| Popis: |
A spectrophotometric study was made of absorption in the range of 220–500 nm of poly(N,N′-bis-(phenoxyphenyl)pyromellitimide), its prepolymer and solutions of a number of model compounds. Proposals were made for the interpretation of absorption bands in the spectrum of the polyimide. It was established that the prepolymer shows blue fluorescence, while polyimide shows none. The absence of fluorescence is hypothetically explained by the high efficiency of intercombination conversion, which is due to the existence of a low level of triplet state of nρ∗ type. A spectrophotometric method was developed for evaluating the degree of cyclization. |
