“…21 Despite significant advances in the chemistry of azo-based PAEs, the importance of azo-containing PAEs with perfluorinated aromatic fragments (FPAEs) is somewhat neglected in the literature. However, azo-free FPAEs themselves possess unique properties that are essential for effective functioning in modern high-tech applications, particularly in microelectronics, [22][23][24] optical telecommunications, [25][26][27] and fuel cell membrane technology. [28][29][30] In addition to the expected improvement in chemical and thermal stability, the introduction of perfluorinated aromatic units into the polymer structure allows for upgrading their optical and electro-optical properties, particularly to reduce refractive index and optical losses and to increase hyperpolarization.…”