Preparation and thermal properties of polyquinazolone containing 4-substituted phenyl groups on the quinazolone ring

Polyquinazolones containing 4-substituted phenyl groups (H, Cl, CH₃, CH₃O, NO₂) on the quinazolone ring were synthesized in m-cresol and their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss in nitrogen and air. Polyquinazolones were synthesized with intrinsic viscosities in the range of 0.2–0.7 dL/g when phosphorus pentoxide was used as a catalyst. In TGA studies, there was a difference in the initial decomposition temperature of polyquinazolones with varying substituted groups. The introduction of substituted groups reduced oxidative thermal stability of the polymers. Furthermore, the thermal degradation mechanism was investigated by infrared spectrophotometry.