TGA–MS degradation studies of some new aliphatic–aromatic polybenzimidazoles

The degradation of a series of polybenzimidazoles containing metylene groups in the chain was studied by TGA and MS. On heating the polymer derived from m ‐phenylenediacetic acid and 3,3′‐diaminobenzidine to about 560°C in argon, partial fast decomposition into a solid sublimate was observed. The sublimate consisted of a mixture of fractions derived from the breaking of the chain at the methylene bonds. These methylene groups can be preoxidized at 250°C to carbonyl groups, eliminating thereby this mode of decomposition. At temperature higher than 560°C, gaseous products similar to those of the corresponding all‐aromatic PBI are obtained.