POLARIZED ABSORPTION AND EMISSION-SPECTRA OF STILBAZOLIUM MEROCYANINES

Natural light and polarized absorption and fluorescence spectra of six stilbazolium merocyanines (with different side groups and molecule lengths) embedded in polyvinyl alcohol film were measured. In a stretched film, dye molecules are highly oriented. Different spectra are obtained for the same dye in isotropic and anisotropic polymer films. Conclusions concerning the degree of dye orientation and the distribution of molecules in the direction of film stretching are made on the basis of different combinations of polarized fluorescence components. Dyes occur in the polymer matrix in protonated and free base forms. The protonation of merocyanines molecules influences their degree of orientation in an anisotropic matrix and the aggregation of the dye. Aggregation of protonated and free base forms competes with the interaction of the dye with the matrix. Aggregates are oriented in a different way from monomers. The side groups attached to the dye chain have a strong influence on the orientation of the molecules and their aggregation properties. © 1990.