Quantum chemical PM-3 study of the thermal stability of heterocyclic fragments of heteropolymers, 1. Five-membered heterocycles: Azoles and imides

✍ Scribed by Vladimir A. Zubkov; Alexander V. Yakimansky; Svetlana E. Bogdanova; Vladislav V. Kudryavtsev

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 557 KB
• Volume: 3
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.1994.040030217

✦ Synopsis

Abstract

Semiempirical PM‐3 calculations of the mechanisms of the decomposition of oxazole and maleimide have been carried out. It has been shown that thermal decomposition of the considered heterocycles proceeds via a consecutive breaking of two ring bonds, the breaking of the second bond being the rate‐determining step. Both an activation barrier of heterocycle decomposition and its dissociation energy (E~D~) can be used as a measure of heterocycle thermal stability. The correlation between E~D~ values of azole and imide containing model compounds and the initial degradation temperatures of corresponding heteropolymers makes it possible to clarify some essential features of the thermal degradation of polyazoles, polybenzazoles and polyimides.