Polyimide photo-alignment films applicable to poly[ (9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene]

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 jl ylene (a solvent of F8T2) and to annealing at a liquid-crystalline temperature of F8T2. After annealing at 285 degrees C for 15 min followed by quenching to room temperature, the similar to 20 nm-thick F8T2 layer on the photo-aligned Azo-PI film showed a dichroic ratio of similar to 14 at 490nm (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.