The Synthesis of Thermally Stable Polymeric Azomethines by Polycondensation Reactions

The relationship of the thermal stability of a polymer to its chemical structure has been discussed in several papers [2,40,63,105]. Maximum thermal stability in polymers is usually obtained when: 1. Thermally unreactive ring structures constitute a major portion of the polymer composition. 2. Maximum use is made of resonance stabilization. 3. High bond energy exists between the atoms in the chain. 4. Cohesive energy density is high from (a) chain length, (b) crystallinity, (c) Van der Waals' forces. High-resonance-energy structures can be obtained by use of appropriate aromatic or heterocyclic groups; their thermal unreactivity can be estimated from the thermal reactivity data of Lewis [73]. Most of the available bond-energy values have been determined from studies of small molecules in the gaseous or liquid state.