Molecular rearrangement by thermal degradation of poly(oxy-2,6-dimethyl-1,4-phenylene)

Four major phenolic compounds: o-cresol, 2,6-xylenol, 2,4-xylenol, and 2,4,6-trimethylphenol were obtained as monomeric scission products by thermal degradation of poly(oxy-2,6-dimethyl-1,4-phenylene) (polyphenylene ether or PPE) in an inert atmosphere. The structures and contents of dimeric scission products recovered at the same time were more complicated than the monomeric products. The quantitative analyses of both scission products were used to elucidate the degradation mechanism. The chemical structures of the scission products suggested that the ether bridges in the main chain are partially converted to methylene bridges previous to the thermal degradation. The composition of the scission products can be explained by the assumption that the methylene bridges between benzene rings cleave almost in the same probability in spite of the circumstances. The structure of the polymer after heat treatment is much more relevant to the thermal degradation than that of the polymer before heat treatment.