Isomerization of Diphenyl Polyenes. Part II. Fluorescence Properties of l,8-Diphenyl-l,3>5,7-octatetraene in Poly (vinyl alcohol) Film

The effect of temperature on the fluorescence properties of l,8-diphenyl-l,3,5,7-octatetraene (DPO) in polyvinyl alcohol) film (PVA) was investigated in the range from 295 to 428 K. Upon heating above 353 K, the quantum yield of D P O increases rapidly. This effect is irreversible, similarly as the optical density in the long wavelength absorption band (320-440 nm). It has its origin in the cis-trans conversion of D P O molecules in PVA film at high temperatures. The behaviour of the fluorescence anisotropy in the same temperature range was also investigated. The emission anisotropy was found to be a viscosity indicator in the microenvironment of the D P O molecules in PVA film.