Degradation of polyethers containing in‐chain alicyclic ring structures

The degradation of polymers prepared by ring‐opening polymerization of methyl substituted 7‐oxabicyclo‐[2.2.1]‐heptanes has been investigated. The thermal stability was found to be dependent upon the molecular weight up to a limiting value. For the polymers with high molecular weights the thermal stability with regard to initial weight loss was found to be comparable to that of the aromatic analog polyphenyleneoxide (PPO) when the degradation occurs in inert atmosphere. The thermal degradation proceeds differently for the different polymers and while PPO carbonizes with a substantial residue, the alicyclic polymers do not discolorize during a process where quantitative conversion to volatile products takes place. Gas‐liquid chromatography established that the monomer could not be found among the degradation products. The suitability of utilization of a combination of TGA and GPC measurements for studying the course of the degradation is demonstrated. Oxidative degradation was found to proceed at a much faster rate than that of the purely thermally induced process for both alicyclic and aromatic polymers. However, for PPO it was found that 20–30% of the initial weight is lost very quickly in an exothermic reaction after which the weight loss become very slow. The oxidative weight loss for the alicyclic polymers is essentially linear with time and occurs with a rate which is slower than the initial rate for PPO.