Effects of alkyl subsistents of photorefractive chromophores on electro-optic response

POLY 519

Chil-Sung Choi, sevenstar@ihanyang.ac.kr, Quoc vuong Nguyen, Jin-Woo Oh, Ui-Jung Hwang, and Nakjoong Kim. Department of Chemistry, Hanyang University, 36-344 17-Haengdang-dong, Seongdong-gu, Seoul, 133-791, South Korea
Photorefractive (PR) effect refers to a spatial modulation of refractive index of materials which possess both photoconductivity and optical nonlinearity simultaneously. As two coherent beams intersect a photorefractive material, the internal space-charge field is formed due to redistribution of photo-generated charges, which subsequently modulate refractive index of the material via an electro-optic effect. The polymeric photorefractive materials with low glass transition temperature exhibit two attractive features, the large refractive index modulation and the optical erasability of recorded holographic information. The molecular orientational enhancement in photorefractive material is directly related with a rotational mobility of the electro-optic chromophores. The alkyl subsistents in photorefractive chromophore are expected to provide the free volume to each chromophore, which allow fast rotational mobility to give fast response upon external applied electric field. We synthesized 4-piperidinobenzylidene-malononitrile (PDCST) derivatives with various alkyl subsistents, such as methyl, ethyl and isopropyl and investigated the effcet of alkyl groups attached to chromophore on electro optical properties and response time.