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

A time-resolved study of polarizing energy transfer in oriented blends of a conjugated polymer [a dialkoxy-substituted poly(p-phenyleneethynylene) der ivative] and an organic laser dye (7-diethylamino-4-methylcoumarin) in ultr a-high molecular weight polyethylene is presented. The transfer is describe d in terms of a Forster mechanism, based on long-range dipole-dipole intera ctions. Forster radii were determined in oriented blend films and in chloro form solutions. It was found that the transfer process is critically influe nced by the phase behavior of the system under investigation. A depolarizin g homotransfer between donor molecules was found to be a key step in the po larizing nature of the transfer which, ultimately, allows excitation light polarized perpendicularly to the him orientation direction to be emitted wi th the polarization direction parallel to its orientation.