Distribution by Scientific Domains

Kinds of Dianhydride

  • aromatic dianhydride
  • benzophenone tetracarboxylic dianhydride
  • benzophenonetetracarboxylic dianhydride
  • biphenyltetracarboxylic dianhydride
  • pyromellitic dianhydride
  • tetracarboxylic dianhydride
  • various aromatic dianhydride

  • Selected Abstracts

    Gas-Phase Electron-Diffraction Investigation and Quantum-Chemical Calculations of the Structure of 1,5-Dimethylsemibullvalene-2,4,6,8-tetracarboxylic Dianhydride

    Svein Samdal
    The bridged homotropilidines have been of interest for decades because their molecules offer the potential for homoaromaticity. Although many of these have been shown not to be homoaromatic, the energy differences of the delocalized (homoaromatic) forms and the localized (nonhomoaromatic) ones, and the barriers to the interconversion of the localized forms via a Cope rearrangement, have been found to vary greatly. The title compound is a strong candidate for homoaromaticity, and, since the structures of the possible localized and delocalized forms could differ significantly, we have carried out an electron-diffraction investigation of it augmented by quantum-mechanical calculations with different basis sets at several levels of theory. Three models were explored: one representing a localized form of Cs symmetry, one a delocalized form of C2v symmetry, and one a 2,:,1 mixture of the localized/delocalized forms. Although none of the models could be ruled out, the experimental evidence slightly favors the Cs form. These results are consistent with those from the DFT B3PW91 calculations with basis sets ranging from 6-31G(d) to cc-pVTZ, which, surprisingly, predict essentially equal thermally corrected free energies for each. The results are discussed. [source]

    ,-(Hydroxyalkyl)naphthalene-tetracarboxdiimides: Organic White Pigments,

    Heinz Langhals
    Abstract Naphthalene-1,8:4,5-tetracarboxdiimides were prepared from cyanoacetic acid and its alkylation, reduction and condensation with naphthalenetetracarboxylic dianhydride and exhibit strong light-scattering and opacifying properties. Applications are discussed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Porous Polymersomes with Encapsulated Gd-Labeled Dendrimers as Highly Efficient MRI Contrast Agents

    Zhiliang Cheng
    Abstract The use of nanovesicles with encapsulated Gd as magnetic resonance (MR) contrast agents has largely been ignored due to the detrimental effects of the slow water exchange rate through the vesicle bilayer on the relaxivity of encapsulated Gd. Here, the facile synthesis of a composite MR contrast platform is described; it consists of dendrimer conjugates encapsulated in porous polymersomes. These nanoparticles exhibit improved permeability to water flux and a large capacity to store chelated Gd within the aqueous lumen, resulting in enhanced longitudinal relaxivity. The porous polymersomes, ,130,nm in diameter, are produced through the aqueous assembly of the polymers, polyethylene oxide- b -polybutadiene (PBdEO), and polyethylene oxide- b -polycaprolactone (PEOCL). Subsequent hydrolysis of the caprolactone (CL) block resulted in a highly permeable outer membrane. To prevent the leakage of small Gd-chelate through the pores, Gd was conjugated to polyamidoamine (PAMAM) dendrimers via diethylenetriaminepentaacetic acid dianhydride (DTPA dianhydride) prior to encapsulation. As a result of the slower rotational correlation time of Gd-labeled dendrimers, the porous outer membrane of the nanovesicle, and the high Gd payload, these functional nanoparticles are found to exhibit a relaxivity (R1) of 292 109,mM,1,s,1 per particle. The polymersomes are also found to exhibit unique pharmacokinetics with a circulation half-life of >3.5,h and predominantly renal clearance. [source]

    n-Type Doping of Organic Thin Films Using Cationic Dyes,

    A. Werner
    Abstract We present an approach to stable n-type doping of organic matrices using organic dopants. In order to circumvent stability limitations inherent to strong organic donors, we produce the donor from a stable precursor compound in situ. As an example, the cationic dye pyronin B chloride is studied as a dopant in a 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) matrix. Conductivities of up to 1.9,,10,4,S,cm,1 are obtained for doped NTCDA, two orders of magnitude higher than the conductivity of NTCDA doped with bis(ethylenedithio)-tetrathiafulvalene as investigated previously, and four orders of magnitude higher than nominally undoped NTCDA films. Field-effect measurements are used to prove n-type conduction and to study the doping effect further. The findings are interpreted using a model of transport in disordered solids using a recently published model. Combined FTIR, UV-vis, and mass spectroscopy investigations suggest the formation of leuco pyronin B during sublimation of pyronin B chloride. [source]

    Synthesis and characterization of novel polyimide/SiO2 nanocomposite materials containing phenylphosphine oxide via sol-gel technique

    Canan Kizilkaya
    Abstract In this article, a series of novel polyimide/silica (PI/SiO2) nanocomposite coating materials were prepared from tetraethoxysilane (TEOS), ,-glycidyloxypropyltrimethoxysilane (GOTMS), and polyamic acid (PAA) via sol-gel technique. PAA was prepared by the reaction of 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA) and bis (3-aminophenyl) phenyphosphine oxide (BAPPO) in N -methyl-2- pyrrolidone (NMP). BAPPO was synthesized hydrogenation of bis (3-nitrophenyl) phenyphosphine oxide (BNPPO) in the presence of Pd/C. The silica content in the hybrid coating materials was varied from 0 to 20 wt %. The molecular structures of the composite materials were analyzed by means of FT-IR and 29Si-NMR spectroscopy techniques. The physical and mechanical properties of the nanocomposites were evaluated by various techniques such as, hardness, contact angle, and optical transmission and tensile tests. These measurements revealed that all the properties of the nanocomposite coatings were improved noticeable, by the addition of sol-gel precursor into the coating formulation. Thermogravimetric analysis showed that the incorporation of sol-gel precursor into the polyimide matrix leads to an enhancement in the thermal stability and also flame resistance properties of the coating material. The surface morphology of the hybrid coating was characterized by scanning electron microscopy (SEM). SEM studies indicated that nanometer-scaled inorganic particles were homogenously dispersed throughout the polyimide matrix 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Synthesis of a new photoreactive gelatin with BTDA and HEMA derivatives

    Fan-Chun Ding
    Abstract A novel bio-affinitive, photocuring, and membrane-forming gelatin derivative was synthesized in this study. This process was based on the amide formation between carboxylic acid and the amine in methanol,water media using dicyclohexyl-carbodiimide (DCC) as a condenser. Gelatin and glycine were the sources of amine in the model reaction. Since there were two anhydride groups in each 3,3,,4,4,-benzophenone tetra-carboxylic dianhydride (BTDA) molecule, two 2-hydroxyethyl methacrylate (HEMA) molecules were used to induce the ring-opening reaction of BTDA and release two carboxylic acid groups. The resulting photoreactive gelatin was called GE-BTHE, of which the photoreactive component was the ketone groups of BTDA and HEMA that played the role of double bond supplier. This photoreactive gelatin could be converted from the transparent liquid phase into swollen membrane by a 6-min irradiation of high pressure mercury lamp. The most efficient irradiation was at 267 nm and the highest degree of swelling of the cured GE-BTHE membrane could reach 5.9. The elongation from the dried gel remained 5,10%, i.e., relatively elastic. The properties of this gelatin derivative were investigated using amide formation analysis, calculation of the gel content and the swelling ratio, and monitoring of the photocuring process. The GE-BTHE synthesized in this study should be very potential in applications such as protective wound dressings and hemostatic absorbents for minimally invasive surgery. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Relationship between gas transport properties and fractional free volume determined from dielectric constant in polyimide films containing the hexafluoroisopropylidene group

    Sou Miyata
    Abstract The dielectric constant and gas transport properties (i.e., permeability, diffusivity, and solubility) in 2,2,-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)-based polyimides were systematically investigated in terms of their polymer fractional free volumes (FFVs) at 30C. The permeability and diffusion coefficients of the 6FDA-based polyimide films to hydrogen, oxygen, nitrogen, methane, and carbon dioxide were correlated with their FFVs estimated using van Krevelen's group contribution method. There appeared, however, small linear correlation coefficients. Linear correlations were also observed between the gas transport properties and dielectric constant of these polyimides. This study described FFVas a function of the dielectric constant based on the Clausius-Mossotti equation. It was found that the gas permeability and diffusion coefficients of these 6FDA-based polyimide films increased as their dielectric constant-based FFV increased. A better linear relationship was observed between the gas transport properties and the FFV determined from the polymer dielectric constant in comparison to that estimated using the group contribution method. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

    Preparation of poly(amic acid) and polyimide derived from 3,3,,4,4,-benzophenonetetracarboxylic dianhydride with different diamines by microwave irradiation

    Quantao Li
    Abstract Polycondensation-type poly(amic acid) (PAA) was synthesized with 3,3,,4,4,-benzophenonetetracarboxylic dianhydride as a dianhydride monomer and 4,4,-diaminodiphenylmethane and 4,4,-oxydianiline as diamine monomers under microwave irradiation in dimethylformamide. Then, PAA was used to make polyimide (PI) by imidization at a low temperature. The structure and performance of the polymers were characterized with Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR), viscosity, X-ray diffraction (XRD), and thermogravimetry (TG) curve analyses. The FTIR spectra of the polymers showed characteristic peaks of PI around 1779 and 1717 cm,1. The 1H-NMR spectrum of PAA indicated a singlet at 6.55 ppm assigned to NHCO and a singlet at 10.27 ppm assigned to carboxylic acid protons. The XRD spectrum demonstrated that the obtained PI had a low-order aggregation structure with a d -spacing of 0.5453 nm. The TG results revealed that the PI was thermally stable with 10% weight loss at 565C in an N2 atmosphere. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

    Copoly(peryleneimide)s containing 1,3,4-oxadiazole rings: Synthesis and properties

    Radu-Dan Rusu
    Abstract New copolyimides containing perylenediimide, oxadiazole and hexafluoroisopropylidene moieties were prepared by one-step polycondensation reaction in solution at high temperature of aromatic diamines containing preformed oxadiazole ring with a mixture of a dianhydride having a perylene ring and another dianhydride with hexafluoroisopropylidene unit. The thermal stability and glass transition temperatures of these copolyimides were measured and compared with those of related polyimides. The solid polymers were also studied by polarized light microscopy and X-ray diffraction which revealed a semicrystalline state consisting of face-to-face arranged columns of perylenediimide units. The film-forming ability and properties of the resulting thin films were investigated by using atom force microscopy and scanning electron microscopy which showed that the films were organized into self-assembled rod-like structures. The UV-Vis and photoluminescence properties in solution and in solid state were also investigated. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4230,4242, 2010 [source]

    Benzoxazine containing polyester thermosets with improved adhesion and flexibility

    Alev Tuzun
    Abstract High molecular weight polyesters containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diol functional monomer is synthesized through the Mannich and subsequent ring closure reactions of bisphenol-A, paraformaldehyde, and 5-amino-1-pentanol. Polycondensation of the resulting benzoxazine and pyromellitic dianhydride or 4-4,-(hexafluoroisopropylidene) diphatalic anhydride with or without dibutyltin laurate yielded the corresponding polyesters with the molecular weights between 5800 and 7000 Da. The structures of the precursor diol monomer and the resulting polyesters are confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy analysis. Curing behavior of both the monomer and polymers has also been studied by differential scanning calorimetry. Flexible films of the polyesters were obtained by solvent casting on tin plates and crosslinked by heating in the absence of any catalyst. The cured films exhibited high flexibility and adhesion on the tin plates as determined by ASTM and DIN tests. Thermal properties of the cured polymers were also investigated by thermogravimetric analysis (TGA). 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4279,4284, 2010 [source]

    Poly(vinyltriethoxysilane) modified MWCNT/polyimide nanocomposites,Preparation, morphological, mechanical, and electrical properties

    Siu-Ming Yuen
    Abstract Multi-walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES-MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4,-oxydianiline with 3,3,,4,4,-benzophenone tetracarboxylic dianhydride. PVTES-MWCNT were then mixed with polyamic acid and heated to 300 C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (SiOSi). The PVTES-MWCNT was analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. The PVTES-MWCNT/polyimide composites were analyzed by CP/MAS solid state 29Si nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES-MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES-MWCNT. 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 803,816, 2008 [source]

    Synthesis and properties of poly(amic acid)s and polyimides based on 2,2,,6,6,-biphenyltetracarboxylic dianhydride

    Katsuya Sakayori
    Abstract Poly(amic acid)s (PAAs) having the high solution stability and transmittance at 365 nm for photosensitive polyimides have been developed. PAAs with a twisted conformation in the main chains were prepared from 2,2,,6,6,-biphenyltetracarboxylic dianhydride (2,2,,6,6,-BPDA) and aromatic diamines. Imidization of PAAs was achieved by chemical treatment using trifluoroacetic anhydride. Among them, the PAA derived from 2,2,,6,6,-BPDA and 4,4,-(1,3-phenylenedioxy)dianiline was converted to the polyimide by thermal treatment. The heating at 300 C under nitrogen did not complete thermal imidization of PAAs having glass-transition temperatures (Tg)s higher than 300 C to the corresponding PIs. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6385,6393, 2006 [source]

    Synthesis and properties of polyimides bearing acid groups on long pendant aliphatic chains

    Tomohiro Yasuda
    Abstract A series of novel polyimide electrolytes having long pendant sulfo- or phosphoalkoxy groups were synthesized for fuel-cell applications. Sulfodecyloxy-, phosphodecyloxy-, and sulfophenoxydodecyloxy-substituted benzidine monomers were synthesized from dihydroxybenzidine. These monomers were copolymerized with naphthalene tetracarboxylic dianhydride and fluorenylidene dianiline to give the corresponding polyimides. A flexible, ductile, and self-standing membrane was obtained via casting from the polyimide solution. Because the acid groups were on long pendant side chains and away from the main chains, the polyimide membrane showed improved oxidative and hydrolytic stability in comparison with the polyimides with sulfonic acid groups on the main chains or on the short side chains. High thermal stability (no glass-transition temperature and a decomposition temperature > 200 C) was also obtained. The polyimide membrane displayed high proton conductivity of 10,1 S cm,1 at 120 C. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3995,4005, 2006 [source]

    Novel organosoluble and colorless poly(ether imide)s based on 3,3-bis[4-(3,4-dicarboxyphenoxy)phenyl]phthalide dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

    Chin-Ping Yang
    Abstract A novel series of colorless and highly organosoluble poly(ether imide)s were prepared from 3,3-bis[4-(3,4-dicarboxyphenoxy)phenyl]phthalide dianhydride with various fluorinated aromatic bis(ether amine)s via a conventional two-stage process that included ring-opening polyaddition to form the poly(amic acid)s followed by cyclodehydration to produce the polymer films. The poly(ether imide)s showed excellent solubility, with most of them dissoluble at a concentration of 10 wt % in amide polar solvents, in ether-type solvents, and even in chlorinated solvents. Their films had a cutoff wavelength between 358 and 373 nm, and the yellowness index ranged from 3.1 to 9.5. The glass-transition temperatures of the poly(ether imide) series were recorded between 237 and 297 C, the decomposition temperatures at 10% weight loss were all above 494 C, and the residue was more than 54% at 800 C in nitrogen. These films showed high tensile strength and also were characterized by higher solubility, lighter color, and lower dielectric constants and moisture absorption than an analogous nonfluorinated polyimide series. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3140,3152, 2006 [source]

    Synthesis and characterization of proton-conducting copolyimides bearing pendant sulfonic acid groups

    Yan Yin
    Abstract A series of sulfonated copolyimides (co-SPIs) bearing pendant sulfonic acid groups were synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), bis(3-sulfopropoxy) benzidines (BSPBs), and common nonsulfonated diamines via statistical or sequenced polycondensation reactions. Membranes were prepared by casting their m -cresol solutions. The co-SPI membrane had a microphase-separated structure composed of hydrophilic and hydrophobic domains, but the connecting behavior of hydrophilic domains was different from that of the homo-SPIs. The co-SPI membranes displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. With water uptake values of 39,94 wt %, they showed dimensional changes in membrane thickness of about 0.11,0.58, which were much lower than those of homo-SPIs. The proton conductivity , values of co-SPI membranes with ion exchange capacity values ranging from 1.95,2.32 meq/g increased sigmoidally with increasing relative humidity. They displayed , values of 0.05,0.16 S/cm at 50 C in liquid water. Increasing temperature up to 120 C resulted in further increase in proton conductivity. The co-SPI membranes showed relatively good conductivity stability during the aging treatment in water at 100 C for 300 h. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1545,1553, 2005 [source]

    Structure,property correlations of sulfonated polyimides.


    Abstract A series of six-membered sulfonated polyimides were synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4,-diaminobiphenyl 2,2,-disulfonic acid as the sulfonated diamine, and various nonsulfonated diamine monomers having different bridging groups. These bulky bridging groups have the capacity to increase hydrolytic stability and proton conductivity. Polyimides with bulky bridging groups showed increased solubility but exhibited lower thermal stability. The ion exchange capacity and water uptake reduced with increase in the bulkiness of the bridging group. This was attributed to the increase in the molecular weight of the repeating unit and hence effectively reduced the sulfonic acid content. In low temperatures, the conductivity was lower than Nafion115 and, with increase in temperature, the conductivity rapidly increased and exhibited better conductivity than Nafion115. Polyimides with bulky bridging groups 4-amino phenyl sulfone, and 2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane showed higher conductivity than other polyimides and Nafion115 despite low ion exchange capacity. The hydrolytic stability of the polyimides with bulky bridging groups was higher than the polyimides with less bulky atoms because of the imparted flexibility. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3612,3620, 2004 [source]

    Synthesis and properties of novel polyimides derived from 2,2,,3,3,-benzophenonetetracarboxylic dianhydride

    Xing-Zhong Fang
    Abstract A new synthetic route to 2,2,,3,3,-BTDA (where BTDA is benzophenonetetracarboxylic dianhydride), an isomer of 2,3,,3,,4,-BTDA and 3,3,,4,4,-BTDA, is described. Single-crystal X-ray diffraction analysis of 2,2,,3,3,-BTDA has shown that this dianhydride has a bent and noncoplanar structure. The polymerizations of 2,2,,3,3,-BTDA with 4,4,-oxydianiline (ODA) and 4,4,-bis(4-aminophenoxy)benzene (TPEQ) have been investigated with a conventional two-step process. A trend of cyclic oligomers forming in the reaction of 2,2,,3,3,-BTDA and ODA has been found and characterized with IR, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and elemental analyses. Films based on 2,2,,3,3,-BTDA/TPEQ can only be obtained from corresponding polyimide (PI) solutions prepared by chemical imidization because those from their polyamic acids by thermal imidization are brittle. PIs from 2,2,,3,3,-BTDA have lower inherent viscosities and worse thermal and mechanical properties than the corresponding 2,3,,3,,4,-BTDA- and 3,3,,4,4,-BTDA-based PIs. PIs from 2,2,,3,3,-BTDA and 2,3,,3,,4,-BTDA are amorphous, whereas those from 3,3,,4,4,-BTDA have some crystallinity, according to wide-angle X-ray diffraction. Furthermore, PIs from 2,2,,3,3,-BTDA have better solubility, higher glass-transition temperatures, and higher melt viscosity than those from 2,3,,3,,4,-BTDA and 3,3,,4,4,-BTDA. Model compounds have been prepared to explain the order of the glass-transition temperatures found in the isomeric PI series. The isomer effects on the PI properties are discussed. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2130,2144, 2004 [source]

    Sulfonated naphthalene dianhydride based polyimide copolymers for proton-exchange-membrane fuel cells.


    Abstract A novel sulfonated diamine, 3,3,-disulfonic acid-bis[4-(3-aminophenoxy)phenyl]sulfone (SA-DADPS), was prepared from m -aminophenol and disodium-3,3,-disulfonate-4,4,-dichlorodiphenylsulfone. The conditions necessary to synthesize and purify SA-DADPS in high yields were investigated in some detail. This disulfonated aromatic diamine, containing ether and sulfone linkages, was used to prepare N -methyl-2-pyrrolidinone-soluble, six-membered ring polyimide copolymers containing pendent sulfonic acid groups by a catalyzed one-step high-temperature polycondensation in m -cresol. These materials showed much improved hydrolytic stability with respect to phthalimides. High-molecular-weight film-forming statistical copolymers with controlled degrees of disulfonation were prepared through variations in the stoichiometric ratio of disulfonated diamine (SA-DADPS) in its soluble triethylamine salt form to several unsulfonated diamines. Three unsulfonated diamines, bis[4-(3-aminophenoxy)phenyl] sulfone, 4,4,-oxydianiline, and 1,3-phenylenediamine, were used to prepare the copolymers. The characterization of the copolymers by 1H NMR, Fourier transform infrared, ion-exchange capacity, and thermogravimetric analysis demonstrated that SA-DADPS was quantitatively incorporated into the copolymers. Solution-cast films of the sulfonated copolymers were prepared and afforded tough, ductile membranes with high glass-transition temperatures. Methods were developed to acidify the triethylammonium salt membranes into their disulfonic acid form, this being necessary for proton conduction in a fuel cell. The synthesis and characterization of these materials are described in this article. Future articles will describe the performance of these copolymers as proton-exchange membranes in hydrogen/air and direct methanol fuel cells. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 862,874, 2004 [source]

    Synthesis of autophotosensitive hyperbranched polyimides based on 3,3,,4,4,-benzophenonetetracarboxylic dianhydride and 1,3,5-tris(4-aminophenoxy)benzene via end capping of the terminal anhydride groups by ortho -alkyl aniline

    Huan Chen
    Abstract Benzophenone-containing, anhydride-terminated hyperbranched poly(amic acid)s were end-capped by ortho -alkyl aniline in situ and then chemically imidized, yielding autophotosensitive hyperbranched polyimides. The polyimides were soluble in strong polar solvents, such as N -methyl-2-pyrrolidone, N -dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis revealed their excellent thermal stability, with a 5 wt % thermal loss temperature in the range of 527,548 C and a10 wt % thermal loss temperature in the range of 562,583 C. The strong absorption of the polyimide films in ultraviolet,visible spectra at 365 nm indicated that the hyperbranched polyimides were patternable. Highly resolved images with a line width of 6 ,m were developed by ultraviolet exposure of the polymer films. A well-defined image with lines as thin as 3 ,m was also patterned, but the lines were rounded at the edges. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2026,2035, 2003 [source]

    Novel side-chain liquid-crystalline polyimide for film materials

    Haojun Fan
    Abstract A novel side-chain liquid-crystalline polyimide (SLCPI) was prepared via copolycondensation from 3,5-diamino-benzonic-4,-biphenyl ester, 4,4,-diamino- biphenyl ether, and 3,3,,4,4,-oxydiphthalic dianhydride. The energy-minimized structure and liquid crystallinity of SLCPI were investigated by molecular modeling, differential scanning calorimetry (DSC), wide-angle X-ray scattering, and polarized optical microscopy, respectively. The results indicated that this polyimide (PI) with side-chain mesogenic units exhibited a nematic NI phase. Because of the in situ self-reinforcement of side-chain mesogenic units, the improved tensile strength and modulus of PI films reached 270% and 300%, respectively. The coefficient of thermal expansion of films decreased by 40%. DSC and thermogravimetric analyses indicated that the phase-transition temperature of SLCPI was above 240 C, and the 5% weight-loss temperature was above 520 C. Moreover, copolycondensation of two diamines with dianhydride and incorporation of pendent mesogenic units diminished the regularity and symmetry of main chains; as a result, SLCPI exhibits good film processability. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 554,559, 2003 [source]

    Synthesis of nonlinear optical polyimides containing azodiamine derivative chromophores and their electrooptic and thermal properties

    Yuming Zhou
    Abstract Some thermally stable second-order nonlinear optical (NLO) polyimides were synthesized. The polyimides were prepared by the ring-opening polyaddition of 4,4,-(hexafluoroisopropylidene) diphthalic anhydride and pyromellitic dianhydride with two aromatic azodiamine derivatives as the NLO chromophores. These chromophores, based on a nitro group connected with azobenzene as the acceptor end of a donor,,-bridge,acceptor chromophore and a diamine group as the donor end, had specific chemical stability. On the basis of ZERNER'S INDO methods, according to the sum-over-states formula, a program for the calculation of nonlinear second-order optical susceptibilities was devised. The resulting polyimides had high number-average and weight-average molecular weights of up to 26,000 and 53,500, respectively, and a large glass-transition temperature of 248 C. With an in situ poling and temperature ramping technique, the optimal temperatures (Topt's) for corona poling were obtained for the largest second-order NLO response. The electrooptic coefficient (,33) of a polyimide at a wavelength of 830 nm was up to 21 pm/V after corona poling under its Topt, and the value remained at elevated temperatures (>90.6% was retained at 240 C for >120 h). The thermal stability of the NLO polyimides was studied with UV spectrometry after poling of the films. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2478,2486, 2002 [source]

    Poly(ethylene terephthalate) reinforced by N,N,-diphenyl biphenyl-3,3,,4,4,-tetracarboxydiimide moieties

    Jun Xiao
    Abstract Starting with 3,3,,4,4,-biphenyltetracarboxylic dianhydride and methyl aminobenzoate, we synthesized a novel rodlike imide-containing monomer, N,N,-bis[p -(methoxy carbonyl) phenyl]-biphenyl-3,3,,4,4,-tetracarboxydiimide (BMBI). The polycondensation of BMBI with dimethyl terephthalate and ethylene glycol yielded a series of copoly(ester imide)s based on the BMBI-modified poly(ethylene terephthalate) (PET) backbone. Compared with PET, these BMBI-modified polyesters had higher glass-transition temperatures and higher stiffness and strength. In particular, the poly(ethylene terephthalate imide) PETI-5, which contained 5 mol % of the imide moieties, had a glass-transition temperature of 89.9 C (11 C higher than the glass-transition temperature of PET), a tensile modulus of 869.4 MPa (20.2 % higher than that of PET), and a tensile strength of 80.8 MPa (38.8 % higher than that of PET). Therefore, a significant reinforcing effect was observed in these imide-modified polyesters, and a new approach to higher property polyesters was suggested. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 852,863, 2002; DOI 10.1002/pola.10169 [source]

    Organosoluble and transparent polyimides derived from alicyclic dianhydride and aromatic diamines

    J. G. Liu
    Abstract Organosoluble polyimides were synthesized with the alicyclic dianhydride 1,8-dimethylbicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and aromatic diamines. The polyimides possessed good solubility both in strong dipolar solvents and in common solvents; the thermal decomposition temperature of the polyimides exceeded 420 C. Strong and flexible films of the polyimides, with the cutoff of ultraviolet,visible absorption lower than 310,320 nm, exhibited good features as the alignment layers for nematic liquid crystals with pretilt angles of 1.5,2.9. 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 110,119, 2002 [source]

    Synthesis and characterization of novel polyimide from bis-(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxide

    Kwang Un Jeong
    Abstract A novel diamine, bis-(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), containing phosphine oxide and fluorine moieties was prepared via the Grignard reaction from an intermediate, 4-(trifluoromethyl)phenyl diphenyl phosphine oxide, that was synthesized from diphenylphosphinic chloride and 4-(trifluoromethyl)bromobenzene, followed by nitration and reduction. The monomer was characterized by Fourier transform infrared (FTIR), 1H NMR, 31P NMR, 19F NMR spectroscopies; elemental analysis; melting point measurements; and titration and was used to prepare polyimides with a number of dianhydrides such as pyromellitic dianhydride (PMDA), 5,5,-[2,2,2-trifluoro-1-(trifluoromethyl)ethyliden]-bis-1,3-isobenzofuranedione (6FDA), 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4,-oxydiphthalic dianhydride (ODPA). Polyimides were synthesized via a conventional two-step route; preparation of polyamic acids, followed by solution imidization, and the molecular weight were controlled to 20,000 g/mol. Resulting polyimides were characterized by FTIR, NMR, DSC, and intrinsic viscosity measurements. Refractive-index, dielectric constant, and adhesive properties were also determined. The properties of polyimides were compared with those of polyimides prepared from 1,1-bis-(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3FDAm) and bis-(3-aminophenyl) phenyl phosphine oxide (mDAPPO). The polyimides prepared from mDA3FPPO provided high glass-transition temperatures (248,311 C), good thermal stability, excellent solubility, low birefringence (0.0030,0.0036), low dielectric constants (2.9,3.1), and excellent adhesive properties with Cu foils (107 g/mm). 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3335,3347, 2001 [source]

    Synthesis and Properties of 6FDA-MDA Copolyimide Membranes: Effects of Diamines and Dianhydrides on Gas Separation and Pervaporation Properties

    Shude Xiao
    Abstract 6FDA-MDA-based polyimides were synthesized from a one-step polycondensation of 6FDA and MDA with other diamines and dianhydrides. The polyimides were characterized by GPC, FT-IR and NMR, and dense membranes were prepared from their solutions for gas separation and pervaporation. Gas separation and pervaporation properties were investigated using the linear moiety contribution method. The moiety contribution factors were used to analyze the effects of the dianhydride and diamine monomers on gas permselectivity and pervaporation permeation flux. It was shown that the steric effects and flexibility of the monomers and the interactions between the membrane and the penetrants accounted for the differences in separation properties. [source]

    In situ Preparation of Polyimide Composites Based on Functionalized Carbon Nanotubes

    Rohit Srivastava
    Abstract Three series of composite films based on polyimide and MWNTs were prepared by conversion of pyromellitic dianhydride and 4,4,-oxydianiline in the presence of the nanotubes, followed by thermal imidization. Carboxy- and amino-functionalized as well as unmodified nanotubes were used. It was demonstrated that just 0.5 wt.-% of nanotubes increased the tensile properties of the composite films distinctly. Surprisingly, a significant influence of the functional groups on the mechanical performance of the composite films could not be demonstrated. However, it was shown that functional groups may reduce the conductivity of the films. Furthermore, the influence of ultrasonication is discussed. [source]

    New organosoluble polyimides with low dielectric constants derived from bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl] diphenylmethylene

    Der-Jang Liaw
    Abstract A new kink diamine with trifluoromethyl group on either side, bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]diphenylmethane(BTFAPDM), was reacted with various aromatic dianhydrides to prepare polyimides via poly (amic acid) precursors followed by thermal or chemical imidization. Polyimides were prepared using 3,3,, 4,4,-biphenyltetracarboxylic dianhydride(1), 4,4,-oxydiphthalic anhydride(2), 3,3,,4,4,-benzophenonetetracarboxylic dianhydride (3), 4,4,-sulfonyldiphthalic anhydride(4), and 4,4,-hexafluoroisopropylidene-diphathalic anhydride(5). The fluoro-polyimides exhibited low dielectric constants between 2.46 and 2.98, light color, and excellent high solubility. They exhibited glass transition temperatures between 227 and 253C, and possessed a coefficient of thermal expansion (CTE) of 60-88 ppm/C. Polymers PI-2, PI-3, PI-4, PI-5 showed excellent solubility in the organic solvents: N -methyl-2-pyrrolidinone (NMP), N,N -dimethylacetamide (DMAc), N,N -dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridkie and tetrahydrofuran (THF). Inherent viscosity of the polyimides were found to range between 0.58 and 0.72 dLg-1. Thermogravimetric analysis of the polyimides revealed a high thermal stability decomposition temperature in excess of 500C in nitrogen. Temperature at 10 % weight loss was found to be in the range 506-563C and 498-557C in nitrogen and air, respectively. The polyimide films had a tensile strength in the range 75-87 MPa; tensile modulus, 1.5-2.2 GPa; and elongation at break, 6-7%. [source]

    Polyimide nanocomposites: Comparison of their properties with precursor polymer nanocomposites

    Jin-Hae Chang
    A precursor poly(amic acid) was obtained by solution polymerization of pyromellitic dianhydride and benzidine in N, N-dimethylacetamide. Poly(amic acid)/Organoclay hybrids were prepared by the solution intercalation method with dodecylamine-montmorillonite. A polyimide hybrid was obtained from poly(amic acid) hybrid by heat treatment at various temperatures. The film type polyimide hybrids showed better thermal properties than poly(amic acid) hybrids. Also, the thermal stability of the two polymer hybrids were enhanced linearly with increasing clay content from 0 to 8 wt%. Tensile properties and gas barriers of the hybrids, however, were enhanced remarkably compared to pristine polymers. Intercalations of the polymer chains in clar were examined through wide angle X-ray diffraction (XRD) and electron microscopy (SEM and TEM). Transmission electron microscopy revealed that a partially exfoliated structure had been obtained from polyimide/organo-clay hybrids. [source]

    Heterocyclic polyimides containing siloxane groups in the main chain

    Mariana-Dana Damaceanu
    Abstract BACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings. RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole-diamines and a dianhydride containing a siloxane bridge (R2SiOSiR2). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 C and relatively low glass transition temperatures in the range 160,190 C. These polymers show strong photoluminescence in the blue spectral region. CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film-forming ability and that emit blue light, being attractive for applications in micro- and nanoelectronics and other related advanced fields. Copyright 2009 Society of Chemical Industry [source]

    Polycondensation of lactic acid catalyzed by organic acid anhydrides

    Yanbin Bai
    Abstract Poly(lactic acid) was prepared by the utilization of the acid anhydrides cis -butenedoic anhydride, phthalic anhydride and pyromellitic dianhydride as catalysts. The effect of the amount of catalyst, temperature and reaction time on the polymerization was investigated in detail. The results show that the acid anhydride catalysts are very efficient in bulk polycondensation, giving poly(D,L -lactic acid) with average molecular weights (Mw) of (1.7,2.3) 104 in high yield. Copyright 2007 Society of Chemical Industry [source]