Synthesis and characterization of photorefractive polymers with triphenylamine unit and NLO chromophore unit on a side chain

Acrylate‐type copolymers (TPA‐DCV) consisting of triphenylamine (TPA) unit as a hole transport agent and dicyanovinyl aniline (DCV) as a second‐order nonlinear optical (NLO) chromophore on a side chain were synthesized. The polymers showed good solubility and sufficient morphological stability after film formation. The diffraction efficiency and gain coefficient increased as glass transition temperature decreased TPA‐DCV composite doped with fullerene (C₆₀) and dibutyl phthalate had a high photoconductivity of 5.1 × 10⁻¹² S/cm at the applied electric field of 50 V/µm. Diffraction efficiency and response rate were measured as functions of the parameters determining the photoconductivity (e.g. applied electric field, the density of the photocharges generated and writing beam intensity). The maximum diffraction efficiency and gain coefficient were 12.9% and 64 cm⁻¹, respectively, at an applied electric field of 80 V/µm. The maximum response time of 700 msec was obtained at the applied electric field of 80 V/µm. Photoconductivity, response rate and diffraction efficiency increased with the increase of the applied electric field. Field dependence of the response rate is attributed to the charge generation efficiency and/or the drift mobility. A similar power dependence of the photoconductivity and the response rate on the writing beam intensity was observed. The response rate and diffraction efficiency showed a good linear relationship with the logarithm of the photoconductivity. Copyright © 2000 John Wiley & Sons, Ltd.