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Abstract
We have succeeded in forming highly oriented poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2) layers by using photo-aligned polyimide films. The polyimide (Azo-PI) contains azobenzene in the backbone structure, which allows us to optically control the alignment of the backbone structure. The photo-aligned Azo-PI films were stable to xylene (a solvent of F8T2) and to annealing at a liquid-crystalline temperature of F8T2. After annealing at 285°C for 15 min followed by quenching to room temperature, the ∼20 nm-thick F8T2 layer on the photo-aligned Azo-PI film showed a dichroic ratio of ∼14 at 490 nm (the absorption maximum), indicative of a high degree of alignment of F8T2. We conclude that the photo-aligned Azo-PI films are proper alignment films for F8T2.
Acknowledgments
We would like to thank K. Yase, R. Azumi, Y. Yoshida, M. Chikamatsu, and M. Misaki of Photonics Research Institute of National Institute of Advanced Industrial Science and Technology (AIST) for their valuable discussion. We would also like to thank S. Murata, J. Yokota and N. Narita of Chisso Co. Ltd. for supplying the Azo-PAA solution and for performing the GPC measurements. We thank T. Nakanishi for support of the TGA measurement, and J. H. G. Owen for helpful comments on the manuscript. This work was supported in part by a Grant-in-Aid for Exploratory Research from the Ministry of Education, Culture, Sports, Science and Technology (#17656010), by a Grant-in-Aid for Scientific Research (B) from Japan Society for the Promotion of Science (#18360012), and by a grant from the Iketani Science and Technology Foundation (#0171118-A).