Time-resolved fluorescence study on the mechanism of polarizing energy transfer in uniaxially oriented polymer blends

Abstract

A time-resolved study of polarizing energy transfer in oriented blends of a conjugated polymer [a dialkoxy-substituted poly(p-phenyleneethynylene) derivative] and an organic laser dye (7-diethylamino-4-methylcoumarin) in ultra-high molecular weight polyethylene is presented. The transfer is described in terms of a Förster mechanism, based on long-range dipole–dipole interactions. Förster radii were determined in oriented blend films and in chloroform solutions. It was found that the transfer process is critically influenced by the phase behavior of the system under investigation. A depolarizing homotransfer between donor molecules was found to be a key step in the polarizing nature of the transfer which, ultimately, allows excitation light polarized perpendicularly to the film orientation direction to be emitted with the polarization direction parallel to its orientation.