Photodegradation of polyimides. II. Thermal property changes of polyimides based on a hexafluorinated dianhydride

Abstract Polyimides based on a hexafluorinated dianhydride decrease in thermal and thermal‐oxidative stability upon photolysis with an unfiltered medium pressure mercury lamp source in air. Additionally, the glass transition of photolyzed polyimides containing the hexafluorinated moiety is lowered with increasing photolysis time. By contrast, pyromellitic‐dianhydride‐based polymers are relatively thermally stable even after prolonged photolysis under similar conditions.