Nonlinear optical polyimides consisting of chromophore-containing dendrons with site-isolation effect



To investigate the dendritic structure effects on the electro-optical (EO) coefficients and thermal stability of the nonlinear optical (NLO) active materials, a bifunctional compound, IDD (4-isocyanato-4′(3,3-dimethyl- 2,4-dioxo-acetidino)-diphenylmethane) was used as a building block to synthesize a series of novel NLO chromophore-containing dendritic structures including Generation 0.5 (G0.5) to Generation 3 (G3). The glass transition temperatures (Tg) of G1–G3 dendrons were in the range of 76–116°C, whereas only the G0.5 dendron exhibited a melting temperature (Tm), 98°C. Moreover, a series of NLO-active guest–host systems ranging from polyimide-G0.5 (PI-G0.5) to polyimide-G3 (PI-G3) were prepared by blending 20 wt% chromophore-containing dendron with a high Tg polyimide. EO coefficients ranged from 6.1 to 12.9 pm/V. The r33/dye content ratio increased with increasing generation of dendron-containing polyimide samples. Particularly, the improvement in r33/dye content ratio of PI-G2.5 sample tripled as compared to that of the guest–host sample with Disperse Red 1. Excellent temporal stability of PI-G0.5 and PI-G1.5 at 80°C was obtained. Moreover, waveguide properties for NLO polymers containing higher generation dendrons (3.1–3.6 dB/cm at 830 nm) were also obtained. Copyright © 2008 John Wiley & Sons, Ltd.