Star-Shaped Azo based Dipolar Chromophores: Design, Synthesis, Matrix Compatibility, and Electro-optic Activity

Three new azo-benzene based push-pull chromophores with dendritic architecture were synthesized as active materials for electro- optic applications. These chromophores were synthesized in 6 to 7 synthetic steps with an overall yield of around 80% and high purity. UV-Vis spectroscopy showed significant influence of the transient dipole moment to the observed r33 values. These chromophores were stable to photochemical oxidation in ambient light and air. The electrical poling conditions were optimized for each chromophore as the Tg of the composite material varied significantly. The highest EO coefficient achieved was 22 -25 pm/V at 1550 nm wavelength. STEM analysis of the blends enabled the correlation of the activity of these large chromophores with the blend morphology. Amorphous polycarbonate host effectively disperses the chromophores in 2-20 nm aggregates in the active materials. However, macrophase separation into 200-500 nm aggregates was observed in the methacrylate host matrix.