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Molecular Packing and Crystalline Order in Polybenzobisoxazole and Polybenzobisthiazole Fibers

Published online by Cambridge University Press:  26 February 2011

Albert V. Fratini ,
P. Galen Lenhert ,
Timothy J. Resch  and
W. Wade Adams
Albert V. Fratini
Affiliation:
Department of Chemistry, University of Dayton, 300 College Park, Dayton, OH 45469
P. Galen Lenhert
Affiliation:
Department of Physics, Vanderbilt University, Nashville, TN 37235
Timothy J. Resch
Affiliation:
Department of Chemistry, University of Dayton, 300 College Park, Dayton, OH 45469
W. Wade Adams
Affiliation:
Wright Research and Development Center, Materials Laboratory, WPAFB, OH 45433–6533
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Abstract

The structures of poly(p-phenylenebenzobisthiazole) (PBZT) and poly(p-phenylenebenzobisoxazole) (PBO) fibers have been investigated by fiber diffraction techniques. d-spacings were obtained from equatorial and meridional scans recorded on a four-circle diffractometer. Intensity data were derived from x-ray rotation patterns taken on Weissenberg and vacuum cylindrical cameras. Unit cells were found to be monoclinic and non-primitive, each containing two chains per cell of dimensions a = 11.79(2), b = 3.539(5), c = 12.514(9) A, γ = 94.0(2)o for PBZT; and = 11.20(1), b = 3.540(2), c = 12.050(3) Å, γ = 101.3(1) for PBO. The fiber axes correspond to c. The conformational torsion angle between the bisthiazole and phenylene units and the orientation of chains within the unit cells were obtained from a ‘linked-atom least-squares’ (LALS)refinement procedure. A packing model is proposed for each polymer in which two independent molecular chains are displaced longitudinally by discrete rather than random increments. Primitive unit cells (Z = 1), besides requiring perfect axial registry of molecular chains, suffer from the occurrence of short intermolecular contacts and are rejected from further consideration.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 134: Symposium J – Materials Science and Engineering of Rigid-Rod Polymers , 1988 , 431
Copyright
Copyright © Materials Research Society 1989

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References

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