Synthesis and macroscopic second-order nonlinear optical properties of poly(ether imide)s containing a novel two-dimensional carbazole chromophore with nitro acceptors

Taking advantage of the multifunctional characteristics of carbazole along with rational molecular design, a two-dimensional carbazole chromophore with strong nitro acceptors was synthesized by a facile synthetic route. A first molecular hyperpolarizability of 163 x 10(-30) esu was acquired through solvatochromic methods. By doping of the chromophores into an organosoluble poly( ether imide), a series of guest-host NLO polymers were acquired. A high doping level up to 20 wt% was obtained without observing aggregation of NLO chromophores. The compatibility between chromophore and poly( ether imide) was also investigated by SEM and extraction experiments. In terms of compatibility, the molecular weight distribution of the polymer plays an important role. The second harmonic coefficients (d(33)) for the NLO-active poly(ether imide) s range from 7 to 23 pm V-1 depending on the doping level. The effect of two-dimensional structure on the NLO temporal stability was investigated by tracing the second harmonic coefficient as a function of time. Moreover, the relaxation behavior of the NLO systems was further examined by dielectric analysis. Large rotational cone volumes give the two-dimensional chromophore excellent orientational stability when the temperature approaches the glass transition temperature observed from DEA.