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Subject: search.filters.subject.polyimides

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Now showing 1 - 8 of 8
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    Synthesis and characterization of soluble polyimides derived from 2,2 '-bis(3,4-dicarboxyphenoxy)-9,9 '-spirobifluorene dianhydride
    (2002-01-15)
    Reddy, DS
    ;
    Shu, CF
    ;
    Wu, FI
    ;
    應用化學系
    ;
    Department of Applied Chemistry
    The synthesis of aromatic poly(ether imide)s containing spirobifluorene units in the polymer backbone is described. 2,2'-Bis(3,4-dicarboxyphenoxy)-9,9'-spirobifluorene dianhydride, which was used as a new monomer, was synthesized with 2,2'-dihydroxy-9,9'-spirobifluorene as the starting material. In the spiro-segment, the rings of the connected bifluorene were orthogonally arranged. This bis(ether anhydride) monomer was employed in reactions with a variety of aromatic diamines to furnish poly(ether imide)s, involving an initial ring-opening polycondensation and subsequent chemically induced cyclodehydration. Excellent solubility in common organic solvents at room temperature, good optical transparency, and high thermal stability are the prominent characteristic features of these new polymers, which can be attributed to the presence of spiro-fused orthogonal bifluorene segments along the polymer chain. The glass-transition temperatures of the polyimides were 240-293 degreesC, and the 5% weight-loss temperatures were greater than 500 degreesC. (C) 2001 John Wiley & Sons, Inc.
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    Synthesis and characterization of spirobifluorene-based polyimides
    (2002-11-01)
    Chou, CH
    ;
    Reddy, DS
    ;
    Shu, CF
    ;
    應用化學系
    ;
    Department of Applied Chemistry
    The synthesis and properties of organosoluble aromatic polyimides, containing spiro-skeletal units in the polymer backbone on the basis of the spiro-diamine monomer, 2,2'-diamino-9,9'-spirobifluorene, are described. In the case of the Spiro segment, the two fluorene rings are orthogonally arranged and connected through a tetrahedral bonding carbon atom, the Spiro center. As a consequence, the polymer chain is periodically zigzagged with a 90degrees angle at each Spiro center. This structural feature minimizes interchain interactions and restricts the close packing of the polymer chains, resulting in amorphous polyimides that have good solubility in organic solvents. Compared with their fluorene-based cardo analogues, the spirobifluorene-based polyimides have an improved solubility. Furthermore, the main-chain rigidity of the polyimide appears to be preserved because of the presence of the spiro structure, which restricts the free segmental mobility. As a result, these polyimides exhibit a high glass-transition temperature (T-g's) and good thermal stability. The T-g's of these polyimides were in the range of 287-374 degreesC, and the decomposition temperatures in nitrogen for a 10% weight loss occurred at temperatures above 570 degreesC. (C) 2002 Wiley Periodicals, Inc. J Polym, Sci Part A: Polym Chem 40: 3615-3621, 2002.
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    Synthesis and characterization of soluble poly(ether imide)s based on 2,2 '-bis(4-aminophenoxy)-9,9 '-spirobifluorene
    (2003-02-01)
    Reddy, DS
    ;
    Chou, CH
    ;
    Shu, CF
    ;
    Lee, GH
    ;
    應用化學系
    A series of aromatic poly(ether imide)s containing 9,9'-spirobifluorene moieties in the main chain have been synthesized via the polycondensation of 2,2'-bis(4-aminophenoxy)-9,9'-spirobifluorene with a variety of aromatic dianhydrides. In the diamine monomer, the two aminophenoxyfluorene entities are orthogonally arranged and are connected through an sp(3) carbon atom (the spiro center). The resulting poly(ether imide)s have a polymer backbone which is periodically twisted with an angle of 90degrees at each spiro center. This structural feature, which restricts the close packing of the polymer chains and reduces inter-chain interactions, leads to amorphous poly(ether imide)s with good solubility in common organic solvents. In addition, the rigidity of the main chain of these polymers appears to be preserved due to the spiro-structure. As a result, these poly(ether imide)s exhibit a high T-g and excellent thermal stability. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    Effect of the polyimide structure and ZnO concentration on the morphology and characteristics of polyimide/ZnO nanohybrid films
    (2005-01-21)
    Hsu, SC
    ;
    Whang, WT
    ;
    Hung, CH
    ;
    Chiang, PC
    ;
    Hsiao, KN
    A series of polyimide/ZnO nanohybrid films with different ZnO content were prepared from a rigid pyromellitic dianhydride-4,4'-diaminodiphenyl ether (PMDA-ODA) polyimide (PI) and a flexible 3,3,4,4-benzophenonetetracarboxylic acid dianhydride-4,4'-diaminodiphenyl ether (BTDA-ODA) PI with ZnO nanoparticles (3-4 nm). Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) depict that the ZnO nanoparticles function as a physical cross-linking agent with PI through hydrogen bonding between the OH on the ZnO nanoparticles and the C=O of the imide groups. ZnO nanoparticles in the rigid PMDA-ODA matrix cause a larger percentage decrease in the coefficient of linear thermal expansion (CTE) than in the flexible BTDA-ODA matrix. The BTDA-ODA/ZnO hybrid films have two transition peaks in dynamic mechanical tan curves, but PMDA-ODA/ZnO hybrid films only have one transition peak. Thermogravimetric analysis reveals that ZnO decreases the thermal degradation temperature (T-d) in both hybrid films, but less so in PMDA-ODA/ZnO films. Trans-mission electron microscopy (TEM) images reveal that the rigid matrix induces larger particle size (30-40 nm) compared to the flexible matrix (10-15 nm).
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    Simultaneous preparation of PI/POSS semi-IPN nanocomposites
    (2006-03-24)
    Chen, WY
    ;
    Ko, SH
    ;
    Hsieh, TH
    ;
    Chang, FC
    ;
    Wang, YZ
    This investigation presents a simultaneous and convenient approach to produce a high-performance polyimide with a low dielectric constant by introducing the octa-acrylated polyhedral oligomeric silsesquioxane (methacrylated-POSS) into a polyimide matrix to form polyimide semi-interpenetrating polymer network (semi-IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) results indicate that the self-curing of methacrylated-POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi-IPN structure of polyimide[POSS-PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50-60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly crosslinked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer-scale porous structure of POSS.
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    Synthesis and characterization of polyimide-silica nanocomposites using novel fluorine-modified silica nanoparticles
    (2007-04-15)
    Mo, Te-Cheng
    ;
    Wang, Hong-Wen
    ;
    Chen, San-Yan
    ;
    Dong, Rui-Xuan
    ;
    Kuo, Chien-Hung
    Polyimide-silica nanocomposites were synthesized with 4,4'-oxydianiline, 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride), and fluorine-modified silica nanoparticles. Fluorinated precursors such as 4",4'"-(hexafluoroisopropylidene)bis(4-phenoxyaniline) (6FBPA) and 4,4'-(hexafluoroisopropylindene)diphenol (BISAF) were employed to modify the surface of the silica nanoparticles. The microstructures and thermal, mechanical, and dielectric properties of the polymide-silica nanocomposites were investigated. An improvement in the thermal stability and storage modulus of the polyimide nanocomposites due to the addition of the modified silica nanoparticles was observed. The microstructures of the polyimide-silica nanocomposites containing 6FBPA-modified silica exhibited more uniformity than those of the nanocomposites containing BISAF-modified silica. The dielectric constants of the polyimide were considerably reduced by the incorporation of pristine silica or 6FBPA-modified silica but not BISAF-modified silica. The addition of a modifier with higher fluorine contents did not ensure a lower dielectric constant. The uniformity of the silica distribution, manipulated by the reactivity of the modifier, played an important role in the reduction of the dielectric constant. Using 6FBPA-modified silica nanoparticles demonstrated an effective way of synthesizing low-dielectric-constant polyimide-silica nanocomposites. (c) 2007 Wiley Periodicals, Inc.
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    Electroluminescence and electron transport characteristics of aromatic polyimides containing 1,3,4-oxadiazole moiety
    (2007-06-13)
    Hsu, Shou-Chian
    ;
    Whang, Wha-Tzong
    ;
    Chao, Ching-Shiun
    ;
    材料科學與工程學系
    ;
    Department of Materials Science and Engineering
    Single and double layer polymer light-emitting diodes (LEDs) were fabricated by using 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based aromatic polyimides (APIs). All the resultant APIs have high glass transition temperatures (T-g>250 degrees C) and high thermal decomposition temperatures (T-d>510 degrees C). The APIs exhibit broad fluorescent characteristic, and the fluorescent intensity is related to the intermolecular chain's orientation. BAO-3,3 '-oxydiphthalic anhydride (ODPA) and BAO-4,4 '-(hexafluoro-iso-propylidene) diphthalic anhydride show electroluminescent property in single layer LED devices. By inserting BAO-ODPA in the poly(p-phenylene vinylene)-poly(vinylalcohol) LED device to form a double layer device, the EL efficiency can be improved by two orders of magnitude. (C) 2007 Elsevier B.V. All rights reserved.
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    A simple approach toward low-dielectric polyimide nanocomposites: Blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane
    (2008-09-15)
    Ye, Yun-Sheng
    ;
    Yen, Ying-Chieh
    ;
    Chen, Wen-Yi
    ;
    Cheng, Chih-Chia
    ;
    Chang, Feng-Chih
    This article describes a new and simple method for preparing polyimide nanocomposites that have very low dielectric constants and good thermal properties: simply through blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane derivative, octakis(dimethylsiloxyhexafluoropropyl) silsesquioxane (OF). The low polarizability of OF is compatible with polyimide matrices, such that it can improve the dispersion and free volume of the resulting composites. Together, the higher free volume and lower polarizability of OF are responsible for the lower dielectric constants of the PI-OF nanocomposites. This simple method for enhancing the properties of polyimides might have potential applicability in the electronics industry. (C) 2008 Wiley Periodicals, Inc.