*e-mail: khopark@kist.re.kr 1598-5032/12/431-06 ©2003 Polymer Society of Korea 431 Macromolecular Research, Vol. 11, No. 6, pp 431-436 (2003) Synthesis and Characterization of a New Photoconducting Poly(siloxane) Having Pendant Diphenylhydrazone for Photorefractive Applications Sang Ho Lee, Woong Sang Jahng, and Ki Hong Park* Optoelectronic Materials Research Center, Korea Institute of Science and Technology, P. O. BOX 131, Cheongryang, Seoul 136-791, Korea Nakjoong Kim and Won-Jae Joo Department of Chemistry, Hanyang University, Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea Dong Hoon Choi College of Environment & Applied Chemistry, Kyunghee University, Younginn, Kyungki-do 449-701, Korea Received Apr. 16, 2003; Revised Sept. 27, 2003 Abstract: A new photoconducting polymer, diphenyl hydrazone-substituted polysiloxane, was successfully syn- thesized by the hydrosilylation method and characterized by FT-IR, 1 H-NMR, and 29 Si-NMR spectroscopy. The glass transition temperature (T g ) of the polysiloxane having pendant diphenyl hydrazone was ca. 62 ο 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 C 60 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 (∆n = 2.6 10 -3 at 50 V/μm) and a high diffraction efficiency of 81% at an electric field of 40 V/μm. Keywords: photorefractive, diphenyl hydrazone, polysiloxane, photoconducting, hydrosilylation. Introduction The photorefractive effect was first reported with LiNbO 3 crystal more than 35 years ago. 1 A variety of potentially important applications have been proposed using inorganic crystals, including high-density optical data storage, image processing, phase conjugation, beam fanning limiter, and optical correlator. 2 However, because of difficulties in crys- tal growth and sample preparation, inorganic crystals have been limited for mass production. For last decade, extensive studies have been carried out on organic photorefractive materials to overcome some of problems associated with inorganic materials. Photorefractive organic materials have many advantages of lower dielectric constants, lower cost, and easier processing than inorganic materials. Among many organic photorefractive materials reported to date, polymeric host-guest system has been extensively investigated because of their excellent photorefractive prop- erties, compositional flexibility and easy fabrication method. 3,4 The charge-transporting polymers such as poly(vinyl carba- zole) or poly(siloxane carbazole), doped with nonlinear optical chromophores have been generally adopted due to their excellent photorefractive performance. The large refractive index modulations, up to ∆n = 10 -2 , and fast response times, down to 1 ms, have been reported with this polymeric sys- tem. 5-8 Carbazole-substituted polysiloxane (PSX-Cz) is one of the most well-known photoconducting polymers for photore- fractive systems. 9 The glass transition temperature (T g ) of these PSX-Cz composites could be lowered to room tem- perature simply by adding a NLO chromophore. It was notable that the photorefractive properties could be improved by using a low T g polysiloxane because this system did not contain inactive molecules such as a plasticizer. 10 In this study, a new photoconducting poly(siloxane) with pendent 4-(N,N-diethylamino)benzaldehyde diphenylhydra- zone (DEH) was synthesized by a hydrosilylation reaction. The DEH-doped polymer has been reported as a good can- didate with excellent hole-mobility and photorefractivity. 11-13