The synthesis and optical properties of novel fluorinated polyimides incorporated with highly electro-optic active thiazole and benzothiazole based chromophores

Novel, non-linear optical fluorinated polyimides were prepared by the Mitsunobu reaction of hydroxyl-containing hetarylazo chromophores with hydroxyl polyimides. Their structures were verified by FT-IR, 1H NMR, UV–Vis spectra, elemental analysis and gel permeation chromatography. The resulting amorphous polyimides exhibited good solubility and can be easily spin-coated into thin films with good optical quality. The high electro-optic coefficients (r33) obtained for the films of poled polyimides were attributed to the introduction of hetarylazo chromophores with large hyperpolarizability within the polyimides. The polyimides possess high glass transition temperature (201–210 °C) and therefore showed excellent temporal stability, retaining 88% of their initial non-linear optical response at 110 °C for >200 h. Low optical losses in the range of 1.9–2.3 dB cm−1 at 1550 nm were observed for the polyimides and the values of thermooptic coefficients ranged from −1.680 × 10−4 to −2.008 × 10−4/°C.