Molecular order in condensed states of semiflexible poly(amic acid) and polyimide

Abstract

The molecular order in condensed states of the aromatic poly(amic acid) (PAA) poly(4,4'oxydiphenylenepyromellitamic acid) and the resulting polyimide (PI) poly(4,4'-oxydiphenylenepyromellitimide) obtained by heating PAA films was determined from wide-angle X-ray diffraction studies. PAA chains in films containing solvents of ~30% by weight exhibit parallel alignment and correlated (smectic-like) lateral packing of highly extended chain segments, as shown by the appearance of a diffraction peak due to the intramolecular periodicity of ~14 Á. Upon imidization and removal of solvents by heating at 200 °C, this molecular order is preserved and slightly improved in the resulting PI films. Further improvement in order occurs upon annealing PI films at temperatures above ca. 300 °C, with the details of changes depending strongly on the initial orientation. In all PI samples, however, the high-angle diffraction patterns in the region of the scattering vector s (=(2 sin )/ ) > 0.35 Á-1 are matched very closely by the theoretical curve calculated for a single repeat unit, thereby indicating the absence of any appreciable long-range crystalline order in the thermally imidized PI films. The ramifications of such molecular order in condensed states of PAA (which cannot crystallize due to the meta-para isomers in the pyromellitamic acid unit) and PI are discussed in light of recent theoretical developments in the statistical thermodynamics of semiflexible polymers as well as some unique characteristics exhibited by this polyimide.

Adhesion of poly(4,4′-oxydiphenylene pyromellitimide) to copper metal using a polymeric primer: Effects of miscibility and polyimide precursor origin

“…7, the PAEBI film revealed only one broad peak in both transmission and reflection modes, indicating that the polymer is amorphous while the PMDA-ODA PI film showed three distinctive diffraction peaks over 3 -40 8 (2h). For the PMDA-ODA PI, the first peak at the low angle region can be indexed as (002) 3,22,23) . This peak is relatively stronger in the transmission pattern than in the reflection pattern, indicating that the polymer chains are aligned favorably in the film plane rather than randomly.…”

Linear Optical Anisotropy in Aromatic Polyimide Films and Its Applications in Negative Birefringent Compensators of Liquid-Crystal Displays

“…This phenomenon has been defined as "in-plane orientation" (1)(2)(3)(4)(5). Recently, it has been recognized that such anisotropic structure leads to anisotropic thermal, mechanical, dielectric and optical properties along the in-plane and out-of-plane directions (5).…”

“…Since aromatic polyimide molecules commonly tend to align parallel to the film surface during the film forming process (1)(2)(3)(4)(5), the in-plane refractive index is thus larger than the out-ofplane refractive index. The degree of in-plane orientation and the resultant extent of LOA in the films can be estimated readily using refractive index measurements.…”

“…One of the most widely used methods is wide angle X-ray diffraction (WAXD) experiments (1)(2)(3)(4). …”

Imide?Dimethylsiloxane block copolymers: Design and synthesis of a permanent buried oxygen ion etch barrier

“…1 Such insulating materials must be desirable properties reflect the high degree of moable to withstand the high temperature associlecular packing. [7][8][9][10] For instance, with PMDA/ ated with the processes used to deposit metal lines ODA polyimide, a local smecticlike ordering is and join chips without any degradation, outgasfound. These rigid polyimides are generally apsing, or dimensional change.…”