13 November 2000 Toward morphologically stable photorefractive composites: a comparative study of ATOP/PVK-based materials
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For the highly dipolar merocyanine chromophore ATOP, which exhibits a high polarizability anisotropy, material related properties were optimized by substituent variations at four different positions of the pr-conjugated core. Differential scanning calorimetry (DSC) and solubility studies in the model solvent N,N'-dimethylaniline showed a significant influence of the substituents. Thus almost unlimited solubility in N,N'-dimethylaniline and the formation of kinetically stable amorphous glasses was observed for the dye ATOP—4 whereas the parent dye ATOP—5 was a high melting and almost insoluble solid. The more soluble and lower melting derivatives ATOP—3, ATOP—4, ATOP—8 and ATOP—9 all showed a high compatibility with the photoconducting polymer poly(N-vinylcarbazole) which allowed to prepare composites containing up to 50 %wt of the respective dye. For these composites pronounced photorefractive effects were measured with index modulation ofup to zln 7 x iO and gain coefficients ofup to r= 180 cm1 at electrical fields ofonly E —35 V.tm I For the composites of ATOP—4 no evidence for crystallization or phase-separation could be observed over several months, demonstrating that also host-guest systems containing highly dipolar dye molecules may be optimized towards high morphological stability.
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Erwin Mecher, Erwin Mecher, Francisco Gallego-Gomez, Francisco Gallego-Gomez, Christoph R. Braeuchle, Christoph R. Braeuchle, Klaus Meerholz, Klaus Meerholz, Ruediger W. Wortmann, Ruediger W. Wortmann, Sheng Yao, Sheng Yao, A. Sautter, A. Sautter, Frank Wuerthner, Frank Wuerthner, } "Toward morphologically stable photorefractive composites: a comparative study of ATOP/PVK-based materials", Proc. SPIE 4104, Organic Photorefractives, Photoreceptors, and Nanocomposites, (13 November 2000); doi: 10.1117/12.406476; https://doi.org/10.1117/12.406476

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