Synthesis and nonlinear optical properties of novel fluorinated polyimides with thiazolylazo chromophores for electrooptic devices

摘要

A series of novel fluorinated polyimides second-order nonlinear optical (NLO) materials were synthesized from poly(hydroxy-imide)s, followed by the Mitsunobu reaction with NLO thiazolylazo chromophores. The polyimides prepared were characterized by IR, UV-vis, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetric analysis (DSC) and X-ray diffraction (XRD). These NLO polyimides possess highglass transition temperature (T_g) in the range of 180-210 °C with thermal stability up to 288 °C. The electro-optic coefficients (r_(33)) at the wavelength of 1550nm for polymer thin films poled were measured by the attenuated total reflection (ATR) method. The r_(33) values of the polyimides 1a and 2a containing thiazolylazoaniline chromophore are better than that of the polyimides 1b and 2b attached thiazolylazopyrimidine chromophore, due to the thiazolylazoaniline chromophore having large hyperpolarizability in contrast to the thiazolylazopyrimidine chromophore. Low optical losses (1.0-1.4 dB/cm at 1.55 μm), which were measured via an immersion technique have been observed for these polymers. The polyimides demonstrate an excellent combination of thermal stability, electrooptic (EO) coefficients and optical loss, and therefore they are suitable for EO applications.