Synthesis and characterization, second-order nonlinear optical and photorefractive properties of new multifunctional polysiloxane with broad optical transparent pentafluorophenyl azo chromophore

A new polysiloxane P1 with pendant carbazoly groups and a high density of the pentafluorophenyl azo chromophore as side chain was synthesized in moderate yield by two successive postfunctionalization reaction including Vilsmeir formylated reaction and Knoevenagel condensation. Its structure was verified by 1H NMR, IR, and UV-Vis spectra. The polymer P1 exhibited good solubility in common organic solvents and was thermally stable up to 282 °C. The maximum absorption appeared at about 407 nm for P1 in THF, which was blue-shifted about 87 nm compared to the corresponding polysiloxane P2 with a well-known nitro acceptor azo chromophore, resulting in a wider transparency window. The value of the NLO coefficient d33 of P1 thin film, measured by in situ second harmonic generation (SHG), was 11.9 pm/V. Preliminary photorefractive experiments showed that P1 obtained diffraction efficiency of 78% and a time constant of 1.19 sec.