Depolarizing energy transfer in photoluminescent polymer blends

The occurrence of a depolarizing polarizing energy transfer effect is demonstrated in uniaxially oriented polymer blend films. These blends are based on ultra-high molecular weight polyethylene as the matrix polymer, and additionally comprise 1,4-bis{(2-ethylhexyloxy)phenylethynyl} benzene (EHO-BPB) as a sensitizer, and either a regioregular HT sexi(3-n-octylthiophene) (6OT) or 7-(dimethylamino)-4-(trifluoromethyl) coumarin (C152) as emitter. The EHO-BPB sensitizer molecules are highly oriented in tensile-deformed blend films, and, thus, cause a highly anisotropic, i.e. linearly polarized optical absorption. The absorbed energy is, subsequently, transferred to the emitter molecules, which are essentially unoriented and, consequently, emit unpolarized light.