ISSN:
1436-2449
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Summary Two polybenzoxazoles possessing -CH2CH2-units in the backbone have been examined for their unusual thermal depolymerization behavior. In contrast to other polybenzoxazole s which displayed gradual TGA weight losses from 500–1000°, both the 2,5- and 2,6-dimethylene polymers displayed catastrophic degradation between 450° and 500° involving more than 50% weight loss over a 50° range (5 minutes of a 100 minute cycle). The pyrolysis-GC-MS data for the 2,5-isomer displayed numerous stable thermolysis products, several of which possessed parent m/z values of 289 consistant with dimers of the repeat unit. Thermal depolymerization in a sublimation apparatus gave “sublimed” polymer almost identical with the starting material. These results suggest that one of the major depolymerization pathways involves formation of a diradical intermediate similar to that observed for [2.2]-paracyclophane. Cyclodimerization (prior to GC separation) apparantly competes with polymerization that is favored in the condensed phase region of the sublimation experiment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00254223
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