The Structure of Poly-2,5-Benzoxazole (ABPBO) and Poly-2,6-Benzothiazole (ABPBT) Fibers By X-Ray Diffraction
Final rept. 1 May-31 Dec 1984
DAYTON UNIV OH DEPT OF CHEMISTRY
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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.
- Polymer Chemistry