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Photochromic Amorphous Molecular Materials: Acceleration Effect of cis-trans Thermal Isomerization of 4-[Bis(9,9-dimethylfluoren-2-yl)amino]azobenzene as Amorphous Film
Takahiro Tanino, Toru Takahashi, Hideyuki Nakano and Yasuhiko Shirota

We have performed studies of the creation of photochromic amorphous molecular materials and investigated their photochromic properties as amorphous films in comparison with those in solution. In the present study, we have investigated the photochromic reaction of an azobenzene-based photochromic amorphous molecular material, 4-[bis(9,9-dimethylfluoren-2-yl)-amino]azobenzene (BFlAB), and found that the backward cis–trans thermal isomerization of the photogenerated cis-isomer of BFlAB as amorphous film is accelerated relative to that in solution and that this acceleration effect becomes much more prominent as the irradiation time for generating the cis-isomer decreases. The results indicate that the local free volume of the amorphous film gradually increases during the repeated trans–cis and cis–trans photoisomerizations of the azobenzene chromophore.

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