Synthesis and characterization of a new photoconducting poly(siloxane) having pendant diphenylhydrazone for photorefractive applications

A new photoconducting polymer, diphenyl hydrazone-substituted polysiloxane, was successfully synthesized by the hydrosilylation method and characterized by FT-1R, ¹H-NMR, and ²⁹Si-NMR spectroscopy. The glass transition temperature (T_g) of the polysiloxane having pendant diphenyl hydrazone was ca. 62°C, which enabled a component of a low-T _g photorefractive material to be prepared without the addition of any plasticizers. This polysiloxane, with 1 wt% of C₆₀ dopant, showed a high photoconductivity (2.8 × 10^-12 S/cm at 70 V/μm) at 633 nm, which is necessary for fast build-up of the space-charge field. A photorefractive composite was prepared by adding a nonlinear optical chromophore, 2-{3-[2-(dibutylamino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenylidene} malononitrile, into the photoconducting polysiloxane together with C ₆₀. This composite shows a large orientation birefringence (Δn = 2.6 × 10^-3 at 50 V/μm) and a high diffraction efficiency of 81 % at an electric field of 40 Vf/μm.