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Effects of chemical structure and precursor on optical properties, thermo-mechanical properties, and molecular orientation and order of thin films of stiff aromatic polyimides (1994)

Goeschel, U. ; Lee, H. ; Yoon, D. Y. ; [et al.]

Springer

Colloid & polymer science 272 (1994), S. 1388-1395

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ISSN: 1435-1536

Keywords: Polymides ; optical properties ; thermo-mechanical properties ; chain orientation ; conformational order ; poly(amic acid) ; poly(amic alkyl ester)

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Thin films of rigid poly(p-phenylene pyromellitimide) (PMDA-PDA) and semi-rigid poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the respective poly(amic acid) and poly(amic ethyl ester) precursors, were characterized with respect to their optical, thermomechanical and structural properties. Both polyimides exhibit an unusually large anisotropy between the in-plane and out-of-plane refractive indices, with Δn ranging from 0.198 to 0.216 for PMDA-PDA and from 0.230 to 0.242 for BPDA-PDA, nearly independent of the nature of the initial polyimide precursor, film thickness, and film preparation method. PMDA-PDA films exhibit low coefficients of thermal expansion (CTE's) of 6.5 and 8.2 ppm/δC for the acid-derived and the ester-derived polyimides, respectively. In comparison, the BPDA-PDA films show CTE values of 4.3 and 18.0 for the acid-derived and ester-derived samples, respectively, despite the small differences in their optical anisotropies. Wide-angle x-ray diffraction patterns obtained in reflection and transmission for the various samples reveal a strong in-plane chain orientation for both PMDA-PDA and BPDA-PDA polyimides, with somewhat better intermolecular packing order for the ester-derived polyimide films. These effects of chemical structure and precursor on properties and structures of the polyimide films are discussed in light of recent theoretical considerations of semiflexible polymers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00654169

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Molecular weight dependence of mechanical properties of poly(p,p′-oxydiphenylene pyromellitimide) films (1987)

Volksen, W. ; Cotts, P. ; Yoon, D. Y.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2487-2495

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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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Miscibility behavior and reequilibration of binary poly(amic acid) mixtures (1991)

Ree, M. ; Yoon, D. Y. ; Volksen, W.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1203-1213

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ISSN: 0887-6266

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Five poly (amic acid) solutions based on PMDA-PDA, PMDA-ODA, PMDA-6F, ODPA-ODA, and 6FDA-ODA were prepared in N-methylpyrrolidone at a polymer concentration of ca. 10 wt %. From these five poly (amic acid) solutions, six different binary blends were prepared: PMDA-PDA/PMDA-ODA, PMDA-PDA/PMDA-6F, PMDA-ODA/6FDA-ODA, PMDA-ODA/ODPA-ODA, PMDA-PDA/ODPA-ODA, and PMDA-PDA/6FDA-ODA. These blends were then characterized with respect to miscibility in the ternary state (polyamic acid-1/polyamic acid-2/N-methylpyrrolidone), the condensed state (ca. 70 wt % polymer), and the fully imidized state. All blends except for PMDA-PDA/PMDA-6F yielded homogeneous mixtures in the ternary solution of 10 wt % polymer concentration. The PMDA-PDA/PMDA-6F mixture eventually became homogeneous after 10 days of mixing at room temperature. Upon solvent evaporation (condensed state) and full cure (imidized state) two blends incorporating ODPA-ODA as one of the components exhibited apparent miscibility as evidenced by optical microscopy. The remaining blends exhibited large-scale phase separation upon solvent evaporation with no significant differences in the overall morphology between the condensed and imidized state. However, as in the case of the PMDA-PDA/PMDA-6F ternary system, the morphology in the condensed and imidized state was strongly dependent on the mixing time of the precursor poly(amic acid) components; the phase-separated domain size decreased with increasing mixing time, eventually leading to complete miscibility. These results are discussed with respect to the proposed “polymer-monomer” reequilibration reaction as well as its implications with respect to the preparation of polyimide molecular composites.

Additional Material: 9 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/polb.1991.090291005

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Structure and properties of thin films of binary rodlike/flexible polyimide mixtures (1992)

Rojstaczer, S. ; Ree, M. ; Yoon, D. Y. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 133-143

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ISSN: 0887-6266

Keywords: polyimide mixtures, binary rodlike/flexible, structure and properties of ; blends of rodlike and flexible polyimides, structure and properties of ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Binary mixtures of a rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and a flexible 6F-BDAF polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride and 2,2-bis(4-aminophenoxy-p-phenylene) hexafluoropropane were prepared by solution-blending of the meta-PMDA-PDA poly(amic ethyl ester) and 6F-BDAF poly(amic acid) precursors, followed by solvent evaporation and thermal imidization. Mixtures containing different molecular weights of 6F-BDAF poly(amic acid) were studied. The size scale of the phase separation, as measured by light scattering, is ca. 1 μm or smaller in most cases. The domain size is primarily set by the demixing of the precursor polymers during solvent evaporation, with no significant coarsening observed during the thermal imidization. The observed variation of the domain size with molecular and process parameters such as composition, molecular weight, and film thickness is discussed in terms of the miscibility of the precursor polymers, rate of solvent evaporation, and solidification. Dynamic mechanical thermal analysis and dielectric relaxation measurements indicate that the glass transition temperature of 6F-BDAF is unaffected in all of the mixtures studied, indicating complete demixing of rodlike and flexible polyimides in agreement with theory. X-ray photoelectron spectroscopy results show a strong surface segregation of 6F-BDAF in mixtures containing as low as 10% by weight of the 6F-BDAF component in the bulk. The mixtures with PMDA-PDA as the major matrix component therefore exhibit excellent mechanical toughness, dimensional stability up to 500°C, low coefficients of thermal expansion (〈 ca. 10 ppm/°C), and low dielectric constants (〈3.0). On the other hand, the surface properties of the mixtures are dominated by the flexible 6F-BDAF, resulting in excellent polymer/polymer self-adhesion (lamination) properties between fully imidized films.

Additional Material: 11 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/polb.1992.090300203

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Chain orientation and anisotropies in optical and dielectric properties in thin films of stiff polyimides (1992)

Boese, D. ; Lee, H. ; Yoon, D. Y. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1321-1327

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ISSN: 0887-6266

Keywords: polyimides. stiff, optical and dielectric properties in their films of ; optical anisotropy and chain orientation stiff polyimide thin films ; dielectric properties of stiff polyimide thin films ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Thin films of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the precursor poly(amic acid) on substrates, have been investigated by optical waveguide, ultraviolet-visible (UV-VIS), infrared (IR), and dielectric spectroscopies. The polyimide films exhibit an extraordinarily large anisotropy in the refractive indices with the in-plane index n∥ = 1.806 and the out-of-plane index n⊥ = 1.589 at 1064 nm wavelength. No discernible effect of the film thickness on this optical anisotropy is found between films of ca. 2.1 and ca. 7.8 μm thickness. This large birefringence is attributed to the preferential orientation of the biphenyltetracarboximide moieties with their planes parallel to the film surface, coupled with the strong preference of BPDA-PDA chains to align along the film plane. The frequency dispersion of the in-plane refractive index n∥ is consistent with the results calculated by the Lorentz-Lorenz equation from the UV-visible spectrum exhibiting several absorption bands in the 170-500 nm region. The contribution from the IR absorption in the range 7000-400 cm,-1 computed by the Spitzer-Kleinmann dispersion relations from the measured spectra, adds ca. 0.046 to the in-plane refractive index n∥. Tilt-angle-dependent polarized IR results indicate nearly the same increase for the out-of-plane index n⊥. Application of the Maxwell relation then leads to the out-of-plane dielectric constant ε⊥ ≃ 2.7 at 1.2 × 1013 Hz, as compared with the measured value of ca. 3.0 at 106 Hz. Assuming this small difference to remain the same for the in-plane dielectric constants ε∥, we obtain a very large anisotropy in the dielectric properties of these polyimide films with the estimated in-plane dielectric constant ε∥ ≃ 3.4 at 1.2 × 1013 Hz, and ε∥ ≃ 3.7 at 106 Hz. © 1992 John Wiley & Sons, Inc.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/polb.1992.090301203

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