Thermal stability and optical properties of aromatic polyimides containing side-substituted azobenzene groups

Abstract

Aromatic azopolyimides based on 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride and aromatic diamines containing substituted azobenzene group have been studied regarding their thermal and photooptical properties. The thermal analysis showed that the decomposition of these polymers takes place in two or three stages. The optical properties of the investigated polymers have been analyzed by transmission and reflectivity measurements within the spectral range of 200–2500 nm. Temperature dependence of absorption coefficient has been found on the basis of “in situ” transmission measurements, during annealing of thin films up to 300°C. It turned out that this process did not change the conjugation of polymer chain but caused a slightly more, irreversible structural disorder.