ISSN:
0887-6266
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The deformation of the aromatic polyimide poly{N,N′-bis(phenoxyphenyl)-pyromellitimide} (PMDA-ODA) has been investigated by x-ray scattering. PMDA-ODA, which exhibits a smecticlike ordering in the bulk can be elongated up to 70% at room temperature without a distinct yield point. Under strain, the diffraction pattern of the intramolecular spacing occurring at a Bragg spacing of 15.4 Å is elliptical. The ellipticity shows that the molecule changes its repeat distance along the chain axis. This may result from bond angle and bond length distortions. Consistent with this is a rapid recovery well below the glass transition temperature where all but 20% strain is recovered. This localized extension, however, cannot account fully for the macroscopic deformation applied, and, as such, a global orientation of the chains occurs, as evidenced by the arcing of the diffraction profiles. The retention of the intrachain reflection indicates that bundles of chain segments ordered in a smectic fashion orient as a unit maintaining a lateral chain-segment alignment. Finally, the scattering vector at which a small-angle scattering reflection occurs was found to be correlated to the coherence length determined by a Scherrer analysis of the ca. 15.4 Å intramolecular reflection. As the strain increased, the intensity and spacing of the small-angle scattering reflection increased parallel to the stretching direction and decreased perpendicular to this. This suggests that the origin of the small-angle scattering reflection arises from electron density fluctuations along the chain axis, as is typically seen in semicrystalline polymers.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1987.090250513
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