Photochemistry of a benzophenone-containing bisimide: a model for inherently photosensitive polyimides

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 1988-07, Vol.44 (1), p.99-110
• Main Authors: Scaiano, J.C., Becknell, A.F., Small, R.D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Physicochemistry of polymers; Polymers and radiations; Properties and characterization
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/1010-6030(88)85009-3

The photochemistry of bisimide II has been studied in solution by conventional means as well as by time-resolved laser techniques. Compound II, the adduct of benzophenonetetracarboxylic dianhydride and 2 equivalents of 2-isopropylaniline, was designed as a model for inherently photosensitive, solvent-soluble polyimides — whose photochemistry is not well understood. A low temperature phosphorescence spectrum of matrix-isolated II, along with other results, indicates that the reactivity of II following photon absorption (300 – 365 nm) is due to its lowest n,π * triplet state. Triplet II behaves in a similar fashion to triplet benzophenone, being efficiently quenched by 1,3-dienes and photoreduced by compounds containing labile CH bonds. The absorption spectrum of the intermediate ketyl in the photoreduction was observed, and phosphorescence quenching rate constants for excited II determined in the presence of 2-propanol or triethylamine. The equation for determining quenching rate constants in a “gated” quenching experiment was derived and differs from that used in normal Stern-Volmer studies.