• Title/Summary/Keyword: 분자간력

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Morphology and Tensile Properties of Polyimide/Polyamideimide Composites from Different Polyimide Precursors (Polyimide 전구체에 따른 Polyimide/Ppolyamideimide 복합체의 형태학 및 인장 특성)

  • 김진봉;최윤희;임병탁;박준상
    • Polymer(Korea)
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    • v.25 no.2
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    • pp.160-167
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    • 2001
  • The various compositions of polyimide (PI)/polyamideimide (PAI) composites were prepared by heat treatment of the solvent cast PI precursors/PAI blends. The optical micrographs showed that a good compatibility was observed between poly(amic acid) (PAA) and PAI, but in the case of PAME/PAI mixtures, a phase separation apparently occurred due to the absence of ionic and/or H-bonding forces. Regardless of PI precursors, the similar tensile properties were observed. The tensile modulus of the composites were higher than that of the neat polyimide. The X-ray diffraction patterns of the composites showed that the chain rearrangement of PI was increased due to the plasticizing effect of PAI, which has lower glass transition temperature than that of PI, during thermal imidization process.

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A Study on the Preparation and Dielectric Characteristic of $\beta$-PVDF Vapor Deposited Thin Films by Applied Electric Field Method (전계인가법을 이용한 $\beta$-PVDF 증착 박막의 제조와 유전특성에 관한 연구)

  • 박수홍;이덕출
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.3
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    • pp.221-228
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    • 1998
  • In this study, the $\beta$-Polyvinylidene fluoride(PVDF) thin films were fabricated by physical vapor deposition method. Also, the properties of dielectric relaxation were studied to understand carrier's behavior of PVDF thin films, to be regarded as the excellent piezo and pyroelectricity. In the process of vapor deposition, the $\beta$-PVDF thin films have been fabricated under the condition of the substrate temperature at 3$0^{\circ}C$, the applied electric field at 142.8kV/cm and the pressure at 2.0${\times}10^{-5}$torr. The dielectric properties of PVDF have been studied in the frequency range 10Hz to 1MHz at temperature from 30 to $100^{\circ}C$. The relative dielectric constant of $\alpha$ and $\beta$-PVDF were 6.8 and 9.8, respectively, under a frequency of 1kHz. Such a phenomenon was caused by the decrease in intermolecular forces originated by the phase-transition from the TGTG' molecular conformation to the TT planar zig-zag conformation. And the relative dielectric constant is increased as a measuring temperature increases, because of the reduction of relaxation time caused by the decrease of intermolecular force.

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Molecular Dynamics Simulations of Fullerene Nanostructure Fabrications by Atomic Force Microscope Carbon Nanotube tip (원자간력 현미경 탄소 나노튜브 팁을 이용한 플러렌 나노 구조물 제작에 관한 분자동역학 시뮬레이션)

  • 이준하;이홍주
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.8
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    • pp.812-822
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    • 2004
  • This paper shows that carbon nanotubes can be applied to a nanopipette. Nano space in atomic force microscope multi-wall carbon nanotube tips is filled with molecules and atoms with charges and then, the tips can be applied to nanopipette when the encapsulated media flow off under applying electrostatic forces. Since the nano space inside the tips can be refilled, the tips can be permanently used in ideal conditions of no chemical reaction and no mechanical deformation. Molecular dynamics simulations for nanopipette applications demonstrated the possibility of nano-lithography or single-metallofullerene-transistor array fabrication.

The Spreading Characteristics of the (Polymer/18-Crown-6) Composite Solution for Water Cast-Membranes ((Polymer/18-Crown-6)복합박막 제조용액의 수면전개 특성)

  • 남석태;최호상;최성부;김병식
    • Membrane Journal
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    • v.6 no.4
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    • pp.265-272
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    • 1996
  • The (polymer/carrier) composite membranes for separating the metallic ion have been prepared by the water cast-method. The morphology of these membranes was affected by the physical properties of the spreading solution. The surface tension of the (polymer/18-crown-6) composite solution was decreased with increasing the concentration of 18-crown-6 compound and the surface tension of polymer solution decreased the following order PVC>PS>CA. The viscosity of CA solution decreased with increasing the contents of the 18-crown-6 compound, but PVC and PS solutions showed no significance changes according as the concentration of 18-crown-6 compound. In the composite solutions, the spreading ability was improved by' the cyclic 18-crown-6 molecules which acted as an electric buffer and diminished the intermolecular force between the polymer chains. The (polymer/18-crown-6) composite membrane was more uniform than that of the mono polymer membrane on the coagulation state of polymer, and the top and bottom sides of membrane showed also the more smooth structure according as the concentration increment of 18-crown-6 molecule.

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The Rheological Properties of Poly(acrylonitrile)/Cellulose Acetate Blend Solutions in N,N-Dimethyl Formamide (폴리아크릴로니트릴/셀룰로오스 아세테이트/N,N-디메틸포름아미드 용액의 유연학적 특성)

  • Park, Seung-Han;Song, In-Kyu;Kim, Byoung-Chul
    • Polymer(Korea)
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    • v.33 no.4
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    • pp.384-388
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    • 2009
  • The rheological properties of poly (acrylonitrile) (PAN) and cellulose acetate (CA) blend solutions in N,N-dimethyl formamide (DMF) were investigated in terms of temperature and blend composition. The solutions exhibited a very characteristic rheological behavior with variation of temperature. 8 wt% solution showed an increase of viscosity and a decrease of loss tangent as temperature was increased over the temperature range of 20 and $60^{\circ}C$. At $20^{\circ}C$ the physical properties of the solutions exhibited dependence on the blend composition. At 40 and $60^{\circ}C$, however, the effects of blend ratio on the physical properties notably diminished. The longer relaxation time at higher temperature indicated that the formation of physical structures resulting from intermolecular interactions was promoted with increasing temperature. The odd rheological responses were further elucidated by measuring of the physical properties of dilute solutions. The intrinsic viscosity of the solutions suggested that the coiled chain dimension was reduced with increasing temperature.

Formation of parallel nanostructures by Surface-Patterning Technique for the Application to Nano-Device (나노 소자의 응용을 위한 표면 패터닝 기술을 이용한 평형한 나노구조물 형성)

  • Kim, Yu-Duk;Kim, Hyung-Jin;Hong, Byung-You
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.514-514
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    • 2007
  • 1차원 구조를 갖는 나노 와이어들은 나노 소자를 구현하기 위한 building-block으로 많은 과학자들의 주목을 받고 있고 또한 연구되고 있다. 하지만 그것을 정확하게 위치시키고 일정한 간격으로 정렬시키기 위한 기술 개발은 아직도 해결해야 할 큰 과제로 남아 있다. 이 논문에서, 우리는 ahsing 기술과 표면 패터닝 기술을 이용하여 대면적의 실리콘웨이퍼 위에 DNA(deoxyribonucleic acid)를 기반으로 한 금 나노 와이어를 정확하게 위치시키고 일정한 간격으로 정렬시킬 수 있는 새로운 제어 기술을 제안한다. 먼저 우리는 포토 리소그래피 공정과 $O_2$ 플라즈마 ashing 기술을 이용하여 선폭을 100 nm로 감소 시켰다. 그리고 자기조립단분자막 (self-assembled monolayers; SAMs) 방법과 lift-off 공정을 반복함으로서 1-octadecyltrichlorosilane(OTS) 층과 aminopropylethoxysilane(APS) 층을 형성하였다. 마지막으로 DNA 용액을 샘플 표면 위에 도포하고 분자 빗질 방법으로 DNA를 한 방향으로 정렬 시켰고 금 나노입자 용액을 처리하였다. 그 결과 금 나노 와이어는 $10{\mu}m$ 간격으로 일정하게 정열 되었고, APS 층에만 정확하게 정렬되었다. 우리는 금 나노 와이어를 관찰하기 위하여 원자간력 현미경 (Atomic Force Microscope AFM)을 사용하였다.

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Self-healing Engineering Materials: I. Organic Materials (자기치유 공학재료: I. 유기 재료)

  • Choi, Eun-Ji;Wang, Jing;Yoon, Ji-Hwan;Shim, Sang-Eun;Yun, Ju-Ho;Kim, Il
    • Clean Technology
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    • v.17 no.1
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    • pp.1-12
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    • 2011
  • Scientists and engineers have altered the properties of materials such as metals, alloys, polymers, ceramics, and so on, to suit the ever changing needs of our society. Man-made engineering materials generally demonstrate excellent mechanical properties, which often tar exceed those of natural materials. However, all such engineering materials lack the ability of self-healing, i.e. the ability to remove or neutralize microcracks without intentional human interaction. The damage management paradigm observed in nature can be reproduced successfully in man-made engineering materials, provided the intrinsic character of the various types of engineering materials is taken into account. Various self-healing ptotocols that can be applied for the organic materials such as polymers, ionomers and composites can be developed by utilizing suitable chemical reactions and physical intermolecular interactions.

Synthesis and Characterization of Polymers with Azobenzene and Hexamethylene Groups in Main Chain (주사슬에 아조벤젠기와 헥사메틸렌기를 갖는 고분자의 합성 및 특성)

  • Gu, Su-Jin;Lee, Eung-Jae;Bang, Moon-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.86-92
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    • 2019
  • Polymers with various compositions of azobenzene and hexamethylene groups in the main chain were synthesized by a Schotten-Baumann reaction and their properties were investigated. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and x-ray diffraction. The polymers showed an inherent viscosity of 1.28-1.36 dl/g and were relatively insoluble in most organic solvents. The melt transition temperature increased rapidly with increasing number of azobenzene groups in the polymer. When the azobenzene monomer content was more than 50 mol%, no melting transition occurred below the decomposition temperature. Among the polymers with a melt transition temperature, the MP-A3C7 and MP-A5C5 polymers were liquid crystalline materials and exhibited a nematic phase with weak liquid crystallinity over a wide liquid crystal temperature range. This difference in the properties of the synthesized polymers is likely due to the changes in intermolecular forces resulting from the linearity and polarity of the trans-form of azobenzene.

Second harmonic generation of pulsed corona - poled nonlinear optical polymer films (펄스 corona 배향된 비선형광학 고분자박막의 제2 고조파발생)

  • Kim, Jun-Soo;Lee, Jong-Ha;Lee, Hwang-Un;Kim, Sang-Youl;Won, Young-Hee
    • Korean Journal of Optics and Photonics
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    • v.13 no.4
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    • pp.356-362
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    • 2002
  • The molecular orientational dynamics of the nonlinear optical(NLO) side-chain polymer N-(4-nitrophenyl)-(L)-prolinol-poly (pphenylene terephthalates) have been studied using nonlinear optical responses as measured by second harmonic generation (SHG). A new pulsed corona poling is used to orient the NLO chromophores and the polymer segments into the noncentrosymmetric structure required to obtain the SHG signal. By corona poling of negative high voltage pulses with variable repetition rates (between 0.5 and 10 ㎑) at temperature between 25$^{\circ}C$ and 80$^{\circ}C$, well below and about the glass transition temperature 70$^{\circ}C$, the side-chain chromophores and the polymer chain contour rearrange themselves and create the domain structure observed by atomic force microscopy(AFM). The pulsed corona voltage enhances the orientational ordering of the NLO chromophores and also significantly influences the growth of SHG signal and the improved relaxation behavior after the poling field is removed, reducing the visible damage to the polymer film dramatically. This new pulsed corona poling experiment gave direct in situ evidence that the NLO chromophore and the polymer backbone undergo anisotropic rearrangement during the poling process.