Photodegradation of Polyimides. 5. An Explanation of the Rapid PhotolyticDecomposition of a Selected Polyimide via Anhydride Formation

摘要

The photolytic decomposition in air of a polymide film based on a dianhydride anda diarylamine with hexafluoroisopropylidene 6F bridging groups is extremely rapid leading to efficient chain cleavage and subsequent photooxidative decomposition. Relatively short photolysis times with an unfiltered medium pressure mercury lamp are required to give a clean photoablation process of the 6F-6F polyimide films in the air. IR difference spectroscopy shows the appearance of anhydride groups on photolysis in air indicating a photooxidation process via decomposition of the arylimide linkage. A photophysical and photochemical analysis of several model N-arylphthalimides indicates that both solvent polarity and electron withdrawing/donating substituents can greatly after all the efficiency of the photolysis process.