The structure of poly-2,5-benzoxazole (ABPBO) and poly-2,6-benzothiazole (ABPBT) fibers by X-ray diffraction
| Autor: | W. Wade Adams, Elisa M. Cross, Albert Fratini, Joseph F. O'brien |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
Materials science
Polymers and Plastics General Chemistry Crystal structure Benzoxazole Dihedral angle Condensed Matter Physics chemistry.chemical_compound Crystallography symbols.namesake Synthetic fiber chemistry X-ray crystallography Materials Chemistry symbols Orthorhombic crystal system Fiber van der Waals force |
| Zdroj: | Journal of Macromolecular Science, Part B. 24:159-179 |
| ISSN: | 1525-609X 0022-2348 |
| Popis: | The determination of the crystalline structure of oriented fibers of poly-2,5-benzoxazole (ABPBO) and poly-2,6-ben-zothiazole (ABPBT) is described. Both unit cells are metrically orthorhombic, with the parameters: a = 6.061 (17), b = 3.384 (13), c (fiber axis) = 11.575 (6) A for ABPBO; and a = 6.044 (6), b = 3.417 (7), c (fiber axis) = 12.194 (18) A 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 interactions. A plausible disorder model which involves defects in chain direction is presented. Refinement of a static disorder model for ABPBO in which 50% of the chains have their chain directions reversed leads to a lower R residual and sum of constraints. |
| Databáze: | OpenAIRE |
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