• Title/Summary/Keyword: hexafluoroisopropylidene

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Synthesis and Characterization of Transparent Copolyimide Films (II) (투명한 공중합체 폴리이미드 필름의 합성 및 특성 연구(II))

  • Park, Jong-Su;Chang, Jin-Hae
    • Polymer(Korea)
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    • v.33 no.4
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    • pp.313-318
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    • 2009
  • Copolyimides were synthesized from bis (3-aminophenyl) sulfone (APS) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) containing a fluorine substituent ($-CF_3$) with different mole ratios of 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA) containing a sulfone group (-$SO_2$-). The PI films were obtained from poly (amic acid) (PAA) by solution casting through thermal imidization on a glass plate. Wide-angle X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal tensile machine (UTM) measurements, and UV-Vis spectrometry were used to assess thermo-mechanical properties, morphology, and optical transparency. Thermal properties and optical transparency decreased with increasing DSDA mole fraction. In contrast, mechanical properties increased with increasing DSDA mole fraction. As compared to conventional PI films, however, the PI copolymer films in this work were found to exhibit better optical transparency.

The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • v.17 no.12
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

Changes in the Optical and Thermal Properties of Low-Temperature Cured Polyimide Thin Films Using the Catalyst (촉매를 이용한 저온경화 폴리이미드 박막의 광학적/열적 특성 변화)

  • Park, Myeong-Soon;Kim, Kwang-In;Nam, Ki-Ho;Han, Haksoo
    • Applied Chemistry for Engineering
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    • v.24 no.3
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    • pp.320-326
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    • 2013
  • In this study, various polyimide films were synthesized via low temperature cure in order to understand changes in their physical properties when using 4,4'-oxydianiline (ODA) as a diamine and dianhydride molecules with different backbones on a single diamine such as 4,4'-Oxydiphthalic anhydride (ODPA), 4,4-hexafluoroisopropylidene diphthalic dianhydride (6FDA), and 3,3', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA). After the synthesis of poly(amic acid), polyimide films were fabricated by adding 1,4-diazabicyclo [2.2.2]octane (DABCO), a low-temperature catalyst, at various wt% to poly(amic acid)s. Changes of optical and thermal properties were compared and analyzed between polyimide films without catalyst and polyimide films with catalyst by FT-IR, UV-Vis transmittance, DSC/TGA, and WAXD analysis. Wide-angle X-ray diffraction (WAXD) analysis revealed that the mean intermolecular distance decreased with the use of a catalyst by the type of dianhydride. Thus, while the optical properties of the films improve by a low-temperature cure performed using a catalyst, their thermal properties decrease. These changes can be explained by the changes in the morphological structure of the films triggered by a catalyst-induced reduction in the mean intermolecular distance. Moreover, the results show that the type of dianhydride determines the degree of change in the optical and thermal properties in each types of polyimide, demonstrating that changes in the optical and thermal properties are directly associated with the backbone of the polyimide structure.

Gas Separation Properties of Polyaniline/Polyimide Blend Membranes (Polyaniline/Polyimide 혼합막의 기체 분리 특성)

  • Lee, Ki-Seob;Kim, Jin-Hwan
    • Applied Chemistry for Engineering
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    • v.18 no.5
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    • pp.483-489
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    • 2007
  • Polyaniline (PANI)/Polyimide (PI) membranes were prepared and the effects of PANI contents and doping on the structural properties and gas separation properties were studied. The polyamic acid (PAA) solution was prepared by the polycondensation reaction of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4'-oxydianiline (ODA) in 1-methyl-2-pyrrolydinone (NMP) solvent. The PANI/PI blends were obtained by mixing PAA solution and PANI solution, and were doped with 1 M aqueous HCl solution for 24 h. The structural characterizations of the as-cast and doped membranes were examined by FT-IR, XRD, and TGA. The gas permeation experiments with $H_2$, $CO_2$, $O_2$, $N_2$, and $CH_4$ were carried out by variable pressure method at $30^{\circ}C$ and 5 atm. For all gases tested, the permeability coefficients of the blends decreased with increasing PANI content and the magnitude of permeability was in the order of $H_2$ > $CO_2$ > $O_2$ > $N_2$ > $CH_4$. The permeability for PANI/PI membranes decreased after the doping process while the permselectivity increased. For $H_2/CH_4$ separation, the doped PANI/PI (75/25) membrane has a permselectivity of 991.

Pervaporation Separation of Trace Toluene from Water Using Hydrophobic Copolyimide Membranes (소수성 폴리이미드공중합체 막에 의한 저농도 톨루엔함유 수용액의 투과증발분리)

  • Kim, Jeong-Hoon;Chang, Bong-Jun;Lee, Soo-Bok
    • Membrane Journal
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    • v.17 no.4
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    • pp.287-293
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    • 2007
  • Pervaporation separation of toluene from water were studied using hydrophobic copolyimide membranes. The copolyimide membranes were prepared from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and two diamines (polysiloxane diamine (SIDA)/2-(perfluorohexyl) ethyl-3,5-diaminobenzene (PFDAB)). The pervaporation properties for toluene/water were investigated in terms of mol ratio of SIDA/PFDAB in polyimide membranes. Sorption- and diffusion-related properties were measured to analyze the permeation properties in solution-diffusion theory, It was found that as the SIDA content in the membranes increased, sorption of toluene and sorption selectivity of toluene/water increased due to high affinity of siloxane moiety toward toluene. Diffusion coefficient of toluene and diffusion selectivity of toluene/water also increased with SIDA content due to high free volume of siloxane moiety. As the results, the permeation flux and pervaporation selectivity increased markedly from 0.005 $kg/m^2h$ to 049 $kg/m^2h$ and from 9 to 6380, respectively.

Residual Stress Behavior and Characterization of Polyimide Crosslinked Networks via Ring-opening Metathesis Polymerization (개환 복분해 중합을 통한 가교형 폴리이미드 박막의 잔류응력 거동 및 특성 분석)

  • Nam, Ki-Ho;Seo, Jongchul;Jang, Wonbong;Han, Haksoo
    • Polymer(Korea)
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    • v.38 no.6
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    • pp.752-759
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    • 2014
  • Crosslinked polyimides (PIs) were synthesized by reacting 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFDB) with various ratios of the cross-linkable, end-capping agent cis-1,2,3,6-tetrahydrophthalic anhydride (CDBA) via ring-opening metathesis polymerization. Residual stress behaviors were investigated in-situ during thermal imidization of the crosslinked PI precursors using a thin film stress analyzer (TFSA) by wafer bending method. The thermal properties were investigated via differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA). The optical properties were measured by ultraviolet-visible spectrophotometer (UV-vis) and spectrophotometry. All properties were interpreted with respect to their morphology of crosslinked networks. With increasing the amounts of the end-capping agent, the residual stress decreased from 27.9 to -1.3 MPa, exhibited ultra-low stress and high thermal properties. The minimized residual stress and enhanced thermal properties of the crosslinked PI makes them potential candidates for versatile high-density multi-layer structure applications.