Characteristic changes of vapor deposited films for bis-styrylbenzene derivatives after thermal treatment

This report describes change in the characteristics of vapor deposition films for bis-styrylbenzene derivatives (BSDs) after thermal treatment. The compounds employed in the present study were trifluoromethyl-group substituted BSDs: E,E-1,4- bis(2-trifluoromethylstyryl)benzene, (2-CF3), E,E-1,4-bis(3-trifluoromethylstyryl)benzene, (3-CF3), and E,E-1,4-bis(4- trifluoromethylstyryl)benzene, (4-CF3). The fluorescence spectra and the morphologies of the evaporated films of 2-CF3 changed depending on the thermal treatment temperature. As-evaporated film was aggregation of micron size crystalline domains. After thermal treatment at 100°C for 30 min, these changed into a long rectangular parallelepiped crystals suggesting that structural order has increased. Meanwhile, the optical properties and crystalline structures of the evaporated 3-CF3 films did not change even after thermal treatment at 110°C for 30 min. In the case of 4-CF3, the fluorescence spectrum of the evaporated film shifted to the shorter wavelength side after the thermal treatment. From the results of X-ray diffraction, the evaporated film showing crystallinity decreased in the structure orderliness by thermal treatment at 170°C for 30 min.