Thermally stable nonlinear optical polymers based on polyimides substituted with chromophores containing julolidine moiety

We designed and synthesized a NLO chromophore adopting the concept of shape modification as well as possessing high thermal stability. The chromophore was featured by a phenylene ring as a conjugation bridge, a bulky alkyl chain attached on the side of the conjugation bridge, and julolidine moiety as an electron donor. The NLO chromophore was attached to the polyimide as a side chain, resulting in thermally durable NLO polymers. On set decomposition temperature of the NLO chromophore was measured 330°C in TGA analysis. The NLO polymer exhibited high glass transition temperature of 150°C and was thermally stable up to 250°C. The polymer was quite soluble in common solvents and produced an optical quality film by spin-coating. The electro-optic coefficient of the film was measured using 1.55 μm laser source, giving as high as 30 pm/V at the poling condition of 150°C and 1 MV/cm.