Absorption and fluorescence properties of p-substituted stilbenes in poly(vinyl chloride) film

Experimental studies have demonstrated that the absorption and fluorescence spectra of linear molecules with one double bond, i.e. 4-amino-4'-nitrostilbene (ANS), 4-dimethylamino-4'-nitrostilbene (DNS) and 4,4'-diphenylstilbene (DPS), contained in preheated to 393 K or nonheated poly(vinyl chloride) (PVC) films are identical in shape and position, unlike those observed for ANS, DNS and DPS in poly(vinyl alcohol) (PVA) films. For polar ANS and DNS molecules in PVC film a decrease in the emission anisotropy with growing wavelength of the fluorescence band was observed. This unusual behaviour of the emission anisotropy is accounted for by the overlap of two close emission bands from different luminescent centres, resulting from different microenvironments of the ANS and DNS molecules in PVC film. The emission anisotropy of nonpolar DPS molecule in PVC does not change within the fluorescence spectrum.