Excitation energy migration in uniaxially oriented polymer films: A comparison between strongly and weakly organized systems

The mechanism of multistep excitation energy migration in uniaxially oriented polymer films is discussed for strongly and weakly orientating dyes in poly(vinyl alcohol) matrix. The comparison between both types of systems is based on concentration depolarization of fluorescence, Monte-Carlo simulations and linear dichroism data. It is found that the alignment of transition dipole moments of fluorophores in the ordered matrix relative to the direction of polymer stretching exhibits strong effect on the concentration depolarization of fluorescence. In ordered matrices of flavomononucleotide and rhodamine 6G concentration depolarization of fluorescence remains quite strong, whereas for linear carbocyanines it is very weak despite effective energy migration.