Accession Number:

ADA181695

Title:

The Structure of Poly-2,5-Benzoxazole (ABPBO) and Poly-2,6-Benzothiazole (ABPBT) Fibers By X-Ray Diffraction

Descriptive Note:

Final rept. 1 May-31 Dec 1984

Corporate Author:

DAYTON UNIV OH DEPT OF CHEMISTRY

Report Date:

1985-07-01

Pagination or Media Count:

32.0

Abstract:

The determination of the crystalline structure of oriented fibers of poly-2,5-benzoxazole ABPBO and poly-2,6-benzothiazole ABPBT is described. Both unit cells are metrically orthorhombic, with the parameters a6.0617, b3.38413, c fiber axis11.5756 A for ABPBO, and a6.0446, b-3.477, c fiber axis12.19418A for ABPBT. The fiber repeat consists in each structure of two fused ring groups arranged in a planar, zigzag conformation. The conformational torsion angle and orientation of chains within the unit cells are derived from a linked-atom least squares refinement technique. Polymer chains pack laterally through van der Waals interations. A plausible disorder model which involves defects in chain direction is presented. Refinement of a static disorder model for ABPBO in which fifty percent of the chains have their chain directions reversed leads to a lower R residual and sum of constraints. The determination of the crystal structures of these two polymers is important for understanding of the processing, properties and morphology of high strength, high modulus fibers of these materials. Keywords Polybenzoxazole Units Cell Aromatics Heterocyclics Polymers.

Subject Categories:

  • Polymer Chemistry
  • Plastics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE