Photorefractivity of hyperbranched polyisophthalate endcapped with pendant carbazolyl and azobenzene groups

A novel hyperbranched polyisophthalate containing pendant carbazolyl and azobenzene groups at the terminals was synthesized, and its photorefractivity has also been evaluated by the effective electro-optic (EO) coefficient, two-beam couple (TBC) coefficient, diffraction efficiency and photorefractive (PR) response time. This PR polymer has a low glass transition temperature of 21 °C without any extra plasticizer added, which provides a necessary free volume for EO chromophore reorientation during the recording process at room temperature. The obtained PR film exhibited an effective EO coefficient of 30 pm V−1, a TBC coefficient of 59 cm−1, a diffraction efficiency of 17%, and a modulation index of 1.67 × 10−3 at the wavelength of 632.8 nm with an applied electric field of 80 V μm−1 at room temperature. The TBC coefficient was found to be beam-intensity dependent, compared with what is found in inorganic crystals. Moreover, a fast PR response time of 10 ms was deduced at an erasing beam intensity of 1.0 W cm−2.