• Journal of Adhesion and Interface
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• v.9 no.4
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• pp.30-33
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• 2008

Two polymeric interfaces with single component homo-polymers were prepared to control the orientation of block copolymer thin-film nanostructures. Poly(4-acetoxy styrene) (OH-PAS) and poly(4-methoxy styrene) (OH-PMS) which have the average chemical composition of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) were precisely synthesized through nitroxide-mediated radical polymerization. After dehydration reactions between above polymers and SiOx layers of silicon wafers, the polymer-modified interface induced partial (30%) vertical orientation of PS-b-PMMA thin film in the case of OH-PMS and wholly parallel orientation in the case of OH-PAS. Chemical compositions of polymeric interface layers are regarded as the key parameter to control the orientation of nanostructures of block copolymer thin film.

• Polymer(Korea)
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• v.37 no.6
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• pp.744-752
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• 2013

The miscibility between poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) was investigated using thermal analyses for the purpose of developing birefringence-free material at oriented state. The effect of methyl acrylate (MA) units as comonomer of PMMA on the miscibility was also studied. All the blends prepared in this study show composition-dependent single $T_g$'s between those of blend components and high transparency over the visible region, indicating the miscibility at molecular level and no discernible effect of MA units on it. No phase separation was observed at elevated temperature of $280^{\circ}C$, higher than the degradation of PLLA and PMMA. The interaction energy density in PLLA/PMMA blends with 17 mol% of MA was measured to be $-0.74J/cm^3$ from the equilibrium melting temperature depression based on the Hoffman-Weeks method. The blends show zero-${\Delta}$n behavior at a specific mixing ratio and the drawing ratio of 3 due to compensation of intrinsic orientation birefringence. Birefringence dispersion of PLLA/PMMA5 blends was also measured to examine the possibility for quarter-wave plates or polarizer protective films.

• Membrane Journal
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• v.9 no.3
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• pp.151-156
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• 1999

Silicone was used in this study to enhance the oxygene permeability of gas separation membranes. PMP and PMMA were used to prepare the copolymers and IPN membranes, respectively. In the case of copolymers, there were two methodsCswelling and solvent evaporation) in this study and it was revealed that this preparation method affected the oxygene permeability. It was also shown that the IPN method brought the enhacement of oxygen permeability and slight decrease of separation factor. Regarding oxygen permeability 10 wt% of PMMA was the best composition of IPN membrane.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.231-237
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• 2014

The supercritical fluids (SCFs) have been widely used for material synthesis and processing due to their remarkable properties including low viscosity, high diffusivity and low surface tension. Carbon dioxide is one of the suitable solvents in SCFs processes in terms of its advantages such as easy processibility (with low critical temperature and pressure), inexpensive, nonflammable, nontoxic, and readily available. However, it has generally low solubility for high molecular weight polymers with the exception of fluoropolymers and siloxane polymers. Therefore, hydrocarbon solvents and hydrochlorofluorocarbons have been used for various SCFs process by its high solubility for high molecular weight polymers. In this report, a PMMA/clay nanocomposites were fabricated by using supercritical fluid process. The $Na^+$-MMT(montmorillonites)was modified by a fluorinated surfactant which is able to enhance compatibility with the chlorodifluoromethane(HCFC-22) and thus, improve dispersability of the clay in the polymer matrix. The PMMA/fluorinated surfactant modified clay nanocomposite shows enhanced mechanical and thermal properties which characterized by X-raydiffraction(XRD), Thermo gravimetric analysis(TGA), Dynamic mechanical analysis (DMA) and Transmission electron microscopy (TEM).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.19-23
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• 2019

The PMMA (polymethyl methacrylate)/clay nanocomposites were synthesized by in situ radical polymerizations with different clay contents (3 and 7 wt%) using microwave heating. The nanostructure, optical, and thermal properties of the synthesized PMMA/clay nanocomposites were measured by XRD, TEM, AFM, UV-vis, and TGA. It was found that the intercalated- or exfoliated structure of PMMA/clay nanocomposites was strongly dependent on the content of clay. Thus, the imposition of microwave-assisted polymerization facilitated a delamination process of layered silicates to achieve exfoliation state of interlayer distance. The PMMA/3 wt% C10A nanocomposite with well-dispersed and exfoliated clay nano-layers showed the good optical transparency similar to pure PMMA in this study. The thermal decomposition rates of the PMMA/clay nanocomposites become to be lower compared to that of the pure PMMA, indicating the intercalated- or exfoliated inorganic silicate has high thermal stability. A possible reason is that the thermally segmental motion of PMMA polymer into inorganic silicate interlayer spacing has increased the thermal stability of the PMMA/clay nanocomposites.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.41-47
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• 2012

Multi-walled carbon nanotubes (MWCNTs) incorporated polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) nanofibers were synthesized using electronspinning method. Effects of polymer concentration and applied voltage on the synthesis of PAN and PMMA nanofibers were systematically investigated. The structural characterization of PAN/MWCNTs and PMMA/MWCNTs composited nanofibers synthesized as a function of the MWCNTs concentration was performed by scanning electron microscopy and transmission electron microscopy. 5 wt% MWCNTs incorporated PAN and PMMA electrospun nanofiber exhibit best strength and stiffness.

• Polymer(Korea)
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• v.33 no.3
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• pp.263-267
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• 2009

In order to improve the hydrophilic property on the surface of d-PMMA(deuterated poly-(methyl methacrylate)) film, it was exposed to oxygen plasma, All experimental conditions were same except to plasma exposure time that was varied from 0 to 180 s, The effects according to the exposure time were identified using contact angles, X-ray reflectometer(XRR), neutron reflectometer(NR), and X-ray photoelectron spectroscopy(XPS). By confirming that as the exposure time increases, water contact angle decreases while the composition of oxygen increases, it was confirmed that the composition of oxygen has a huge influence on improving the hydrophilic property. The physical characters as a function of the exposure time were investigated by the XRR. By analyzing complementally the results of the XRR, NR, and XPS, more detailed chemical bonding conditions were studied by obtaining not only composition of the carbon and oxygen but that of the hydrogen.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.25-31
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• 2022

By an aid of needle coating, we have fabricated a spherical microlens array using poly(methyl methacrylate) for potential applications in light extraction of organic light-emitting diodes. With an attempt to achieve high-density and high-aspect-ratio microlens arrays, we have investigated the coating behaviors by varying the material parameters such as the solute concentration and wettability of the poly(methyl methacrylate) solution and process parameters such as the dwell time of needle near the substrate, retract distance of needle from the substrate, and coating gap between the needle and substrate. Under the optimized coating conditions, it is demonstrated that high-aspect-ratio microlens arrays can be obtained using a coating solution with high solute concentration and a small amount of a hydrophobic solvent. It is found that the diameter and height of microlens array are decreased with increasing poly(methyl methacrylate) concentration, yet the overall aspect ratio is rather enhanced. By the addition of 5 wt% hexylamine in 35 wt% poly(methyl methacrylate) solution, we have achieved a spherical microlens with the height of 7.7 ㎛ and the width of 94.24 ㎛ (the aspect ratio of 0.082). To estimate the capability of light extraction by the microlens array, we have performed ray tracing simulations and demonstrated that the light extraction efficiency of organic light-emitting diode is expected to be enhanced up to 24%.

• Macromolecular Research
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• v.13 no.3
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• pp.206-211
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• 2005

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be $3 wt\%$ of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.378-378
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• 2012

나노복합체를 이용하여 제작한 유기 쌍안정성 형태의 비휘발성 메모리 소자는 간단한 공정과 플렉서블 기기에 응용 가능성 때문에 많은 연구가 진행되고 있다. 나노복합체를 사용하여 제작한 비휘발성 메모리 소자의 전기적 성질에 대한 연구는 많이 진행되었으나, poly (methyl methacrylate) (PMMA) 고분자 박막 내부에 분산된 $SnO_2$ 나노입자를 이용하여 제작한 유기 쌍안정성 소자에서 기억 특성의 안정성에 대한 연구는 상대적으로 미흡하다. 본 연구에서는 PMMA 박막층 내부에 분산된 $SnO_2$ 나노입자를 사용한 메모리 소자를 제작하여 전기적 특성 및 안정성에 대하여 관찰하였다. $SnO_2$ 나노입자를 PMMA와 용매인 클로로벤젠에 용해한 후에 초음파 교반기를 사용하여 두 물질을 고르게 섞었다. 전극이 되는 indium-tin-oxide 가 성장된 유리 기판 위에 $SnO_2$ 나노입자와 PMMA가 섞인 용액을 스핀 코팅한 후, 열을 가해 용매를 제거하여 SnO2 나노입자가 PMMA에 분산되어 있는 유기 쌍안정성 형태의 나노복합체 박막을 형성하였다. 형성된 나노복합체 박막 위에 상부 전극으로 Al을 열증착하여 비휘발성 메모리 소자를 제작하였다. 제작된 소자의 전류-전압 측정 결과는 메모리 특성을 나타내는 ON과 OFF의 두 가지 상태가 존재하고 ON/OFF 전류 비율은 20이었다. $SnO_2$ 나노입자를 포함하지 않은 소자와 비교를 통해 $SnO_2$ 나노입자가 비휘발성 메모리 소자에서의 전하 저장 영역으로 하는 역할을 확인하였다. 전류-시간 측정 결과 소자의 ON/OFF 전류 비율이 시간에 따라 큰 변화 없이 1,000회 이상 지속적으로 유지함을 관찰함으로써 소자의 안정성을 확인하였다.