Large and highly stable photoinduced birefringence in poly(amideimide)s with two azochromophores per structural unit

• Four photosensitive and processable poly(amideimide)s with azobenzene chromophores were synthesized.
• Azofunctionalized polymers contained two chromophores in the polymer repeating unit.
• High level of photoinduced birefringence (0.06) was obtained.
• The generated birefringence showed extraordinary stable behavior.

We present a series of novel poly(amideimide)s containing two covalently bonded azobenzene chromophores in the polymer repeating unit. The chromophores possess different substituent in para position such as fluorine, hydroxyl, methyl or do not contain any of them. The synthesized polymers were characterized by 1H NMR, FTIR spectroscopies and elemental analysis. The polymers showed high glass transition temperatures (250–280 °C), which were significantly separated from the temperatures of thermal decomposition (345–590 °C). The photoinduced birefringence measurements were performed for continuous wave irradiation at 405 nm. A very large, as for polyimides, birefringence of 0.06 was observed with the growth dynamics dependent on the chromophore substituent. The generated birefringence exhibited an exceptionally low relaxation. Apart from the poly(amideimide) with the methyl substituent it decreased by only 1.5% just after switching off the excitation light, and maintained its level during the next 500 s.