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  • 1985-1989  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Electrical and interfacial properties of metal-polyimide-silicon structures (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2766-2771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and interfacial properties of gold-polyimide-silicon structures were studied experimentally by measuring the capacitance-voltage (C-V) characteristics. Two different polyimides of PMDA-ODA (synthesized from pyromellitic dianhydride and oxydianiline) and BTDA-ODA (from benzophenone tetracarboxylic dianhydride and oxydianiline), respectively, were employed. Polyimide coatings on n-type silicon (with a doping level N=5×1014 cm−3) were prepared by spin coating followed by thermal cure to range from 0.4 to 2.1 μm in thickness. The resulting high frequency C-V plots of these structures were well defined and could be described by the basic theory on metal-insulator-semiconductor (MIS) devices. Distinct differences in the C-V characteristics were observed, depending upon the polyimides. PMDA-ODA dielectrics resulted in C-V hysteresis, believed to be caused by charge injection. On the other hand, BTDA-ODA showed much smaller hysteresis, but some stretch-out in the C-V curve. These differences are attributed to the different interfacial properties of these polyimides in contact with silicon substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342767
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical conduction in polyimide films (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 318-326 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical conduction phenomena in polyimide (Kapton) films were studied with particular attention devoted to the separation of interface and bulk phenomena. The measurements were carried out with a variety of methods in the temperature range of 50 to 270 °C at electrical fields of 104 to 6×105 V/cm and at time intervals of up to 2×104 s after voltage application. Biased, two-side metallized samples yield, after sufficiently long voltage application, interface-controlled steady-state currents described by Schottky injection, modified by space-charge layers in the vicinity of the electrodes. The effective work function for aluminum-polyimide is estimated to be 1.7 eV in the temperature range between 100 and 270 °C. A distinct dependence of these currents on electrode material is observed. Bulk phenomena were studied on one-side metallized samples subject to positive-corona charge injection. At temperatures below 200 °C, significantly larger currents than those for biased, two-side metallized samples were observed. The current-voltage characteristics are ohmic at low fields and space-charge limited at high fields. From these data, trap modulated mobilities for positive carriers of 4×10−12 cm2/V s at 50 °C and 10−9 cm2/V s at 200 °C, ohmic bulk conductivities of 10−16 (Ω cm)−1 at 100 °C and 10−14 (Ω cm)−1 at 200 °C and an intrinsic carrier density of 5×1013 cm−3 independent of temperature are obtained. Activation energies for the mobility are between 0.2 and 0.8 eV for the temperature range between 50 and 200 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337646
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of a thermotropic, liquid-crystalline polyester comprising phenyl benzoate groups connected via a tris(ethylene oxide) spacer (1989)
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 3846-3850 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00200a005
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  • 4
    Electronic Resource
    Electronic Resource
    Corona poling and real-time second-harmonic generation study of a novel covalently functionalized amorphous nonlinear optical polymer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2559-2567 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films for optical second-harmonic generation (SHG) were prepared from a newly designed and synthesized amorphous polymer that incorporated a high density of active nonlinear optical groups (p-nitroaniline as attached side groups). For alignment of the nonlinear groups a very high electric field was applied by a corona discharge to the polymer films above Tg (125 °C). The subsequent freezing process resulted in a polymer film initially exhibiting a very high second-order nonlinear coefficient, d33=31 pm/V, measured by the Maker-fringe technique, plus excellent thermal, mechanical, and optical properties. The dynamics of polar alignment and decay, studied by in situ poling (or depoling) and SHG measurements, indicated a multiple exponential behavior with the average relaxation time somewhat longer than expected from extrapolation of the dielectric relaxations data according to the Williams–Landel–Ferry equation. The frozen-in SHG behavior at room temperature (∼100 °C below Tg) relaxed after 5 days to a stabilized value of 19 pm/V for d33.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344220
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  • 5
    Electronic Resource
    Electronic Resource
    Theory of nematic systems of semiflexible polymers. III. Phase equilibria in solutions (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 373-377 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Biphasic equilibria of lyotropic solutions of semiflexible polymers are calculated using the worm-like chain model with limiting curvature. The threshold concentration at incipient phase separation varies gradually with molecular weight to reach a finite value at infinite chain length. This limiting concentration is found to depend on the axial ratio of the persistence length and on the temperature. The theory is then applied specifically to poly(n-hexyl isocyanate) (PHIC) solutions. Deriving the configurational parameters from measurements on chain dimensions in dilute solutions, theoretical calculations are found to satisfactorily match recent experimental results on the molecular weight dependence of the threshold concentration of PHIC in toluene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449780
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular weight dependence of mechanical properties of poly(p,p′-oxydiphenylene pyromellitimide) films (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2487-2495 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical properties, i.e., Young's modulus, elongation, and tensile stress, were determined as functions of the molecular weight for films of poly(oxydi-p-phenylene pyromellitimide) prepared by thermal cyclization of the precursor poly(amic acid). The molecular weights of the samples were controlled by the monomer stoichiometry employed for the solution condensation of pyromellitic dianhydride and p,p′-oxydianiline. Weight-average molecular weights were determined by light scattering of the precursor poly(amic acid) as well as the fully cyclized polyimide. The elongation-at-break is most sensitive to the molecular weight, undergoing a rapid increase at Mw ⋍ 8000 and reaching a limiting value of about 60% for Mw 〉 20,000.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090251205
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