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  • 1
    ISSN: 0887-624X
    Keywords: polyimide molecular composite ; crosslinking ; internal acetylene ; laminate processing ; high modulus ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyimide/polyimide molecular composite (MC) films comprised of a rigid polyimide derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) and a flexible polyimide derived from BPDA and bis (3,3'-diaminodiphenyl) acetylene (intA) and/or oxydianiline (ODA) were prepared by blending the polyamic acid solutions in 7 : 3 weight ratio, and then imidizing the blend films. Acetylene content in the flexible polyimide backbone was controlled by the ratio of intA and ODA. Cold-drawing of the blend polyamic acid films, followed by imidization, gives high modulus polyimide/polyimide MC films. The modulus of the MC films increased almost linearly with the draw ratio, reaching 25.5 GPa for the 40% drawn film. Acetylene groups in the flexible polyimide can be thermally cured to crosslink. The onset of exotherm appeared at 340°C on DSC, reaching maximum at 398°C. After the thermal crosslinking, the MC films maintained the high modulus, though elongation became small. Taking advantage of the crosslinkable acetylene units, two MC films were laminated and processed at 400°C for 20 min under 100 kg/cm2 to give a good-quality laminate film. The interface of the two films was strongly bonded through the crosslinking of acetylene groups. Laminate films maintained the high modulus afforded by the cold-drawing. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; Chiral stationary phase ; Cyclodextrin carbamate ; Hydrogen bonding interaction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following carbamate derivatives of cyclodextrins (CDs) were prepared as novel chiral stationary phases for capillary gas chromatography: hexakis(2,6-di-O-pentyl)-α-cyclodextrin hexa(3-n-propyl, 3-isopropyl, and 3-phenylcarbamate), heptakis-(2,6-di-O-pentyl)-β-cyclodextrin hepta(3-n-propyl, 3-isopropyl, and 3-phenylcarbamate), and octakis(2,6-di-O-pentyl)-γ-cyclodextrin octa(3-n-propyl, 3-isopropyl, and 3-isopropyl, and 3-phenylcarbamate). Metal capillary columns coated with these stationary phases resolved many kinds of racemic mixture. In general, they were especially effective towards polar compounds such as free alcohols, amines, and epoxides. The types of sample which were effectively resolved depended on the cavity size of the CD: α-CD derivatives were specifically effective toward compounds having linear alkyl chains, and β-CD derivatives toward compounds with phenyl groups. The results indicate that chiral separation with the cyclodextrin carbamates depends on the formation of inclusion complexes and also on the hydrogen-bonding interactions between the samples and the CD carbamates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0935-6304
    Keywords: GC ; Enantiomer separation ; Thermal stability ; Chiral stationary phase ; Metal capillary column ; Glass capillary column ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral stationary phase prepared by bonding L-valine-t-butylamide to XE-60 has been coated on glass and metal capillaries. The performances of the chiral glass and metal columns were equivalent to those of commercial fused silica capillary columns. The thermal stability of the glass column was examined up to 280°C. It was found that no appreciable change in separation factor (α value) was observed up to 230°C. The α values gradually decreased between 240 and 260°C, and enantiomer separation was no longer achieved at 280°C. It was concluded that the allowable upper limit temperature of the chiral stationary phase is between 230 and 240°C in the isothermal mode, and ca 260°C in temperature-programmed mode.
    Additional Material: 8 Ill.
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  • 4
    ISSN: 0887-624X
    Keywords: internal acetylene ; crosslinking ; soluble polyimide ; thermally curable ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0887-624X
    Keywords: internal acetylene ; crosslinking ; polyimide ; thermally curable ; high modulus ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,4′-Diaminodiphenylacetylene (p-intA) was reacted with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA) in N-methyl-2-pyrrolidone (NMP) to give poly(amic acid) solution of moderate to high viscosity. Thermal imidization gave polyimide having acetylene units that are linked para to the aromatic connecting unit. Polyimide having acetylene units that are linked meta to the aromatic connecting unit also was prepared utilizing 3,3′-diaminodiphenylacetylene (m-intA) for comparison. The crosslinking behavior of the acetylene units was observed with DSC. Exotherm due to the crosslinking of the para-linked acetylene units appeared at ca. 340 to 380°C depending on the structure of polyimide, whereas meta-linked acetylene units appeared at lower temperature as 340-350°C. After thermal treatment at high temperature such as 350 or 400°C, the amount of the exotherm became smaller and finally disappeared on DSC, confirming the progress of crosslinking. Dynamic mechanical properties of the polyimide films show that glass transition temperature increased with higher heat treatment, also confirming the progress of crosslinking. Tensile properties of the polyimide films showed that rigid polyimide films consisting of p-intA with BPDA or PMDA have considerably higher modulus than those consisting of m-intA. Cold-drawing of the poly(amic acid) followed by imidization gave much higher modulus in the case of rigid polyimide. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2395-2402, 1997
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: poly(urethane-imide) ; polyurethane ; polyimide ; poly(amide acid) ; oligo(amide acid) ; polyurethane prepolymer ; elastomer ; polymer network ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polymer blend consisting of polyimide (PI) and polyurethane (PU) was prepared by means of a novel approach. PU prepolymer was prepared by the reaction of polyester polyol and 2,4-tolylenediisocyanate (2,4-TDI) and then end-capped with phenol. Poly(amide acid) was prepared from pyromellitic dianhydride (PMDA) and oxydianiline (ODA). A series of oligo(amide acid)s were also prepared by controlling the molar ratio of PMDA and ODA. The PU prepolymer and poly(amide acid) or oligo(amide acid) solution were blended at room temperature in various weight ratios. The cast films were obtained from the blend solution and treated at various temperatures. With the increase of polyurethane component, the films changed from plastic to brittle and then to elastic. The poly(urethane-imide) elastomers showed excellent mechanical properties and moderate thermal stability. The elongation of films with elasticity was more than 300%. The elongation set after the breaking of films was small. From the dynamic mechanical analysis, all the samples showed a glass transition temperature (Tg) at ca. -15°C, corresponding to Tg of the urethane component, suggesting that phase separation occurred between the two polymer components, irrespective of polyimide content. TGA and DSC studies indicated that the thermal degradation of poly(urethane-imide) was in the temperature range 250-270°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3745-3753, 1997
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 19 (1986), S. 2093-2102 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyimides of various chemical structures were prepared from pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydianiline (ODA), and p-phenylenediamine (PDA). The cold-drawn polyimide films were prepared and carbonized. The electrical conductivity of the carbonized films enhanced linearly with the draw ratio. The effect of cold-drawing on the electrical conductivity is more remarkable with the rigid polyimides such as PMDA/PDA and BPDA/PDA than the flexible polyimides such as PMDA/ODA and BPDA/ODA. The tendency is well in accord with the effect of cold drawing on the improvement of modulus of polyimides. With the rigid polyimides, the higher alignment of polymer chain is supposed to be achieved by the cold-drawing. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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