grafted SWNTs dispersed well in dichloromethane and aromatic solvents (e.g., benzene, toluene). Composites were prepared by mixing polystyrene with the octadecylamine-grafted or polystyrene-grafted SWNTs. Each composite had a higher dynamic storage modulus than that of a pristine polystyrene. The composites exhibited enhanced storage moduli, complex viscosities, and unusual non-terminal behavior when compared with a monodisperse polystyrene matrix because of the good dispersion of carbon nanotubes in the polystyrene matrix.

• Macromolecular Research
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• 제12권5호
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• pp.512-518
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• 2004

We have synthesized a novel macromonomer of vinyl-terminated bifunctional polyurethane having a molecular weight of 37,000 g/mol and successfully applied it to the dispersion polymerization of methylmethacrylate(MMA). We verified the presence of the vinyl terminal group and the macromonomer grafted onto the poly(ethylene glycol)(PEG) block in the PMMA particles by using $^1$H and $\^$13/C NMR spectroscopies. Monodisperse PMMA microspheres that have good uniformity of 1.01 were prepared at 20 wt% macromonomer content; we investigated the characteristics of the PMMA particles in terms of their molecular weight, molecular weight distribution, size of the particles, thermal properties, and glass transition temperature. We have found that the synthesized polyurethane macromonomer is an effective stabilizer.

• 폴리머
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• 제33권5호
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• pp.463-468
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• 2009

입자 분포가 균일하며, 마이크론 크기를 가지는 중공 유기 안료에 대한 합성 방법을 연구하였다. 코어-쉘 합성 방법에 의해 다양한 크기의 중공 유기 안료를 합성할 수 있었으며, 각각의 코어 크기 및 분자량에 따른 최종 입자 크기 변화 및 반응 중 코어의 중화 시간에 따른 은폐율 변화에 대한 실험을 진행하였다. 그 결과 사용한 코어 크기가 클수록 최종 입자 크기는 증가되며, $1.0{\mu}m$ 이상의 마이크론 크기를 가지는 중공 유기 안료를 합성하기 위해서는 적어도 200 nm 이상의 코어를 사용해야 함을 알 수 있었다. 또한, 사용한 코어 크기가 클수록 중공 부피비가 증가되나, 은폐율을 높이기 위해서는 코어의 분자량을 줄이거나, 코어의 알카리 팽윤 단계에서 중화 시간을 증가시켜 주어야 한다. 그리고, 반응 중 교반 속도 및 합성 고형분이 마이크론 크기의 중공 유기 안료 합성에 끼치는 영향을 알아보았다.

• Korean Chemical Engineering Research
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• 제45권5호
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• pp.493-499
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• 2007

본 연구에서는 UV photo-lithography 방식의 particle replication in non-wetting templates(PRINT) 법을 이용하여 약물 전달에 운반체로 사용되는 $3{\mu}m{\times}3{\mu}m{\times}2{\mu}m$ 사이즈의 균일한 고분자 하이드로젤 입자를 제조하였다. 몰드(mold)와 기재(substrate)는 PRINT 방식을 통하여 탄성을 지닌 perfluoropolyethers(PFPE)로 제작하였으며 이를 반복적으로 사용할 수 있도록 하였다. 제작된 입자는 점착성이 있는 수용성 고분자를 이용하여 회수하였다. 입자의 주요 성분은 생분해성 고분자인 poly(ethylene glycol) diacrylate(PEG-diA)이며, 세포 uptake에 적합하도록 aminoethylacrylate(AEM)와 2-acryloxyethyltrimethyl ammonium chloride(AETMAC)를 첨가하였다. 본 연구를 통해 균일하고 원하는 크기의 생체분해성 고분자 입자를 제작하는 PRINT 기술이 약물 전달 및 유전자 전달에 필요한 수송체인 비바이럴 벡터를 제작하기 위한 효과적인 기술임을 제시하였다.

• 폴리머
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• 제33권1호
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• pp.33-38
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• 2009

은 카바메이트 착체 화합물의 환원에 의한 무전해 도금법으로 은/폴리스티렌 비드를 제조하기 위하여 폴리스티렌 및 아민 관능기를 가지는 공중합체 비드를 제조하였다. 스티렌, divinylbenzene(DVB) 그리고 2-(N,N-dimethylamino)ethyl methacrylate (DAEMA) 단량체들을 poly(vinyl alcohol) 존재 하에서 물/메탄올을 용매로 사용하여 무유화중합을 진행하였다. 30/0$\sim$1.5/0$\sim$3 wt%의 단량체 조성을 가지는 poly(styrene/DVB/DAEMA) 비드는 구형으로 1 ${\mu}m$의 일정한 크기를 가지고 있었다. 아민 기능기를 가지는 폴리스티렌 비드의 무전해 도금은 비드의 전처리 없이 silver 2-ethylhexylcarbamate (Ag-EHCB) 복합체와 히드라진 환원제를 사용하여 메탄올 용액에서 진행하였다. 제조된 비드와 도금된 비드 표면의 형태를 SEM으로 관찰하였으며 은 도금된 비드를 분산시켜 자외선 흡수 변화 그리고 도금된 은의 성분을 XRD로 분석하였다.