Molecular aggregation of solid aromatic polymers. I. Small‐angle x‐ray scattering from aromatic polyimide film

Abstract

Molecular aggregation in a commercial polyimide film, Du Pont Kapton, was investigated by small‐angle x‐ray scattering (SAXS). From the analysis of the desmeared SAXS curve, it is concluded that aggregation in the Kapton film can be elucidated in terms of a two‐phase structure having electron density fluctuations within the phases. For comparison with the molecular aggregation in Kapton, molecular aggregation in polyimides synthesized in our laboratory was also investigated. It was found in this case that molecular aggregation is controlled by the initial imidization temperature. Molecular aggregation of polyamic acid and polyimide cyclized at a low temperature gives amorphous structures. On the other hand, molecular aggregation of polyimide cyclized at high temperatures gives two‐phase structures like that of Kapton film. The SAXS curve for a polyimide having the two‐phase structure shows a peak due to interference between ordered regions. The two‐phase structure of the polyimide can be explained in terms of a one‐dimensional model. The more ordered phase is produced at the higher initial imidization temperature. The relative density difference between two phases is only a few percent for polyimide films cyclized at high temperatures. This result shows that the two‐phase structure of aromatic polyimide differs essentially from that of ordinary crystalline polymers.

Water‐sorption behaviors of poly(3,4′‐oxydiphenylene pyromellitimide) films depending on the thickness variation

“…The isotherms were apparently well fitted to a Fickian diffusion model, irrespective of relative humidity and morphological heterogeities because of the ordered and disordered phases. 26,27 It shows that the sorption behavior of small molecules in polymers should be patterned after a Fickian diffusion model, well below the glass-transition temperature of the host. 28 -31 Thus, the diffusion coefficient and water uptake were simulated with the following equation, which has been driven for an infinite slab with a constant surface concentration by Crank and Park 28,29 :…”

Grazing incidence wide angle x-ray scattering at the wiggler beamline BW4 of HASYLAB

“…Commonly investigated material systems include conjugated polymers, block copolymers, lipids, and magnetic or semiconducting materials in a wide variety of applications. [39][40][41][42][43][44][45][46] To establish and prove the feasibility of GIWAXS at BW4, we applied this technique to a variety of different samples. Here we present the sample of a thin film of the conjugated and conducting polymer poly͑3-octylthiophene͒ P3OT on top of a precleaned glass slide.…”

Novel phenylethynyl-terminated PMDA-type polyimides based on KAPTON backbone structures derived from 2-phenyl-4,4′-diaminodiphenyl ether

“…The PI(PMDA/4,4 0 -ODA) film showed a significant annealing effect caused by molecular ordering. 24,25 In contrast, PI(PMDA/p-ODA) clearly showed not only a high T g at 325 1C but also a remarkably large drop in E 0 from 10 9 to 10 7 Pa (rubbery plateau region) above T g . These dynamic tensile behaviors of PI(PMDA/p-ODA) arose because the pendant phenyl group of p-ODA restricted the conformational change of PMDA/4,4 0 -ODA backbone structure, because of its rotational inflexibility of ether linkage and the intramolecular/intermolecular interactions of PI chains and because of its nonplanar and bulky steric hindrance.…”