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.