Extended chain conformational preference of solid films of poly(2,6-benzoxazole) processed from Lewis acid coordination complexes
- Univ. of Rochester, NY (United States)
Polybenzoxazoles such as poly(2,6-benzoxazole)(2,6-PBO), poly(2,6-benzothiazole)(2,6-PBT) and poly(2,5(6)-benzimidazole) are semi-flexible, high temperature, and high modulus polymers which have been of wide interest as the matrix components of molecular composites. These polymers and their rigid-rod relatives polybenzobisazoles(PBZT, PBO, etc) also exhibit interesting electroactive and photoactive properties. As previously shown for rigid-rod polybenzobisazoles, we have found that the semi-flexible polybenzoazoles are soluble in Lewis acid (e.g. GaCl{sub 3}, AlCl{sub 3})/nitromethane solvent systems from which films and fibers could be processed. Remarkably, 2,6-PBO films prepared by complexation mediated processing from Lewis acid/nitromethane solutions of the polymer exhibit the extended chain (trans) conformation as evidenced by optical absorption and photoluminescence spectroscopies. In contrast, 2,6-PBO films prepared from formic acid/methanesulfonic acid(FA/MSA) solvent am predominantly of cis-conformation. The origin of this extended chain conformation preference of 2,6-PBO films prepared from Lewis acid/nitromethane solutions lies in the stereochemical control exerted by Lewis(MX{sub 3}) coordination to the imine nitrogens of 2,6-PBO resulting in an all-trans conformation after film processing and decomplexation. Since the trans- and cis-(2,6-PBO) have dramatically different solid state properties such as optical absorption and luminescence, our results demonstrate how a high degree of control of solid state structure and properties can be achieved by novel polymer processing.
- OSTI ID:
- 602814
- Report Number(s):
- CONF-961108-; TRN: 98:001968-0004
- Resource Relation:
- Conference: Annual meeting of the American Institute of Chemical Engineers (AIChE), Chicago, IL (United States), 10-15 Nov 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 First joint topical conference on processing, structure and properties of polymeric materials; PB: 594 p.
- Country of Publication:
- United States
- Language:
- English
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